FINAL EXAM FINAL QUIZLET - ATM 1050

inflow

"suck zone" - influx of moisture rich air into a mesocyclone

medium range forecast

3 - 5 days

tropical storm

A region of organized thunderstorms over the tropical or subtropical ocean with a cyclonic wind circulation between 35 and 64 knots.

When are surface winds generally the strongest and most gusty?

Afternoon

Continental tropical (air mass)

An air mass characterized by high temperatures and low humidity.

polar low

An area of low pressure that forms over polar water behind (poleward of) the main polar front.

_______ air moves from the poles toward the ________

Cold, equator

Low pressure flow is

Counter-clockwise

_______ air moves from the equator toward the ________

Hot, poles

Lines of equal pressure on a weather map are called

Isobars

sheet lightning

Occurs when the lightning flash is not seen but the flash causes the cloud (or clouds) to appear as a diffuse luminous white sheet.

Explain how a nonsupercell tornado, such as a land-spout, might form.

Rapidly increasing wind speed with height provides vertical wind speed shear and the changing wind direction with height -- from southerly at at low levels to westerly at high levels -- provides wind direction shear, which induces the updrafts inside the storms to rotate.

source regions (for air masses)

Regions where air masses originate and acquire their properties of temperature and moisture.

Low pressure means what kind of weather?

Stormy weather

cyclogenesis

The development or strengthening of middle-latitude (extratropical) cyclones.

What is frontolysis?

To weaken a front, decrease the temperature difference across the front

Low pressure flow is:

counter-clockwise

Greater PGF=

stronger PGF

"skill of this method drops dramatically with time"

trend method

What does Anemometer measure?

wind (speed only), cups on a pole spin around faster in a stronger wind

​On weather maps cold fronts are drawn

​In blue, with arrowheads showing the front's general direction of movement

​Wind direction is

​The direction from which the wind is blowing

In terms of the three-cell model of the general circulation, areas of surface low pressure should be found at​

​The equator and 60° latitude

What makes carbon dioxide unique (as well as extremely influential to climate change)?

*Carbon Dioxide has a residence time of thousands of years while other trace gasses have residence times much shorter. *With this longer time in the atmosphere, the amount of radiation it absorbs and ultimately warms the atmosphere with increases

circular MCS

- covers many states - severe weather - heavy rain producers

linear MCS

- very strong winds - isolated, quick tornadoes

The forces that affect the horizontal movement of air

-Gravitational -Frictional -Coriolis

"back door" cold front

A cold front moving south or southwest along the Atlantic seaboard of the United States.

cap

A layer of warm, dry, stable air that inhibits warm, moist, unstable air from rising through it to produce thunderstorms.

forecast funnel

A sequence of steps used by forecasters to analyze current and projected conditions, moving from larger to smaller scales during the process.

How does a tornado watch differ from a tornado warning?

A tornado watch alerts the public that tornados may develop. A tornado warning means a tornado has already been spotted.

maritime polar (air mass)

An air mass characterized by low temperatures and high humidity.

Where is climate change most apparent?

At the poles and at glaciers

A dry line is

Both a dew point front and a boundary marking a strong horizontal change in atmospheric moisture

What is the approximate global concentration level of atmospheric carbon dioxide?

Carbon dioxide makes up only 0.039% of the composition of the atmosphere

High pressure flow is

Clockwise

Air Pressure Differences:

Creates Wind (causes the wind to blow)

weather symbols

Drizzle: ' Moderate Drizzle: ''' T-Storm : look up Rain: . Moderate Rain: ... Funnel Cloud: )( Snow: * Moderate snow: ***

Wind gusts are caused by

Eddies

True/False: During the Ice Crystal process Ice crystals grow larger at the the same time that water droplets grow larger.

FAlSE

High pressure means what kind of weather?

Fair weather

T/F. The Coriolis is what causes wind to blow

False

An offshore wind blows

From land to water

GFS

Global Forecast System (numerical modeling)

Good source regions are dominated by:

High pressure

If the Earth did not rotate, the wind would blow directly from regions of _____ pressure toward regions of _____ pressure

High, low

What will cause an ice Crystal to fall in a cloud?

Ice Crystals will begin to fall from clouds when the Crystal becomes SIGNIFICANTLY LARGE

The jet stream flows​

In a wavy pattern from West to East

A condition where the central and eastern tropical Pacific Ocean turns cooler than normal is called​

La Niña

What type of upper-level flow (meridional or zonal) aids in cyclonic formation at the surface?

Meridional flow aloft leads to cyclonic activity intensifying

persistence forecasts

Predict that future weather will be the same as the current weather.

weather forecasting

Predicting how the present state of the atmosphere will change over a period of time

The scale on an altimeter indicates altitude, but an altimeter actually measures:

Pressure

What is proxy data and what are its various sources?

Proxy data is data gathered from natural recorders of climate variability Sources include: Seafloor sediments Oxygen-Isotope Analysis Glacial Evidence Tree Rings Fossil Pollen Historical Documents Corals

What produces the rain shadow effect?

Sinking and Warming air on the leeward side (Other side) of a mountain - Because of air compression

A rapid change in pressure over a relatively short distance is called a ____ pressure gradient.

Steep

Stronger PGF=

Stronger wind

Where would temperatures be moderate? Where would there be large ranges in temperature?

Temperatures are moderate in coastal climates, while larger temperature ranges are found in continental climates.

Why is the central part of the United States more susceptible to tornadoes than any other region of the world?

The Central Plains region is most susceptible to tornados because it provides the proper atmospheric setting for the development of the severe thunderstorms that spawn tornadoes. Here (esp. in spring), warm, humid, surface air is overlain by cooler, drier, air aloft, producing a conditionally unstable atmosphere. When a strong vertical wind shear exists and the surface air is forced upward, large thunderstorms capable of spawning tornadoes may form.

Absolutely Stable Atmosphere Occurs when...

The Environmental Lapse Rate (ELR) falls Below both the Dry and Moist Adiabatic Rates - Air parcel will be warmer and less dense than the surrounding air and will rise due to buoyant forces. - Clouds with extensive vertical development are indicative of absolute instability.

Whats the difference between the polar and subtropical jet streams? Where are each located? (north vs. south)

The Polar Jet is Arctic Air and Affects us in Winter Season. The Sub-Tropical Jet is Warmer Air, Brings in Moisture, and Affects us in Spring & Summer. The subtropical jet is southern and the polar front jet is northern.

dart leader

The discharge of electrons that proceeds intermittently toward the ground along the same ionized channel taken by the initial lightning stroke.

dissipating stage

The final stage in the development of an ordinary cell thunderstorm when downdrafts exist throughout the cumulonimbus cloud.

Air Pressure:

The mass of air above a given level

How did the Greeks classify world climates?

They divided each hemisphere into three zones: torrid, temperate, and frigid

T/F. Storms rank in size from largest to smallest as follows: Middle-latitude cyclonic storm, hurricane, thunderstorm, tornado

True

T/F. The difference in surface wind speed between morning and afternoon is typically greater on a clear, sunny day than on a cloudy, overcast day

True

T/F. The pressure gradient force has a direct effect on horizontal wind movements

True

A wind reported as: 265 degrees at 15 kts, means:

WSW at 15 kts

With the Coriolis Force what does wind do in the S Hemisphere?

Wind deflects to the left in the south hemisphere

With the Coriolis Force what does wind do in the N Hemisphere?

Wind deflects to the right in the north hemisphere

What is the difference between a hurricane, a tropical storm, and a tropical depression?

Wind speed! Tropical Depression = Wind speeds ≤ 39 mph Tropical Storm = Wind speeds between 39 and 73 mph Hurricane = Wind speeds ≥ 74 mph

​What is an example of mesoscale motion?

Winds blowing through a city

How are sea level and ocean pH levels affected by climate change?

With climate change comes sea level rise from thermal expansion and melting of glaciers When CO2 dissolves in water it creates carbonic acid and thus drops the ocean's pH level

Under what condition(s) may an occluded front form?

as a cold front overtakes a warm front

numerical modeling predictions come from

computer models

3. prediction

figure things out/make your forecast

how is thunder produced

from the rapidly expanding heated air along the channel of the lightning stroke

Where is warm advection most likely to occur?

from the surface up to the 500-mb level ahead of an advancing warm front

What is a rotating column of air that remains aloft and does not touch the ground often called?

funnel cloud

Closer isobars=

greater PGF

Flowing northward along the east coast of the United States is a tremendous warm water current called the ____________________.​

gulf stream

Cool air at the surface= ______ pressure

high

Air will flow from _______ pressure to areas of ________ pressure. Why is that?

high; low because heating or cooling a column of air can cause air aloft to move horizontally from the warmed column to the cooled column

What do blue "H"s indicate on a weather map?

higher pressure areas (anticyclones), fair weather, clockwise flow of air

Heating or Cooling a column of air will establish _______ variations in air pressure.

horizontal (west/east)

a microburst is located

in a strong downdraft area

Wind blowing with sufficient force to rip the roof off buildings:

is uncommon

What is the Synoptic Scale?

large scale, includes high and low pressure systems and hurricanes, 500-2,000 km, lasts days to weeks

What is the Planetary Scale?

largest scale, includes longwaves in the westerlies, lasts weeks or more

When are lake-effect snows best developed around the Great Lakes?

late fall and early winter when cold, dry polar air moves over the relatively warm water

What is a squall line?

line of multicell thunderstorms

What are isotachs and jet streaks?

lines of equal wind speed higher-velocity winds within the jet stream

Rossby waves are also known as

longwaves

Cold air aloft is associated with ________ atmospheric pressure.

low

Warm air at the surface= ______ pressure

low

What do red "L"s indicate on a weather map?

lower surface pressure (mid-latitude cyclones or depressions), weather is unsettled, counterclockwise flow of air

Pressure at the center of a hurricane is ______ than the surroundings at the surface and ______ than the surroundings aloft.

lower, higher

Warm, humid, and a chance of thunderstorms is a typical weather pattern produced by an air mass designated as ____________________.

mT

What type of air mass would be responsible for hot, muggy summer weather in the eastern half of the United States?

mT

In which hemisphere(s) do hurricane winds rotate in a clockwise direction?

southern hemisphere only

What are the characteristics of the cold belt of the Conveyor Belt Model?

starts at surface ahead (north) of warm front flows westward towards low pressure center flows beneath warm conveyor belt convergence cause conveyor belt to ascend therefore, also induces precipitation

Which forecasting method assumes that weather systems will move in the same direction and at the same speed as they have been moving?

steady state (trend) forecasting

lee side lows are

storms (extratropical cyclones) that form on the eastern (lee) side of a mountain range

Low pressure means:

stormy weather

Isobars and height contours are rarely straight ____________

straight (they bend and curve)

In an air mass, which two properties are similar at any given horizontal direction and at any given altitude?

temperature and moisture

Which general circulation feature is not associated with the tropical atmosphere?

the Ferrell cell

What does Radiosonde measure?

the instrument package on a pilot balloon designed to measure: Temperature Humidity Pressure Wind Dew Point

When upper-level divergence of air above a surface low-pressure area is stronger than the convergence of surface air, which of the following will occur?

the surface pressure will decrease and the storm itself will intensify

persistence forecasting works best in

the tropics

a weather watch would probably be issued for what conditions?

there is a chance for tornadoes tomorrow

Know and understand Mountain and Valley Breezes

thermal circulation, (valley breeze= anabatic wind) (mountain breeze= gravity wind)

Longwaves in the middle and upper troposphere usually have lengths on the order of how many kilometers?

thousands of kilometers

Atmospheric shortwaves usually move ____ at a speed that is ____ than longwaves

west to east, faster

Due to Hadley cell formation and the Coriolis force in both hemispheres, winds aloft flow:

westerly

Near the ITCZ:

wet , warm, jungles

Near the Sub-Polar Lows:

wet, cold, forests

persistence forecasting

what happened yesterday will likely happen today

When do frontal systems mostly occlude?

when the Low Pressure system is strong

Ordinary thunderstorms only last about one hour. When do they begin to dissipate?

when the downdraft spreads throughout the cloud and cuts off the updraft

According to the model of the life cycle of a wave cyclone, the storm system is normally most intense

when the system first become occluded

What does Aerovane measure?

wind (speed and direction) points into the wind to give direction and propeller spins to give speed

Doppler radar is helpful for measuring precipitation and

wind speed --- Calculates total precipitation in a given amount of time by using precipitation intensity

What do Automated Surface Observing Systems (ASOS) measure?

wind speed and direction, temperature and dew point, air pressure

Under which condition could a persistence forecast be quite accurate?

you are positioned in the middle of a large stationary air mass

How do tornadoes form? How do hurricanes form? What is needed for each to occur? On average (over the entire U.S.), when do they occur?

"Ingredients" needed for a tornado to form: *Moisture Instability Mixing *Extends downward from cumulonimbus cloud as a funnel cloud until it makes contact with the ground, then it officially becomes a tornado *Tornadoes can form along squall lines, cold fronts, and typical cyclones; however the most intense tornadoes come from supercells or mesocyclones. *Occurs most common in late spring and early summer *Hurricane = an intense low pressure system that forms over tropical or subtropical oceans and are characterized by intense convective (thunderstorm) activity and strong cyclonic circulation *Form in the tropical oceans across the world with the exception of the South Atlantic and Eastern South Pacific *occurs when huge quantities of water vapor condense - large quantities of warm moist air needed as well as Sea-surface Temperatures reach 80°F or higher and Coriolis force to initiate rotation *Most occur in August, September, and October

What is the ITCZ and how does it relate to the three cells above?

"Intertropical Convergence Zone" -area of lower pressure with convergence of air and rising motion (lots of thunderstorms and rain) Found along the equator- always. Result of trade winds converging in one location

ordinary cell (air mass) thunderstorms

(also called air-mass thunderstorm) A thunderstorm produced by local convection within a conditionally unstable air mass. It often forms in a region of low wind shear and does not reach the intensity of a severe thunderstorm.

conveyor belt model

(for mid-latitude storms) A three- dimensional picture of a mid-latitude cyclone and the various air streams (called conveyor belts) that interact to produce the weather associated with the storm.

What are the characteristics of the dissipating stage of an air mass thunderstorm?

*Dominated by downdraft The vacating air and precipitation from the downdraft encourage entrainment of dry air, weakening the updraft. Without a supply of moisture from the updraft the cloud will eventually completely evaporate. Only 20% of moisture that condenses in an air-mass thunderstorm actually leaves the cloud as precipitation. The remaining 80% evaporates back into the atmosphere

What are the characteristics of the cumulus stage of an air mass thunderstorm?

*Dominated by updraft Uneven heating of the surface leads to rising air currents. At first buoyant parcels produce fair- weather cumulus clouds which grow vertically. Once the cloud passes beyond the freezing level, the Bergeron process begins producing precipitation. Eventually the accumulation of precipitation is too great for the updrafts to support

How do rainbows form?

*It is the result of refraction and internal reflection in a raindrop *The white light is refracted and separated into the visible spectrum colors after entering the raindrop *Primary rainbow is the result of one internal reflection *Secondary rainbow is the result of two internal reflections

What are some characteristics of glories?

*Light is altered same as with rainbows but raindrops are much smaller and more uniform *Light reflected directly back towards sun *Most commonly seen from airplanes

What are two types of satellites used for weather analysis? What are some characteristics of each?

*Polar Satellites: Orbit Earth at relatively low altitudes (about 850 kilometers) Circle Earth in a north-to-south direction As Earth rotates, these satellites drift ~15° westward during each orbit. Allows to a global image of the entire Earth twice a day *Geostationary Satellites: Orbit Earth at much higher altitudes (35,000 kilometers) Remain fixed over a point on the Earth because their rate of travel keeps pace with Earth's rotation. At this altitude, some detail is lost in the imagery

What are the characteristics of the mature stage of an air mass thunderstorm?

*Supports both up and down drafts Precipitation begins to fall which causes drag on the air and initiates a downdraft. Once the downdraft leaves the base of the cloud, precipitation in released, marking the beginning of the mature stage. Downdrafts exist side by side with updrafts and the cloud grows. The cloud grows to the tropopause, spreading the updraft laterally and producing the characteristic anvil top.

Explain the phenomenon of the classic "wet road" mirage? How is light traveling? What are you actually seeing? What type of mirage is this?

*The "wet road" mirage is an inferior mirage which occurs when images appear below the true object location *Results from the refraction (bending) of light due to densities of different mediums *You're actually seeing a reflection of the sky

Who can and cannot issue weather watches and warnings? Give examples of each.

*The NWS is the OFFICIAL voice in the U.S. for issuing watches and warnings during hazardous weather situations. *Private sector meteorologists (The Weather Channel, etc.) DO NOT issue watches/warnings **The Storm Prediction Center (SPC) in Norman, OK issues tornado watches. **The National Hurricane Center (NHC) in Miami, FL issues hurricane watches and warnings.

How do we rank the intensities of tornadoes and hurricanes? What variables do we look at for each hazard?

*The National Weather Service uses the Enhanced Fujita Scale (EF-Scale) to classify different tornado classes. **Wind speeds are determined by surveying the damage caused by the tornado after it has occurred *Saffir-Simpson Scale: Established to rank relative intensities of hurricanes. **Category based on observed conditions of PRESSURE and WIND SPEEDS Can change through time Viewed as estimates of the amount of damage it would cause if it made landfall right now

Understand Parcel Theory. What is unstable vs stable air? How does a parcel of air compare to the surrounding environment for each, stable or unstable? How do their densities differ? What does the parcel of air want to do (rise or sink) if unstable vs. stable? What type of precipitation would there be with unstable vs. stable air? How do air parcels cool or warm?

*Unstable air: a parcel of air is warmer than its surroundings and thus wants to rise **less dense parcel ***Clouds are towering, cumulus, and accompanied by heavy rain. When cauliflower-shaped clouds appear, bubbling upward, atmosphere is unstable, precipitation can be heavy downpour of rain *Stable air: the parcel of air is cooler than its surroundings and does not want to rise - it wants to sink **more dense parcel ***Any clouds that form are stratus and lack vertical structure and any precipitation is light to moderate *Parcels cool and condense when they rise and warm and expend when they sink

What is the difference between visible, infrared, and water vapor imagery from satellites?

*Visible: similar to what the human eye would, obtained by the sunlight reflected from Earth (limited to daytime only). Useful for identifying cloud shapes, organizational patterns, and thickness. *Infrared: obtained by radiation emitted (rather than reflected) from the same objects, measures cloud-top temperatures (or ground if no clouds). Useful for determining which clouds are producing heavy precipitation and storminess. *Water Vapor: shows moisture concentrations in the atmosphere. Most of Earth's radiation with a wavelength of 6.7 micrometers is emitted by water vapor. Valuable tool for locating frontal boundaries

Under the Köppen Classification system, how are climates types classified? What are the first order classes? Characteristics of first order classes? How many subclasses could there be?

*temperatures and precipitation *1st order classes: A: Equatorial - Tropical B: Arid/Dry - Desert C: Warm Temperature/Continental - Subtropical/Marine D: Snow - Subarctic E: Polar - Polar *There are 3 classes

Which of the following statements best describes a wave cyclone?

- It produces a cold and warm front. - It develops a region of low pressure. - It is associated with a region of warm air to the south of the wave's apex.

MOS pros

- easy to get numbers - great for hour by hour forecasts - great for comparison techniques

What can cause errors in forecasts made by numerical weather prediction models?

- flaws in the computer models - errors that creep in along model boundaries - sparseness of meteorological data - inadequate representation of pertinent meteorological processes

Thickness charts help forecasters

- identify air masses - locate fronts - predict daily maximum and minimum temperatures - predict whether falling precipitation will be rain or snow

key points to remember when predicting weather

- its always better (initially) to be conservative - be confident, but don't promise anything

shelf clouds

- not severe just plain scary looking!

By examining a surface map, the movement of a surface low-pressure area can be predicted based upon the

- orientations of the isobars in the warm sector - region of greatest pressure decrease - movement during the previous six hours

variables of numerical modeling

- pressure - temperature - winds - humidity - clouds - precipitation

MOS cons

- too easy to use without any other method - sometimes bad initial conditions - results in inaccurate output

Which statement is true of vorticity

- vorticity can be observed by satellites, even during cloudy conditions - planetary vorticity is always present - relative vorticity can be either positive or negative

What condition(s) are necessary ingredients for tropical cyclone formation?

- warm sea surface temperatures (usually above 80°F) - less wind shear in the troposphere as height increases - an incipient cyclonically rotating disturbance - warm, moist inflow

Under which condition would a hurricane dissipate?

- when it moves over colder water - when it moves over land - when the surface inflow of air exceeds upper-level outflow of air

where might lightning occur?

- within a cloud - from a cloud to the ground - from one cloud to another could

How do downdrafts form in ordinary cell thunderstorms?

-As the cloud builds well above freezing level, the cloud particles grow larger. -Cloud particles also become heavier. -Eventually rising air can no longer keep them suspended and they begin to fall. -While this takes place, drier air from around the cloud is being drawn into it in a process called entrainment. -Entrainment of drier air causes some raindrops to evaporate, which chills the air. -The air is now colder and heavier than the air around it and thus begins to descend as a downdraft. -Downdraft may be enhanced as falling precipitation drags some of the air along with it.

(a) Describe how a microburst forms. (b) Why is the term horizontal wind shear often used in conjunction with a microburst?

-Beneath an intense thunderstorm, the downdraft may become localized so that it hits the ground and spreads horizontally in a radial burst of wind, much like water pouring from the tap and striking the sink below. Such downdrafts are called downbursts. -A downburst with winds extending only 4 km or less is a microburst. In the area of a microburst, rapid changes in wind speed or wind direction (wind shear) pose a serious hazard to aircraft.

What atmospheric conditions are necessary for a multi cell thunderstorm to form?

-Cold downdraft of mature and dissipating thunderstorms, upon reaching the surface, may force warm, moist surface air upward along its advancing edge. -This rising air then condenses and builds up into a new thunderstorm. -Process may repeat over and over as old cells die out and new ones form. -Thus, it's entirely possible for a series of thunderstorms to grow in a line, one next to the other, each in a different stage of development. -Thunderstorms that form in this manner are termed multi-cell thunderstorms. -Most ordinary storms are multi-cell thunderstorms, as are many severe thunderstorms.

What is a current problem with modern-day weather predictions?

-Computer forecast models make assumptions about the atmosphere that are not always correct. -There are regions of the world where only space observations are available. -Computer models do not always adequately interpret the surface's influence on the weather. - The distance between grid points on some models is too large to pick up smaller-scale weather features such as thunderstorms.

What is the difference between an HP supercell and an LP supercell?

-HP Supercells (High Precipitation): often produce extreme downdrafts (downbursts), flash flooding, and very large hail. If tornados are present, it is very difficult to see them, as they often form in the area of heavy precipitation. -LP Supercell (Low Precipitation): supercell characterized by little precipitation

Describe the atmospheric conditions at the surface and aloft that are necessary for the development of most supercell thunderstorms. (Include in your answer the role that the low-level jet plays in the rotating updraft)

-If the winds aloft become even stronger (strong shear) and change direction with height (from more southerly at the surface to more westerly with aloft), the storm may move in such a way that the outflow of cold air from the downdraft never undercuts the updraft. -The wind shear may be strong enough to create horizontal spin, which when tilted into the updraft causes it to rotate. -In this situation, the thunderstorm may grow into a larger, longer-lasting (longer than an hour) severe storm called a supercell that has a violent updraft and a single cell.

short range forecast

1 - 3 days

Give two examples of vertical wind shear.

1. Change of wind speed with altitude, 2. Change of wind direction with altitude.

What are the steps in the life of a mid-latitude cyclone?

1. Clash of two air masses 2. Wave develops along with a surface low pressure center 3. Development of cyclonic flow 4. Occlusion begins/Occluded Front Develops (Mature Stage)

types of lightning

1. Cloud to ground (CG) 2. Cloud to cloud (CC) 3. Cloud to air (CA) 4. Sheet lightning 5. Ball lightning 6. Heat lightning 7. Ribbon lightning

What are the two types of lightning?

1. Cloud-to-cloud lightning: strike occurs between two points in the cloud itself (often called sheet lightning) **80% of all lightning 2. Cloud -to-Ground lightning: electrical discharge occurs between cloud and Earth's surface **20% of all lightning

What are the three different Milankovitch Cycles? What are some characteristics of each?

1. Eccentricity: The change in the shape of Earth's orbit around the sun *Orbit changes between nearly circular to more elliptical and back. *One cycle of eccentricity spans about 100,000 years. *Perihelion receives about 20 - 30% more solar radiation than aphelion at maximum eccentricity. *Prime importance to glaciation 2. Obliquity: The change in the angle that the axis makes with the plane of Earth's orbit. *Axis tilt varies between 21.5° to 24.5°. *Today the tilt is 23.5° *Each cycle about 41,000 years. *Lower tilt primarily makes the seasons less extreme. *Smaller degree of tilt could promote the growth of ice sheets. 3. Precession: The wobbling of Earth's axis slowly as it orbits. *Each cycle is about 26,000 years. *At present, axis points towards North Star. In 12,000 years, axis will point towards the bright star Vega which will then become the North Star.

What are the different scales of winds? What are some examples of each?

1. Microscale - Turbulence, dust devils, gusts 2. Mesoscale - Thunderstorms, tornadoes, land - sea breezes 3. Macroscale - Westerlies, Tradewinds

What tools do we use for detecting, tracking and monitoring hurricanes? What are some characteristics of each?

1. Satellites: Single greatest advancement in tools used for observing tropical cyclones 2. Aircraft Reconnaissance: Airplanes that fly directly into hurricanes to take measurements. -Only give a "snapshot" of small parts of the storm 3. Radar: Used when Hurricane nears the coast and measures wind fields, rainfall intensity, and storm movement. Can't "see" farther than about 200 miles from the coast Is used to issue more short-term warnings (floods, tornadoes, high winds) 4. Data Buoys: Positioned in fixed locations all along the Gulf and Atlantic Coasts Only means of making nearly continuous direct measurements of surface conditions over oceans areas.

What are the different types of reflection?

1. Specular reflection: Reflection off a smooth surface *Like a smooth body of water or a mirror 2. Diffuse reflection: Reflection off an irregular surface *Like choppy water 3. Internal reflection: Light travels through a transparent material, and is then reflected off the back of that transparent material. *Like in a raindrop.

What are the various layers of the atmosphere? Characteristics of each?

1. Troposphere *Temperatures decreases with in increase in altitude *Where we live and where all weather occurs 2. Stratosphere *Temperature generally increases with height in this layer of the atmosphere *This is due to the ozone layer, which absorbs ultraviolet radiation from the sun which heats the stratosphere 3. Mesosphere *Temperatures again decrease with height *Top of mesosphere (mesopause) can reach -130°F 4. Thermosphere *Temperatures increase with height again, this time due to the absorption of very shortwave, high energy solar radiation by atoms of oxygen and nitrogen

How does the National Weather Service characterize a severe thunderstorm?

1. Winds in excess of 58 mph 2. Hail > 1 inch in diameter 3. Generate a tornado

average characteristics of a tornado

1. diameter: 100 yards 2. path length: 2-4 miles 3. lifespan: 5-10minutes 4. wind speeds: 80-300mph 5. forward speed: 30mph

Tornado life cycle

1. dust-whirl stage 2. organizing stage 3. mature stage 4. decaying stage

How do hurricanes decay?

1. move over colder ocean water that can not supply efficient tropical air 2. move onto land 3. reach a location where large scale flow is unfavorable

the forecasting process

1. observations 2. analysis 3. prediction 4. post-processing

types of forecasts

1. short term 2. medium term 3. long term

In a typical tornado the winds are usually not much more than _____ miles per hour.

100

If you see a lightning stroke and then, 15 seconds later, hear the thunder, the lightning is about ____ miles away.

3

long range forecast

5 - 10 days

A weather forecast is generally not that accurate after...

5 days

a long range forecast is a forecast that extends beyond about

8 days

What atmospheric levels do meteorologists often look at?

850-, 700-, 500-, 300-, and 200-millibar heights

What are they looking for levels of 850- and 700- mb?

850-, and 700- Can see warm- and cold-air advection 850- also used for determining rain vs. snow; daily max. temperatures at surface 700- also used for predicting movement of weather systems

The Coriolis force acts at a ____ degree angle to the wind​.

90

The Coriolis force acts at a _____ degree angle to the wind

90

comma clouds

A band of organized cumuliform clouds that looks like a comma on a satellite photograph.

gust front

A boundary that separates a cold downdraft of a thunderstorm from warm, humid surface air. On the surface its passage resembles that of a cold front.

dryline

A boundary that separates warm, dry air from warm, moist air. It usually represents a zone of instability along which thunderstorms form.

St. Elmo's Fire

A bright electric discharge that is projected from objects (usually pointed) when they are in a strong electric field, such as during a thunderstorm.

prognostic chart

A chart showing expected or forecasted conditions, such as pressure patterns, frontal positions, contour height patterns, and so on.

meteogram

A chart that shows how one or more weather variables has changed at a station over a given period of time or how the variables are likely to change with time.

What is a climograph? What variables are plotted?

A climograph Contains monthly average temperatures and precipitation values for one location

cut-off low

A cold upper-level low that has become displaced out of the basic westerly flow and lies to the south of this flow.

waterspout

A column of rotating wind over water that has characteristics of a dust devil and tornado.

Occluded front (occlusion)

A complex frontal system that ideally forms when a cold front overtakes a warm front. When the air behind the front is colder than the air ahead of it, the front is called a cold occlusion. When the air behind the front is milder than the air ahead of it, it is called a warm occlusion.

barotropic (atmosphere)

A condition in the atmosphere where surfaces of constant density parallel surfaces of constant pressure.

Overrunning

A condition that occurs when air moves up and over another layer of air

multicell thunderstorm

A convective storm system composed of a cluster of convective cells, each one in a different stage of its life cycle.

mesoscale convective vortex

A counterclockwise circulation, usually less than 240 km (150 mi) in diameter, about an area of low pressure that forms in the mid-levels of the atmosphere in association with a mesoscale convective system.

shelf cloud

A dense, arch-shaped, ominous-looking cloud that often forms along the leading edge of a thunderstorm's gust front, especially when stable air rises up and over cooler air at the surface. Also called an arcus cloud.

roll cloud

A dense, roll-shaped, elongated cloud that appears to slowly spin about a horizontal axis behind the leading edge of a thunderstorm's gust front.

statistical forecast

A forecast based on a mathematical/statistical examination of data that represents the past observed behavior of the forecasted weather element.

weather watch

A forecast indicating that atmospheric conditions are favorable for hazardous weather to occur over a particular region during a specified time period.

weather warning

A forecast indicating that hazardous weather is either imminent or actually occurring within the specified forecast area.

analog forecasting method

A forecast made by comparison of past large-scale synoptic weather patterns that resemble a given (usually current) situation in its essential characteristics.

probability forecast

A forecast of the probability of occurrence of one or more of a mutually exclusive set of weather conditions.

persistence forecast

A forecast that the future weather condition will be the same as the present condition.

weather type forecasting

A forecasting method where weather patterns are categorized into similar groups or types.

ensemble forecasting

A forecasting technique that entails running several forecast models (or different versions of a single model), each beginning with slightly different weather information. The forecaster's level of confidence is based on how well the models agree (or disagree) at the end of some specified time.

stationary front

A front that is nearly stationary with winds blowing almost parallel and from opposite directions on each side of the front.

Upper-air front

A front that is present aloft but usually does not extend down to the ground. Also called an upper front and an upper-tropospheric front.

What is the primary difference between a tornado and a funnel cloud?

A funnel cloud is a rotating cloud whose circulation has not reached the ground.

What is the primary difference between a tornado and a funnel cloud?

A funnel cloud is a tornado whose circulation has not reached the ground.

funnel cloud

A funnel-shaped cloud of condensed water, usually extending from the base of a cumuliform cloud. The rapidly rotating air of the funnel is not in contact with the ground; hence, it is not a tornado.

typhoon

A hurricane (tropical cyclone) that forms in the northwestern Pacific Ocean.

air mass

A large body of air that has similar horizontal temperature and moisture characteristics.

mesoscale convective complexes (MCC)

A large, organized convective weather system comprised of a number of individual thunderstorms. An MCC can span 1000 times more area than an individual ordinary cell thunderstorm. An MCC is a particular type of mesoscale convective system.

isallobars

A line of equal change in atmospheric pressure during a specified time interval.

bow echo

A line of thunderstorms on a radar screen that appears in the shape of a bow. Bow echoes are often associated with damaging straight-line winds and small tornadoes.

squall line

A line of thunderstorms that form along a cold front or out ahead of it.

sonic boom

A loud explosive-like sound caused by a shock wave emanating from an aircraft (or any object) traveling at or above the speed of sound.

secondary low

A low-pressure area (often an open wave) that forms near, or in association with, a main low-pressure area.

tropical depression

A mass of thunderstorms and clouds generally with a cyclonic wind circulation of between 20 and 34 knots (32 and 39 mi/hr).

Vorticity

A measure of the spin of a fluid, usually small air parcels. Absolute vorticity is the combined vorticity due to Earth's rotation (Earth's vorticity) and the vorticity due to the air's circulation relative to Earth. Relative vorticity is due to the curving of the air flow and wind shear.

tropical wave (easterly wave)

A migratory wavelike disturbance in the tropical easterlies. Tropical waves occasionally intensify into tropical cyclones. They are also called easterly waves.

Enhanced Fujita Scale (EF Scale)

A modification of the original Fujita Scale that describes tornado intensity by observing damage caused by the tornado.

Northeaster

A name given to a strong, steady wind from the northeast that is accompanied by rain and inclement weather. It often develops when a storm system moves northeastward along the coast of North America. Also called nor'easter.

Describe how Doppler radar measures the winds inside a severe thunderstorm.

A radar transmitter sends out microwave pulses that, are scattered back to the antenna when the microwave energy strikes an object. Precipitation particles are large enough to bounce microwaves back to the antenna. Doppler radar works on the principle that, as precipitation moves toward or away from the antenna, the returning radar pulse will change in frequency.

ball lighting

A rare form of lightning that may consist of a reddish, luminous ball of electricity or charged air.

tornado alley

A region in the Great Plains of the United States extending from Texas and Oklahoma northward into Kansas and Nebraska where tornadoes are most frequent. Same as tornado belt.

jet streak

A region of high wind speed that moves through the axis of a jet stream. Also called jet maximum.

Atmospheric River

A region of upper-level flow that transports large amounts of moisture, typically from the tropics and subtropics into the midlatitudes.

gustnadoes

A relatively weak tornado associated with a thunderstorm's outflow. It most often forms along the gust front.

omega high

A ridge in the middle or upper troposphere that has the shape of the Greek letter omega (Ω).

fulgrite

A rootlike tube (or several tubes) that forms when a lightning stroke fuses sand particles together.

Fujita scale

A scale developed by T. Theodore Fujita for classifying tornadoes according to the damage they cause and their rotational wind speed. (See also Enhanced Fujita Scale.)

Saffir-Simpson scale

A scale relating a hurricane's winds to the possible damage it is capable of inflicting.

Know and understand Monsoons

A seasonally driven change in wind direction, super high pressure over land causes winds to blow toward water.

tornado outbreak

A series of tornadoes that forms within a particular region—a region that may include several states. Often associated with widespread damage and destruction.

downburst

A severe localized downdraft that can be experienced beneath a severe thunderstorm. (Compare microburst and macroburst.)

supercell

A severe thunderstorm that consists primarily of a single rotating updraft. Its organized internal structure allows the storm to maintain itself for several hours. Supercell storms can produce large hail and dangerous tornadoes.

cold air damming

A shallow layer of cold air that is trapped between the Atlantic coast and the Appalachian Mountains.

overshooting top

A situation in a mature thunderstorm where rising air, associated with strong convection, penetrates into a stable layer (usually the stratosphere), forcing the upper part of the cloud to rise above its relatively flat anvil top.

eyewall replacement

A situation within a hurricane (tropical cyclone) where the storm's original eyewall dissipates and a new eyewall forms outward, farther away from the center of the storm.

shortwave

A small wave that moves around longwaves in the same direction as the air flow in the middle and upper troposphere. Shortwaves are also called shortwave troughs.

Alternating lines of blue and red on a surface weather chart indicate what?

A stationary front

What is a thunderstorm?

A storm containing lightning and thunder.

microburst

A strong localized downdraft (downburst) less than 4 km wide that occurs beneath thunderstorms. A strong downburst greater than 4 km across is called a macroburst.

heat burst

A sudden increase in surface air temperature often accompanied by extreme drying. A heat burst is associated with the downdraft of a thunderstorm, or a cluster of thunderstorms.

outflow boundary

A surface boundary formed by the horizontal spreading of cool air that originated inside a thunderstorm.

What is the relationship between surface high and low pressure centers and the flow aloft (convergence or divergence, troughs or ridges)?

A surface high will have a convergence in the flow aloft as well as a ridge. A surface low will divergence in the flow aloft as well as have a trough.

Frontal inversion

A temperature inversion encountered upon ascending through a sloping front, usually a warm front.

trade wind inversion

A temperature inversion frequently found in the subtropics over the eastern portions of the tropical oceans.

polar front theory

A theory developed by a group of Scandinavian meteorologists that explains the formation, development, and overall life history of cyclonic storms that form along the polar front.

How does the National Weather Service define a severe thunderstorm?

A thunderstorm having a least one of the following: -large hail with a diameter of at least one inch. -surface wind gusts of 50 knots (58 mph) or greater -or produces a tornado

nonsupercell tornadoes

A tornado that occurs with a cloud that is often in its growing stage, and one that does not contain a mid-level mesocyclone, or wall cloud. Landspouts and gustnadoes are examples of nonsupercell tornadoes.

How does a tornado watch differ from a tornado warning?

A tornado watch alerts the public that tornadoes may develop. A tornado warning means a tornado has already been spotted.

cold front

A transition zone where a cold air mass advances and replaces a warm air mass.

super typhoon

A tropical cyclone (typhoon) in the western Pacific that has sustained winds of 130 knots or greater.

What is an "Eddie" ?

A turbulent flow of wind

baroclinic instability

A type of instability arising from a meridional (north to south) temperature gradient, a strong vertical wind speed shear, temperature advection, and divergence in the flow aloft. Many mid-latitude cyclones develop as a result of this instability.

Know and understand Land and Sea Breezes

A type of thermal circulation, uneven heating rates of land vs water create mesoscale costal winds

mesocyclone

A vertical column of cyclonically rotating air within a supercell thunderstorm.

eyewall

A wall of dense thunderstorms that surrounds the eye of a hurricane.

Know and understand Santa Anna Winds

A warm and dry down slope wind in California that enhances wildfire risk.

frontal wave

A wavelike deformation along a front in the lower levels of the atmosphere. Those that develop into storms are termed unstable waves, while those that do not are called stable waves.

climatological forecast

A weather forecast, usually a month or more in the future, which is based upon the climate of a region rather than upon current weather conditions.

steady-state (trend) forecast

A weather prediction based on the past movement of surface weather systems. It assumes that the systems will move in the same direction and at approximately the same speed as they have been moving. Also called trend forecasting.

The term monsoon actually refers to what?

A wind system that seasonally changes direction

What first order classes are located across the U.S.?

A, B, C, and D

AWIPS

Acronym for Advanced Weather Interactive Processing System. New computerized system that integrates and processes data received at a weather forecasting office from NEXRAD, ASOS, and analysis and guidance products prepared by NMC.

Which way do winds flow around High pressure systems?

Air SINKS ABOVE a high pressure at the surface

Geostrophic Wind:

Air flow that is parallel to straight isobars or height contours

A(n) ____________________ is an extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given altitude

Air mass

How do we classify air masses?

Air masses are characterized by temperature and moisture content

Where do air masses originate? Where do they NOT originate?

Air masses originate in their source regions. They do not originate in the mid-latitudes

How does air pressure change with height? Increase? Decrease? At what rate?

Air pressure decreases exponentially with height.

The origin of cP and cA air masses that enter the United States is

Alaska and Canada

What are the two specific aneroid barometers and how does each work?

Altimeter - measures pressure but indicates altitude Barograph - records a trace of pressure

storm surge

An abnormal rise of the sea along a shore; primarily due to the winds of a storm, especially a hurricane.

NEXRAD

An acronym for Next Generation Weather Radar. The main component of NEXRAD is the WSR-88D Doppler radar.

Continental arctic (air mass)

An air mass characterized by extremely low temperatures and very dry air.

Maritime tropical (air mass)

An air mass characterized by high temperatures and high humidity.

Continental polar (air mass)

An air mass characterized by low temperatures and dry air. Not as cold as arctic air masses.

pattern recognition

An analogue method of forecasting where the forecaster uses prior weather events (or similar weather map conditions) to make a forecast.

Define Coriolis Force and how it works?

An apparent force created by the rotation of the earth. Deflects objects from a straight path. (It is only significant for fast moving objects)

wall cloud

An area of rotating clouds that extends beneath a supercell thunderstorm and from which a funnel cloud may appear. Also called a collar cloud and pedestal cloud.

Convergence

An atmospheric condition that exists when the winds cause a horizontal net inflow of air into a specified region.

divergence

An atmospheric condition that exists when the winds cause a horizontal net outflow of air from a specific region.

Define Ridge:

An elongated area of higher height on a constant pressure chart, indicating warm air.

Define Trough:

An elongated area of lower height on a constant pressure chart that indicates colder air.

wave cyclone

An extratropical cyclone that forms and moves along a front. The circulation of winds about the cyclone tends to produce a wavelike deformation on the front.

Define the "Three-Cell Model" and identify the concepts behind it

An idealized triple-cell model that transports heat and energy distribution across different parts of the hemisphere

stepped leader

An initial discharge of electrons that proceeds intermittently toward the ground in a series of steps in a cloud-to-ground lightning stroke.

Characteristics of Cold fronts:

Appears blue on a weather map, Blue triangles point in the direction the cold air is advancing, usually active weather along the cold front

Characteristics of Occluded fronts:

Appears purple on a weather map, where cold fronts and warm fronts run into each other, attached to strong low pressure systems (reason why fronts collide)

Characteristics of Stationary fronts:

Appears red and blue on a weather map, essentially no movement with this front, least active type of front, big difference in air masses (north and south of front)

Characteristics of Warm fronts:

Appears red on a weather map, Red ovals point in the direction the warm air is advancing, light rain along the warm front (sometimes)

Characteristics of Dryline fronts:

Appears yellow or brown on a weather map, seperates dry air from moist air, warm dry air (cT) moves over warm moist air (mT) causing it to be very unstable, severe weather

Why is it unwise to seek shelter under an isolated tree during a thunderstorm? If caught out in the open, what should you do?

As the electrons approach the ground, a region of positive charge moves up into the air through any conducting object, such as trees, buildings, and even humans. Because a positive charge tends to concentrate in upward projecting objects, such as trees, the upward return stroke that meets the stepped leader is most likely to originate from such objects. Thus it is unsafe to stand near a tree during an electrical storm.

What are the different characteristics of a hurricane?

At the very center of the storm is the Eye -precipitation ceases -winds subside Air moves upward forming large cumulonimbus clouds -the strong winds and heavy rains surrounding the center of circulation is called the Eye Wall.

Why do ordinary cell thunderstorms most frequently form in the afternoon?

Because air near the ground is most typically unstable in the afternoon.

What are the characteristics of the warm belt of the Conveyor Belt Model?

Carries warm, moist air from the Gulf of Mexico It slowly ascends as it converges with other air masses Cools adiabatically and produces wide band of clouds and precip During ascension, westerly winds eventually turn belt to turn east Main precipitation producer air stream in the midlatitude cyclone Warm air mass brings moisture Cold front actively lifts air

Explain how a cloud-to-ground lightning stroke develops.

Cloud-to-ground lightning begins within the cloud when the localized electric potential gradient exceeds 3 million volts per meter along a path perhaps 50 m long. This situation causes a discharge of electrons to rush toward the cloud base and then toward the ground in a series of steps. -Each discharge covers about 50 to 100 m, then stops for about 50-millionths of a second, then occurs again over another 50 m or so. -This stepped leader is very faint and usually invisible to the human eye. -As the tip of the stepped leader approaches the ground, the potential gradient (the voltage per meter) increases, and a current of positive charge starts upward from the ground (usually along elevated objects) to meet it. After they meet, large numbers of electrons flow to the ground and a much larger, more luminous return stroke several centimeters in diameter surges upward to the cloud along the path followed by the stepped leader.

How do we classify clouds? Given a description.

Clouds are classified by shape: Cirrus: high, white, thin, wispy Cumulus: globular cloud masses Stratus: sheets or layers of clouds that cover much of the sky And Height: High Clouds ("cirro-"): bases above 6,000 meters (20,000 ft) Middle Clouds ("alto-"): heights from 2000-6000 meters Low Clouds ("strato-"): heights below 2,000 meters

What are some characteristics of mid-latitude cyclones?

Cold and warm fronts extending from the center of low pressure Counterclockwise circulation exceed 1000 km across Travel west to east due to the Westerlies Last a few days to more than a week

What is a mesocyclone?

Column of cyclonically rotating air found within a supercell thunderstorm - often where tornadoes will form

analouge forecasts

Compare the current circulation patterns with a similar pattern of the past. The prediction is the same weather that occurred on the previous occasion will occur again. The weather types forecast is basically the same procedure.

Why is large hail more common in Kansas than in Florida?

Conditions over the Great Plains are more favorable for the development of severe thunderstorms.

What is a Mesoscale Convective Complex?

Consist of many t-storms organized in a cluster over a large area. The usually slow-moving complex can persist for 12 hours+. Usually develops as the result of a group of afternoon air-mass thunderstorms (MCC's are most common in the summer). When these storms begin to decay in the evening, the MCC starts to develop. As long as there is persistent strong low-level flow of very warm air, new storms will continually develop into a cluster. MCC's are self-propagating systems as gust fronts from existing cells lead to the formation of new powerful cells. New cells develop near the side of complex facing the inflow

What type weather maps and charts are most used to measure pressure?

Constant Pressure Charts (each map is divided into pressure levels or isobars)

Where are surface cyclones in relation to upper-level troughs and ridges, convergence and divergence?

Convergence at the surface is accompanied by divergence aloft and Divergence at the surface is accompanied by convergence aloft Surface cyclones generally form downstream (east) of an upper-level trough

Pacific Air

Cool, moist air that originates over the Pacific Ocean, moves eastward, then descends the Rocky Mountains and moves over the plains as dry, stable, relatively cool air.

How does Coriolis force increase or decrease?

Coriolis force increases from the equator and higher in the atmosphere. There is no Coriolis force at the equator

In the middle latitudes of the Northern Hemisphere, surface winds tend to blow ______ and ________ around an area of surface low pressure.

Counter clockwise, inward

What are the stages of an air mass thunderstorm?

Cumulus, Mature, and Dissapating

Know and understand Katabatic Winds

Descending winds, much stronger than mountain breezes, mainly happen during day time, not as prevalent on the mountains

heat lightning

Distant lightning that illuminates the sky but is too far away for its thunder to be heard.

How do tornadoes form?

During a storm, winds on the ground are weaker than winds aloft, creating a long rotation along the ground. A thunderstorm forms or advects over this rotation and the updrafts of the storm pulls this rotation vertically. Thanks to this vertical rotation a low pressure center forms and a tornado happens.

What happens during glacial periods to the proportion of 16O and 18O in the oceans?

During glacial periods, lighter 16O is caught in the ice while the heavier 18O is left in the oceans.

Explain both how and why there is a shift in tornado activity from early spring to mid summer?

During the winter, tornadoes are most likely to form over the southern Gulf states when the polar-front jet is above this region, and the contrast between warm and cold air masses is greatest. In spring, humid Gulf air surges northward; contrasting air masses and the jet stream also move northward and tornadoes become more prevalent from the southern Atlantic states westward into the southern Great Plains. In summer, the contrast between air masses lessens and the jet stream is normally near the Canadian border; hence, tornado activity tends to be concentrated from the northern plains eastward to New York State.

Fujita scale

EF-0: weak EF-1: moderate EF-2: significant EF-3: severe EF-4: devastating EF-5: incredible

In what part of the maritime world are hurricanes called typhoons?

East Asia

The name given to the current of warm water that replaces cold surface water along the coast of Peru and Ecuador during December is​

El Niño

The equation that demonstrates that the pressure, temperature, and density are related is

Equation of State

What atmospheric conditions lead to the formation of "fair weather" waterspouts?

Fair weather water spouts tend to form in much the same way that landspouts do -- when the air is conditionally unstable and cumulus clouds are developing. Some form with small thunderstorms, but most form with developing cumulus congestus clouds whose tops are frequently no higher than 3600m (12,000 ft.) and do not extend to the freezing level. Apparently, the warm, humid air near the water helps to create atmospheric instability, and the updraft beneath the resulting cloud helps initiate uplift of the surface air.

T/F. At any given time, only one jet stream can be found in the atmosphere

False

T/F. Chinook winds are a common phenomenon on the east side of the Appalachians

False

T/F. The central US is a very good air mass source region

False

T/F. The general circulation of the atmosphere represents the ACTUAL air flow around the world and not just an average

False

T/F. The pressure gradient force is non-existent at the equator

False

T/F. Weather in middle latitudes tends to move from east to west

False

What is the jet stream and what does it do?

Fast flowing, narrow air currents found in the atmosphere (just under the tropopause) They form at the boundaries of adjacent air masses with significant differences in temperature & pressure. The jet stream separates warmer air from colder air

A true cold front on a weather map is always

Followed by cooler air

numerical weather prediction

Forecasting the weather based upon the solutions of mathematical equations by high-speed computers.

What is the Low-Level Jet (LLJ) and what does it do/whats responsible for?

Form over central plains, close to surface, half the speed of upper level jets, advects moisture to overnight thunderstorm complexes (most common in the spring and summer and is responsible for early morning showers and thunderstorms)

What type of weather and source regions are associated with Maritime Polar (mP) air masses?

Forms over cold waters like the north Atlantic or Pacific Moves inland over the Pacific Moves northwest and northeast Causes major winter-time storms

What type of weather and source regions are associated with Continental Arctic (cA) air masses?

Forms over ice and snow covered regions of Alaska and Canada (usually winter) Brings very cold air south into the Central US Outbreaks of below zero Missouri and freezing weather in Florida. Air mass slowly warms as it heads south

What type of weather and source regions are associated with Continental Polar (cP) air masses?

Forms over ice and snow covered regions of Alaska and Canada (usually winter) Brings very cold air south into the Central US Outbreaks of below zero Missouri and freezing weather in Florida. Air mass slowly warms as it heads south

As the temperature contrast across a front lessens, the front will often weaken and dissipate. Such a condition is known as ____________________

Frontolysis

What is the difference between frontolysis and frontogenesis?

Frontolysis refers to a front weakening; frontogenesis refers to a front strengthening.

long-range forecast

Generally used to describe a weather forecast that extends beyond about 8.5 days into the future.

medium range-forecast

Generally used to describe a weather forecast that extends from about 3 to 8.5 days into the future.

short-range forecast

Generally used to describe a weather forecast that extends from about 6 hours to a few days into the future.

very short-range forecast

Generally used to describe a weather forecast that is made for up to a few hours (usually less than 6 hours) into the future.

​Suppose a west wind of 20 knots blows over a coastal region which is densely covered in shrubs. If this same wind moves out over the middle of a large calm lake, its speed and direction would probably be

Greater than 20 knots and more northwesterly

The large thermally driven convection cell that is driven by convective "hot" towers along the equator is the​

Hadley Cell

What Causes Air Pressure Differences?

Heating & Cooling of the air

What type of weather and source regions are associated with Continental Tropical (cT) air masses?

Hot and dry air masses originate over the deserts of Mexico. Air may be unstable, but lack of moisture ensures weather

Why do hurricanes form where they do?

Hurricanes are fueled by latent heat which they get from huge quantities of warm water and moisture. Coriolis Force is also needed to initiate rotational motion. => why hurricanes will never form on the ITCZ Hurricanes often start as disorganized arrays of clouds and thunderstorms, called tropical disturbances.

What type of data do we get from ice cores?

Ice cores provide a record of air temperatures and snowfall. Trapped air bubbles contain past atmospheric compositions. Cores also contain dust, ash, pollen, modern pollution.

In what region of the United States do dry line thunderstorms most frequently form? Why there?

In Western Texas, Kansas, and Oklahoma.

arctic front

In northern latitudes, the semi-permanent front that separates deep cold arctic air from the more shallow, less-cold polar air.

How do winds flow around a low pressure center?

In the Northern Hemisphere winds flow counter clockwise around a low pressure system. In the Southern Hemisphere winds flow clockwise around a low pressure system.

Where does the highest frequency of thunderstorms occur in the United States? Why there?

In the southeast states along the Gulf Coast with a maximum in Florida, because there is 1. plenty of available moisture, 2. unstable surface air, and 3. convergence.

Which of the following statements is the most plausible?

In winter cA source regions have lower temperatures than mP source regions

Suppose a parcel of air has a given temperature, pressure, and density. If the parcel's size remains the same while its temperature increases, then the air pressure inside the parcel will

Increase

Which state might experience fewer thunderstorms annually than Missouri?

Iowa

Wind blowing with sufficient force to rip the roof off buildings

Is uncommon

Why should you not open windows when a tornado is approaching?

It appears that opening windows during a tornado actually increases the pressure on the opposite wall and increases the chances that the building will collapse. Also, windows are usually shattered by flying debris and it is best to stay away from them.

Which statement best describes the North-Atlantic hurricane season?

It begins on 1 June and ends on 30 November with a peak in mid-September.

Which statement describes the polar front jet stream?​

It forms near the boundary called the polar front.

Which statement is true about a hurricane warning

It gives the percent chance of a hurricane's center passing within sixty-five miles of a community.

What are some characteristics of the jet stream? Wind speed? Time of year variations? Flow patterns?

Jet Stream = swift geostrophic airstreams in the upper troposhere that meander in relatively narrow belts *Occur at the top of the Troposhere *Near elevations of 7-12 km *Depths of 1-3 km *Widths of 100-500 km *And Speeds of 100-400 km per hour (60-240 mph) Polar Jet Stream: Winds speeds: *Summer: ~60 km/hr, located in S. Canada *Winter: ~125 km/hr, located in Central U.S. Zonal Flow: winds flow generally in west-east direction Meridional Flow: winds flow more north-south direction

Closer isobars means what? And creates what?

Larger pressure change over a shorter distance, creating a stronger wind

In which direction is light bent when traveling from one medium to another?

Light is bent towards the most dense medium

dry lightning

Lightning that occurs with thunderstorms that produce little, if any, appreciable precipitation that reaches the surface.

lake-effect snows

Localized snowstorms that form on the downwind side of a lake. Such storms are common in late fall and early winter near the Great Lakes as cold, dry air picks up moisture and warmth from the unfrozen bodies of water.

Mesoscale circulations have a(n) _______ duration than microscale circulations

Longer

On an upper-level chart cold air aloft is generally associated with ______ pressure

Low

wind speed maximum, which usually flows from the south or southwest, is known as a(n) ____________________ jet

Low-Level

How does a squall line differ from a Mesoscale Convection Complex (MCC)?

MCC's = large, circular convection systems. Squall lines are linear features.

__________ ________ air provides showers and precipitation to California and other coastal areas off the West Coast

Maritime Polar

In addition to carbon dioxide, what are some other atmospheric gases that are contributing to climate change? What are some characteristics of each?

Methane: *1.75 ppm of the atmosphere *about 20 times more effective than CO2 at absorbing infrared radiation emitted by the Earth *8 year residence time in the atmosphere Nitrous Oxide: *Primarily the result of agricultural activities (nitrogen fertilizers), but also the combustion of fossil fuels. *The lifetime of a N2O molecule is about 150 years Chlorofluorocarbons (CFCs): *Are not naturally present in the atmosphere *Contribute to the depletion of ozone *CFCs will remain in the atmosphere for decades, so even if CFC emissions were to stop immediately, the atmosphere would not be free of them for many years.

The unit of pressure most commonly found on a surface weather map is​

Millibars or Hectopascals

​A wind reported as 45° would be a wind blowing from the:

NE

Most cold fronts move:

NW to SE

Who can and cannot issue official weather watches and warnings?

National Weather Service (NWS) This is the main authority on issuing watches and warnings No other weather service, private or public can issue watches and warnings, only information and advice

What gases make up the composition of the atmosphere?

Nitrogen, Oxygen, Carbon Dioxide, Argon

NAM

North American Mesoscale model (numerical modeling)

What is the difference in temperature and moisture properties on either side of the jet stream?

North of the jet stream temperatures are colder, south temperatures are warmer

The polar front theory of a developing wave cyclone was conceived in

Norway

What are the various ways of forecasting?

Numerical Weather Prediction *Persistence Forecasting: If it is raining at a particular location, it might be reasonable to assume that is will still be raining in a few hours. *Climatological Forecasting: farmers (needing information on average first frosts) *Analog Method: based on the assumption that weather repeats itself *Trend Forecasting: A storm is moving to the NE at 35 mph. In two hours, it'll have gone 70 miles in the NE direction

dry slot

On a satellite image the dry slot represents the relatively clear region (or clear wedge) that appears just to the west of the tail of a comma cloud of a mid-latitude cyclonic storm.

Describe one process by which thunderstorms become electrified.

One theory proposes that clouds become electrified as grapple and hail fall through a region of supercooled droplets and ice crystals. As liquid droplets collide with a hailstone, they freeze on contact and release latent heat. This process keeps the surface of the hailstone warmer than that of the surrounding ice crystals. When the warmer hailstone comes in contact with a colder ice crystal, an important phenomenon occurs: there is a net transfer of positive ions from the warmer object to the colder object. Hence, the hailstone becomes negatively charged and the ice crystal positively charged, as the positive ions are incorporated into the ice.

Where do certain positive and negative charges lie within a cloud?

One theory suggests that charge separation occurs during formation of ice pellets. Droplets begin to freeze, positively charged ions concentrate in the upper, colder portion of the cloud and negative ions in the warmer regions. Since the lower portion of the cloud is negatively charged, a positive charge is induced on the ground below it.

What are the characteristics of the dry belt of the Conveyor Belt Model?

Originates in the upper troposphere Cold and dry Splits as it enters the cyclone - Clear, cool conditions behind the cold front - Creates the dry slot of the comma shaped cyclone

Where do thunderstorms occur most (when considering both air mass type and location in the U.S.)?

Over Florida due to Convergence of air, warm air, and moisture content

Where do hurricanes form?

Over tropical or subtropical oceans with the exception of the South Atlantic and and Eastern South Pacific

What is ozone? Characteristics of ozone?

Ozone is concentrated well above the surface of the Earth in a layer called the stratosphere Ozone absorbes harmful UV radiation and keeps it from coming to earth's surface

What is the PBL?

Planetary Boundary Layer, atmospheric layer or friction ;ayer that influences scales

From LARGEST to SMALLEST, what is the correct order of the Scales of Motion?

Planetary, Synoptic, Mesoscale, Microscale

What are positive and negative feedback mechanisms in regards to climate change?

Positive Feedback Mechanism *Warmer Temperatures > more ice melts > lower albedo > more absorption of incoming radiation > warmer temperatures Negative Feedback Mechanism *Warmer Temperatures > increased evaporation > more cloud cover > reduced incoming solar radiation > cooler temperatures

trend forecasts

Predict that circulation features (high and lows) will continue to move in the same direction and at the same speed in the future as in the past.

What forces act on moving air (wind)? Which of those forces generates wind movement?

Pressure Gradient Force Coriolis Force Friction *Pressure Gradient Force generates wind movement

Small changes in elevation produce large pressure changes, so....

Pressure readings from different elevations must be reduced to sea level to be able to compare them

The only indication on the station model of past weather conditions is the

Pressure tendency

Supercell thunderstorms that produce tornadoes form in a region of strong vertical wind shear. Explain how the wind changes in speed and direction to produce this shear.

Rapidly increasing wind speed with height provides vertical speed wind shear and the changing wind direction with height -- from southerly at low levels to westerly at high levels -- provides wind direction shear, which induces the updrafts inside the storms to rotate.

What is a squall line?

Relatively narrow band of thunderstorms that develops in the warm sector of a midlatitude cyclone (mainly fall and spring). Some of the storms may be severe. Usually 100 to 300 km (60 to 180 miles) in advance of the cold front. Band of cumulonimbus development may stretch for 500 km (300 miles) or more. An average squall line can last for 10 hours or more

landspout

Relatively weak nonsupercell tornado that originates with a cumiliform cloud in its growth stage and with a cloud that does not contain a mid-level mesocyclone. Its spin originates near the surface. Landspouts often look like waterspouts over land.

What are troughs and ridges? What is zonal vs. meridional flow?

Ridge = an elongate region of high atmospheric pressure Trough = an elongate region of low atmospheric pressure The jet stream flows in two ways: 1. Zonal Flow: winds flow generally in west-east direction 2. Meridional Flow: winds flow more north-south direction

Upwelling is

Rising of cold water from below

The Coriolis Force varies with:

Rotation of Earth Latitude Speed of Object

There are regions where pressure systems appear to persist throughout the year. These systems are referred to as ____________________ because they move only slightly during the course of a year

Semi-permanent highs and lows

atmospheric models

Simulation of the atmosphere's behavior by mathematical equations or by physical models.

Why do pressure readings from different elevations need to be brought to sea-level to compare?

Small changes in elevation produce large pressure changes

suction vortices

Small, rapidly rotating whirls perhaps 10 m in diameter that are found within large tornadoes.

If you live in the Northern Hemisphere and a region of surface low pressure is directly west of you, the surface wind direction at your home would probably be ________ or _________

South or Southeast

The magnitude of the Coriolis force varies with ____ and ____

Speed, Latitude

Know and understand Dust Devils

Spinning vortices commonly seen on hot days in dry areas (deserts)

Describe the stages of development of an ordinary cell (air mass) thunderstorm?

Stage 1: cumulus stage, or growth stage. -As a parcel of humid air rises, it cools and condenses into a single cumulus cloud or cluster of clouds. -During this stage there normally is insufficient time for precipitation to form, and the updrafts keep water droplets and ice crystals suspended within the cloud. -No lightning or thunder during this stage. Stage 2: Mature Stage -Appearance of the downdraft marks the beginning of the mature thunderstorm. The downdraft and updraft within the mature thunderstorm constitute a cell. -most intense during mature stage. -in mature stage, the storm begins to dissipate in about 15 to 30 minutes. Stage 3: Dissipating Stage -Dissipating stage occurs when updraft weakens as the gust moves away from the storm and no longer enhances the updrafts.

What is storm surge? Where and how is storm surge the most intense?

Storm surge is a dome of water 40-50 miles wide that sweeps across the coast near the point where the eye makes landfall; the height of the water above normal tide level. In Northern Hemisphere, Storm Surge is always most intense on the right side of the eye, where winds are blowing towards the shore.

lee-side low

Storm systems (extratropical cyclones) that form on the downwind (lee) side of a mountain chain. In the United States lee-side lows frequently form on the eastern side of the Rockies and Sierra Nevada mountains.

derecho

Strong, damaging, straight-line winds associated with a cluster of severe thunderstorms that most often form in the evening or at night.

When is the Low Level Jet stream strongest and weakest?

Strongest at night and weakest in the mid-morning

Where is the Coriolis Force most strong and most weak?

Strongest at the poles, weakest at the equator

What is the relationship between sunspots and temperatures?

Sunspots are huge magnetic storms that extend from the Sun's surface deep into the interior. Studies have identified prolonged periods when sunspots are sparse, colder conditions prevailed in Europe and North America, and vice versa

What makes supercell thunderstorms different from severe thunderstorms?

Supercells consist of a single, very powerful cell extending to heights of 65,000 ft and can persist for many hours These contain rotation which can cause very violent tornadoes.

Supercooled water droplets will _____ on contact with a falling ice crystal?

Supercooled water droplets will FREEZE on contact with a falling ice crystal

How do volcanic eruptions influence global temperatures?

Suspended material in the air blocks incoming solar radiation, which in turn lowers temperatures in the troposphere

If you are in a single-story home (without a basement) during a tornado warning, what should you do?

Take cover in a small room, such as a bathroom, closet, or interior hallway near the middle of the building.

Ocean atmosphere interactions, where warm or cold surface ocean temperatures can influence precipitation patterns in a distant part of the world are called ______

Teleconnections

A sea or land breeze is caused by

Temperature differences

Describe the different ways that temperature can vary?

Temperature of the atmosphere can vary by sun angle and the length of daylight Differential heating of land and water Ocean currents Altitude Geographic position Cloud cover and albedo

How has Doppler radar helped in the prediction of severe weather?

The NEXRAD network of Doppler radar units deployed at selected weather stations within the continental United States take in data, display it on monitors, and run computer programs called algorithms, which, in conjunction with other meteorological data, detect severe weather phenomena, such as storm cells, hail, mesocyclones, and tornadoes. The algorithms provide a great deal of information to the forecasters that allows them to make better decisions as to which thunderstorms are most likely to produce severe weather and possible flash flooding. In addition, they give advanced and improved warning of an approaching tornado.

Give some average statistics about tornado size, winds, and direction of movement.

The diameter of most tornados is between 100 and 600 m (about 300 to 2000 ft), although some are just a few meters wide and others have diameters exceeding 1600 m (1 mi). They tend to move from the southwest toward the northeast at speeds usually between 20 and 40 knots.

Conditionally unstable atmosphere occurs when...

The environmental Lapse Rate falls BETWEEN the Dry and Moist Adiabatic Rates - Can become unstable by: Rising air becoming saturated

Why is the polar jet stream strongest in the winter and weakest in the summer (NH)?

The general circulation of the atmosphere shifts south toward the equator, drawing in colder air from the arctic into the US

tropical cyclone

The general term for storms (cyclones) that form over warm tropical oceans.

(a) How do gust fronts form? (b) What type of weather does a gust front bring when it passes?

The gust front = leading edge of cold air originating inside a thunderstorm. During its passage, the wind shifts and becomes strong and gusty, with speeds occasionally exceeding 55 knots. Temperatures drop sharply and, in the cold, heavy air of the downdraft, the surface pressure often rises -- sometimes several millibars.

Define Pressure Gradient Force (PGF) and how it works?

The horizontal difference in pressure, oriented from high pressure toward lower pressure

cumulus stage

The initial stage in the development of an ordinary cell thunderstorm in which rising, warm, humid air develops into a cumulus cloud.

What is a gust front? And how is it formed?

The leading edge of this outflowing downdraft acts like a wedge, forcing warm, moist surface air into the thunderstorm. Outflowing cool air acts as a "mini cold front" as it advances into the warmer surrounding air.

return stroke

The luminous lightning stroke that propagates upward from Earth to the base of a cloud.

How have average global temperatures changed in the last century?

The mean annual temperature has had a rising trend over the last century. *Total warming in the last century is 0.8C or 1.4F

What are the only two atmospheric variables that the Climate Prediction Center makes a forecast for longer than a week out?

The only variables predicted for the long-term: precipitation (drier or wetter) and temperature (above or below normal conditions)

Where is the effect of the Coriolis force the greatest?

The poles

What does the presence of water vapor do to the atmosphere?

The presence of water vapor allows for heat transfer from warm, moist regions to cooler, dry regions. This is what drives weather. H2O vapor is the source of all clouds and precipitation, but it also absorbs heat given off by Earth as well as some solar energy.

Define station pressure:

The pressure reading after correcting for temperature, gravity, and instrument error

chaos

The property describing a system that exhibits erratic behavior in that very small changes in the initial state of the system rapidly lead to large and apparently unpredictable changes sometime in the future.

How do clouds form? What is needed to generate the formation of clouds?

The purpose of adiabatic cooling and mechanical forcing is to raise parcels so that the dew point of the parcel can be reached - At that point, condensation will begin For condensation to occur two things are required: saturation of the air (100% RH) and a surface on which to condense. *Called Cloud Condensation Nuclei **Ex: microscopic dust, smoke, and salt particles If no surface is available, a RH will in excess of 100% (supersaturation) is needed to produce cloud droplets.

warm sector

The region of warm air within a wave cyclone that lies between a retreating warm front and an advancing cold front.

Earth's vorticity

The rotation (spin) of an object about its vertical axis brought on by the rotation of Earth on its axis. Earth's vorticity is a maximum at the poles and zero at the equator.

If you are in a single-story home (without a basement) during a tornado warning, what should you do?

The safest place is usually in a small room such as a bathroom, closet or interior hallway near the middle of the building.

hook echo

The shape of an echo on a Doppler radar screen that indicates the possible presence of a tornado.

baroclinic (atmosphere)

The state of the atmosphere where surfaces of constant pressure intersect surfaces of constant density. On an isobaric chart, isotherms cross the contour lines, and temperature advection exists.

What type of radiation does the sun and earth each give off?

The sun gives off short-wave radiation. The Earth gives off long-wave radiation.

Give a possible explanation for the generation of a pre-frontal squall-line thunderstorm.

The surging nature of the main cold front itself, or developing cumulus clouds along the front, may cause the air aloft to develop into waves (called gravity waves), much like the waves that form downwind of a mountain chain. -Out ahead of the cold front, the rising motion of the wave may be the trigger that initiates the development of cumulus clouds and a pre-frontal squall line.

cold advection

The transport of cold air by the wind from a region of lower temperatures to a region of higher temperatures.

Vorticity advection

The transport of vorticity by the wind. Positive vorticity advection occurs when the wind blows from high vorticity toward low vorticity, resulting in an increase in vorticity over time at a location. Negative vorticity advection occurs when the wind blows from low vorticity toward high vorticity, resulting in a decrease in vorticity over time at a location.

warm advection

The transport of warm air by the wind from a region of higher temperatures to a region of lower temperatures.

How does negative cloud-to-ground lightning differ from positive cloud-to-ground lightning?

The typical cloud-to-ground lightning flash is called negative cloud-to-ground lightning, because the stroke carries negative charges from the cloud to the ground. About 90 percent of all cloud-to-ground lightning is negative. However, when the base of the cloud is positively charged and the ground negatively charged, a positive cloud-to-ground lightning flash may result. Positive lightning, most common with severe thunderstorms, has the potential to cause more damage because it generates a much higher current level and its flash lasts for a longer duration than negative lightning.

How do supercell thunderstorms differ from ordinary cell (air mass) thunderstorms?

The updraft in a super cell storm is longer-lasting and rotates.

How do we name hurricanes?

There are 6- pre-arranged lists that rotate every 6 years. They go in alphabetical order and each storm is assigned a name.

What does a probability forecast that calls for a "40% chance of rain" mean?

There is a 40% chance that any random place in the forecast area will receive measurable rain

When thunderstorms are training, what are they doing?

They keep passing over the same area, like railroad cars, one after the other, passing over the railroad tracks.

How is thunder produced?

Thunder is the sound that results from the rapidly expanding heated air along the channel of the lightning stroke.

What is frontogenesis?

To strengthen a front, increase the temperature difference across the front

What are some characteristics of tornadoes?

Tornadoes can form any time of year and any time of day, but they're much more common in the early summer months (peak season being around April) and afternoon-late night hours. Tornadic activity is found sparingly throughout the world, with the United States having the most They generally form ahead of a cold front and move in a southwest northeast track, but they can move in any direction

supercell tornadoes

Tornadoes that occur within supercell thunderstorms that contain well-developed, mid-level mesocyclones.

T/F. A good air mass source region is generally flat and of uniform composition with light surface winds

True

T/F. Coastal areas can have strong waves on a clear, non-stormy day

True

T/F. Jet streams sometimes split into two branches

True

T/F. Pilots prefer to fly in the core of a jet stream (especially flying from west to east)

True

​T/F. In middle latitudes, surface pressure changes are primarily the result of large high- and low-pressure areas that move toward or away from a region

True

Explain why ordinary cell thunderstorms tend to dissipate much sooner than multi cell storms.

Unlike the ordinary storm (ordinary storm weakens once it enters the dissipation stage), the supercell storm is an enormous rotating thunderstorm whose updrafts and downdrafts are sufficiently structured so that the storm is able to maintain itself as a single entity for hours on end. -Storms of this size are capable of producing updrafts that can exceed 90 knots, hail the size of a grapefruit, damaging surface winds, and large, long-lasting tornados. -Normally, precip. does not form in the region of the strong updraft. -If precip does form, it may be swept laterally out of the region by the rapidly rotating air.

What are they looking for levels of 500-mb?

Used for estimating the movement of cyclonic storms which flow in the direction of the flow at this height, but at roughly ¼-1/2 the speed

What are they looking for levels of 300- and 200-mb?

Used for identifying the location of the jet stream (300-mb map in winter, 200-mb map in summer)

How (and how often) do we get vertical profiles of atmospheric conditions?

Using radiosondes, which are released twice a day (00z and 12z) they are attached to weather balloons.

You observe the wind shift from easterly to southerly. This shift in wind is accompanied by a sudden rise in both the air temperature and dew-point temperature. This means a(n) _____ front passed

Warm

What are the 'belts' of the Conveyor Belt Model?

Warm conveyor belt Cold Conveyor belt Dry Conveyor belt

Chinook winds are

Warm, downslope winds

What atmospheric conditions are necessary for the development of ordinary cell (air mass) thunderstorms?

Warm, humid air masses away from significant weather fronts.

What type of weather and source regions are associated with Maritime Tropical (mT) air masses?

Warm, moist air from the sub-tropical Pacific, the Gulf of Mexico, and/or the south Atlantic moves inland. In California (winter), the "Pineapple Express" brings heavy rain and mudslides. Humid air is a fuel source for summer and winter storms in the Midwest

Release of Latent heat from a cloud causes the air at the top of a mountain to be ____....

Warmer than it would be otherwise

What are the basics elements of weather and climate?

Weather = State of the atmosphere at any given time or place What we are experiencing now is weather Constantly changing Climate = General description of the weather at a certain time and place, including variations and extremes of weather. A time period of 30 years is most often used to determine the climate of a region

What is the difference between weather and climate?

Weather is what is happening right now. Climate is long term.

The majority of the United States lies within this wind belt

Westerlies

How do derechoes form?

When damage associated with straight-line winds extends for several hundred kilometers along the path of a squall line, the storm is called a derecho.

Where are the Mid-Latitudes and why is the weather so "changeable?"

Where we live,

What does Wind Vane measure?

Wind (direction only), spins on a post until arrow points into the wind

Wet & Dry Monsoons -Why does this happen?) And where do Monsoons happen?

Winter monsoon means dry season and winds blow from land to sea. Summer monsoon means wet season and wind blows from sea to land

How do we rank the intensities of tornadoes?

With the Enhanced Fujita Scale (EF-Scale) This goes from 0-5 with 0 being the weakest and 5 being the strongest. This is based on the wind speed in sustained 3 second gusts

How do we rank the intensities of a hurricane?

With the Saffir-Simpson Scale Category based on observed conditions of PRESSURE and WIND SPEEDS Can change through time Viewed as estimates of the amount of damage it would cause if it made landfall right now Category 1 is least severe and 5 is most

Which is considered a major hurricane

a category 3 storm or higher

station model

a cluster of current weather data for one particular weather reporting site - top left # = temp - bottom left # = dewpoint - right # - pressure

On a weather map, the transition zone between two air masses with sharply contrasting properties is marked by

a front

What does "frontogenesis" mean when used in connection with a weather map?

a front is regenerating or strengthening

mesocyclone

a large rotating vortex inside a supercell thunderstorm that will sometimes produce tornadoes

stream lines

a line that shows the wind flow pattern

what is a tornado

a rapidly rotating column of air whose rotation reaches the ground

Which of the following phrases best describes a tornado?

a rapidly rotating column of air with extreme horizontal winds

Which best defines a thunderstorm cell

a single individual thunderstorm consisting of an updraft and downdraft

How is lightning formed?

a sudden flash of light generated by the flow of electrons between oppositely charged parts of a cumulonimbus cloud or between the clouds and the ground

What is an analysis?

a surface or upper-level chart that interprets the present weather patterns

What is the definition of a "weather front?"

a transition zone between air of different densities or a boundary between air masses with different characteristic

How does Mercury work when measuring pressure?

a tube of mercury rises and falls with pressure changes

What is an "eddie"?

a turbulent flow of wind

In a hurricane, what does the eye wall represent?

a zone of intense thunderstorms around the center

When the mass of an object is constant, the force acting upon that object is directly related to the ___________

acceleration that is produced

Where are supercell thunderstorms most likely found?

ahead of a cold front in the warmer air

everything is straightforward in a station model except for

air pressure

Define Sea-level Pressure Chart:

all station pressures are reduced to sea level and plotted on the same map

Where do hurricanes not form

along the equator

On which of the following criteria does the Enhanced Fujita (EF) scale classify tornado intensity?

amount of damage to structures

What is a distinguishing feature of a hurricane

an eyewall

Hadley Cell - what is it and where is it located?

an idealized single-cell model that transports heat from the equator to the pole, "convection cell", start at the equator with warm rising air surface winds move from the north to south and are turned right by Coriolis: Northeast Trade Winds

a comma cloud is

an organized band of clouds that looks like a comma on a satellite photograph

A forecast of "an extended period of dry weather" would be made for a region beneath ________________.

an upper level ridge

pattern matching =

analogue forecasting

an "okay" method of forecasting

analogue forecasting - patterns are repeatable but exact evolution is not always the same

_______ momentum is defined as the product of the mass (m) times the velocity (v) times the radial distance (r).​

angular

What is not a name for a large cyclonic storm system that forms in the middle latitudes?

anticyclone

Low Pressure: What does it mean? What type of weather do you get?

associated with cooler air and stronger winds, unsettled weather (rising air motions) (winds blow "in" toward the center of low pressure

High Pressure: What does it mean? What type of weather do you get?

associated with warmer air and weaker winds, fair and calm weather (sinking air motions) (winds blow "out" away from center of high pressure)

trend method

assumes that the speed and directions of weather systems will NOT change

Which below is not correct concerning an occluded front?

at the surface, it is always followed by colder air true: - if is often associated with a broad band of precipitation -it marks a zone of shifting wind - it is colored purple on a surface weather map

What is a wind that changes direction in a counterclockwise sense with increasing height called?

backing wind

On an upper-level chart where the isotherms cross the isobars (or contours) and temperature advection occurs, the atmosphere is _____________.

baroclinic

climatological forecasts

based on the fact that climate changes only slightly over long periods (decades) and that weather events in the future will occur with the same frequency as in the past

for a forecast to show skill it must

be better than one base on persistence or climatology

why do ordinary cell thunderstorms most frequently form in the afternoon?

because air near the ground is typically most unstable in the afternoon

Why are you generally safe inside an automobile during a lighting storm?

because the metal car body will carry the lightning current around the passengers inside

What is the main reason hurricanes don't develop over the South Atlantic Ocean adjacent to South America?

because the surface water temps are too cold

Very short-range forecasts often utilize which forecast method(s)?

both steady-state (trend method) and pattern recognition method

What is a radar signature that appears as a squall line pushed forward in just one particular spot by strong winds?

bow echo

Convective Available Potential Energy (CAPE) is a measure of the

buoyancy of air parcels in the environment

Which of the following air masses is associated with record-breaking low temperatures in twenty-four states in the United States?

cA

Record breaking low temperatures are associated with which air mass?

cP

What type of air mass is responsible for lake-effect snows in the Great Lakes region?

cP

What type of air mass would be responsible for refreshing cool, dry breezes after a long summer hot spell in the Central Plains?​

cP

Which air masses are formed in regions where long, clear nights allow for strong radiational cooling of the suface?

cP and cA

Which air mass would show the most dramatic change in both temperature and moisture content as it moves over a large body of very warm water?

cP in winter

What type of air mass would be responsible for hot, dry summer weather in southern Arizona?

cT

A warm front with precipitation approaches your location in winter. Which sequence of clouds would you most likely expect to observe?

cirrus, cirrostratus, altostratus, and nimbostratus

Suppose that where you live, the middle of January is typically several degrees warmer than the rest of the month. Which type of forecast would you make if you forecast this "January thaw" for the middle of next January?

climatological forecasting

"not a bad guide but it could be better!"

climatology

High pressure flow is:

clockwise

One would expect a cP air mass to be:

cold and dry

Squall lines most often form ahead of a ________.

cold front

Squall lines most often form to the east and south of which type of front?

cold front

What type of weather front would be responsible for the following weather forecast? "Increasing cloudiness and warm today with the possibility of showers by this evening. Turning much colder tonight. Winds southwesterly becoming gusty and shifting to northwesterly by tonight."

cold front

What type of weather front would likely be responsible for the following weather forecast? "Increasing cloudiness and warm today with the possibility of showers by this evening. Turning much colder tonight. Winds southwesterly becoming gusty and shifting to northwesterly by tonight."

cold front

Thunderstorms are most likely to form along which type of front?

cold fronts

What type of weather front would be responsible for the following weather forecast? "Light rain and cold today with temperatures just above freezing. Southeasterly winds shifting to westerly tonight. Turning colder with rain becoming mixed with snow, then changing to snow."

cold type occluded front

What is an Alberta Clipper and where does it originate?

cold, wind cyclonic storm that forms on the leeward side of the Canadian Rockies in the province of Alberta bring significantly cooler temperatures travel very quickly very dry air, light snow

What is weather analysis?

collecting, transmitting, and compiling billions of pieces of observational data to understand current conditions.

Santa Ana winds warm by ____________________ as they flow down an elevated desert plateau.

compression or compressional heating

the piling up of air above a region is called

convergence

Developing low-pressure areas generally have __________ air near the surface and __________ air aloft.

converging, diverging

_________ regions have low heights on pressure charts

cooler

What is Model Output Statistics?

corrects for errors the model tends to make consistently *MOS forecasts form the basis from which meteorologists make their forecasts.

In the middle latitudes of the Northern Hemisphere, surface winds tend to blow_________ and _________ around an area of surface low pressure.

counter-clockwise; inward

sound of thunder when its close

crank and a bang

the development or strengthening of a middle latitude storm system is called

cyclogenesis

What is a panhandle hook and where does it originate?

cyclones that form near the panhandle of Oklahoma and "hook" up northward as traveling east

If the outflow of air around a surface high-pressure area is greater than the convergence of air aloft, what will the surface pressure in the center of the high do?

decrease

Atmospheric air pressure always _________ with height.

decreases

what is a long-lived, straight-line wind produced by strong downbursts from an intense thunderstorm

derecho

When a storm system intensifies or deepens (that is, its central pressure decreases), what happens at upper levels?

divergence exceeds low level convergence

For cyclogenesis to occur along a frontal wave, the winds aloft directly above the wave should be

diverging

numerical models work by

dividing the atmosphere into 3D boxes called grids - the point in the middle is called the grid point

Before the passage of a cold front the pressure normally _______, and after the passage of a cold front the pressure normally _______.

drops, rises

Near the Sub-Tropical Highs:

dry, hot, deserts

On a surface weather map that shows an open wave cyclone, where can the warm sector be observed?

east of an advancing cold front

In which direction do tropical cyclones generally tend to move?

east to west

Which forecasting technique produces several versions of a forecast model, each beginning with slightly different weather information to reflect errors in the measurements?

ensemble forecasting

The equation that demonstrates that pressure temperature and density are related is:

equation of state

A tropical cyclone refers to

events that are classified as tropical storms or hurricanes

During a major El Niño event,​

extensive ocean warming occurs over the tropical Pacific.

a microburst produces

extremely strong straight-line winds

High pressure means:

fair weather

Chinook winds are a common phenomenon on the east side of the Appalachians.

false

T or F: Cold fronts are colored purple on a weather map.

false

T or F: The "average" speed of a cold front is about half that of an "average" warm front.

false

T or F: The general circulation of the atmosphere represents the actual air flow around the world and not just an average.

false

T or F: The pressure gradient force is non-existent at the equator.

false

When comparing an "average" cold front to an "average" warm front, which statement is false?

false:Generally, precipitation covers a much broader area with a cold front. true: - cold fronts move faster than warm fronts -cold fronts have steeper slopes -esp in winter, cumuliform clouds are often associated with cold fronts

When using the Coriolis Force, the __________ the speed of an object, the greater the deflection of the object.

faster

Atmospheric shortwaves usually move ________ than longwaves, and ________ when they move through a longwave ridge.

faster, weaken

2. analysis

figure out what storm systems are out there - cold/warm fronts, highs/lows

analogue forecasting

find a date in the past where the weather map looks exactly as it does now (aka pattern matching)

What causes most of the destruction caused by a hurricane

flooding

Which weather event kills more people annually than any other

flooding

A true cold front on a weather map is always

followed by cooler air

analogue forecasting relies heavily on

forecaster experience

If a building is not available, where is the safest place to go to during a thunderstorm?

forest

Winds at Earth's surface are much slower than at higher elevations and altitudes because of _________

friction (in turn this also reduces the Coriolis Force)

long term forecast

have you ever seen a 10 day forecast?

a weather warning indicates that

hazardous weather is either imminent or occurring within the forecast area.

In the polar front theory of a developing wave cyclone, energy for the storm is usually derived from all of the following except

heat energy stored in the ground is derived from: - rising of warm air and the sinking of cold air - latent heat of condensation - an increase in surface winds

Wind speed increases with ______ because:

height; the farther you are from the surface, the farther you are from the source of frictional slowing

Warm air aloft is associated with _________ atmospheric pressure.

high

Which of the following is MOST likely associated with fair weather?

high pressure area

Which of the following statements best describes a blocking high?

high pressure system the persists in the same location for many days

What would you not expect to observe as the eye of a hurricane passed directly over your area?

high winds would expect: increase in surface temperature, very low surface pressure reading, little to no precipitation

If Earth did not rotate, the wind would blow directly from regions of ________ pressure toward regions of ___________ pressure.

high; low

What does Wind Profiler measure?

how wind changes with height, its a vertical pointing radar

What does a hurricane watch indicate?

hurricane conditions are possible in your area for the next 24-48 hours

decoding air pressure on station model plots

if the pressure number starts with a 0 or a 1, place a 10 in front of the number and move the decimal place to the left one space - 145 =1014.5 - 094 = 1009.4

Where are the strongest winds in a hurricane found

in the eye wall

Which pressure unit is most commonly used in aviation?​

inches of mercury

If the flow of air into a surface low-pressure area is greater than the divergence of air aloft, what will the surface pressure in the center of the low do?

increase

What are lines connecting points of equal pressure change on a weather map?

isallobars

Lines of equal pressure on a weather map are called:

isobars

Why is the "Three-Cell Model" is somewhat idealized?

it accounts for earth's rotation but ignores land/water contrasts and migration of the sun's direct rays.

if rotation drops to the surface,

it creates a tornado

Which of the following is not correct concerning a warm front?

it has warm air ahead in advance of it true: - it is colored red on a weather map - in winter it is usually associated with stratiform clouds - it normally moves more slowly than a cold front

Which statement is false concerning a cold front?

it is colored purple on a weather map true: - it marks the position of a trough of low pressure - it marks a zone of shifting winds - it has cold air behind it

What is El Niño and how does it differ from La Niña?

its a warm current of water, only lasts a few weeks to a month or so. (el nino forms in low pressure over eastern pacific, while el nina forms in high pressure over eastern pacific) (el nino forms in high pressure over western pacific, while el nina forms in low pressure over western pacific)

medium term forecast

its ok, but many things can change!

A condition where the central and eastern tropical Pacific Ocean turns cooler than normal is called​:

la nina

The greatest contrast in both temperature and moisture will occur along the boundary separating which air masses?

mT and cP

What is the classification for a moist, tropical air mass that is warmer than the surface over which it is moving?

mTw

Modern computer forecasting models have increasingly smaller grid spacing. This presents what problem?

many more computations are needed

The smallest scale of atmospheric motion is the:

microscale

Sea breezes begin by ______________, and often produce _____________>

mid-late morning; thunderstorms

What is the Mesoscale?

middle scale, includes fronts and thunderstorms, from a few km to 500 km, lasts hours to a few days

MOS

model output statistics - tons of weather info

NGM

nested grid model (numerical modeling)

would a forecast calling for a 20% chance of rain be high enough for you to cancel your plans for a picnic?

no because widely scattered showers are expected

Which weather forecast for the immediate future employs the trend method?

nowcasting

numerical modeling

numerical equations exist to calculate the future state of certain variables

The forecasting of weather by a computer is known

numerical weather prediction

A halo around the Sun or moon indicates that rain may be on the way because the halo indicates the possible approach of a...

occluded and warm front

What is a Nor'Easter and where does it originate?

originate along the Gulf Coast or the south Atlantic coasts Low pressure center moves up along the east coast Most frequent and violent in September and April when large temperature contrasts exist. Bring rain and heavy snowfall to the northeast

The vertical structure of the hurricane shows an upper-level ________ of air, and a surface ________ of air.

outflow, inflow

In what part of the world are tropical cyclones least likely to form due to cooler sea surface temperatures and too much wind shear in the troposphere?

over the south atlantic

when thunderstorms are training, what are they doing?

passing over the same area, one after another

What is the least accurate forecast method of predicting the weather two days into the future during changeable weather conditions?

persistence forecasting

From largest to smallest what is the correct order of "Scales of Motion"?

planetary, synoptic, mesoscale, microscale

Strong storms that develop over water, poleward of the polar front, are called

polar lows

nowcasting

present - 6 hours

Which weather forecast predicts that the future weather will be the same as the present weather?

presistence forecast

The contour lines drawn on a 500 mb chart are lines of constant​ _______

pressure

At many locations, the wind blows more frequently from one direction than from any other. The ____________________ is the name given to the wind direction most often observed during a given time period.

prevailing wind

RUC

rapid update cycle (numerical modeling)

real-flank downdraft

rear portion of a mesocyclone's downdraft

At a warm front, the warm air

rises and cools

what do all thunderstorms require

rising air

What must a thunderstorm possess in order to produce a tornado?

rotating updrafts

sound of thunder when its far away

rumbles

The greatest improvement made in forecasting skill during the past thirty years is in forecasting

severe storm warnings for hurricanes and tornadoes

How do severe thunderstorms differ from ordinary thunderstorms?

severe thunderstorms have a tilted updraft in the mature stage

analogue forecasting works best with

severe/winter weather events

S-REF

short-range ensemble forecast (numerical modeling)

How does Aneroid work when measuring pressure?

small box compresses and expands with changing pressure

Pressure readings from different elevations must be reduced to sea level to be able to compare them. Why?

small changes in elevation produce large pressure changes

What is the Microscale?

smallest scale, includes tornadoes and smaller winds (eddies), less than 1km, last from a few minutes to an hour

During the winter as you travel toward a warm front, the most likely sequence of weather you would experience is

snow, sleet, freezing rain, rain

Folklore Forecasting

some are reliable, others are not - groundhog day - weather poems

Regions where air masses originate are known as ____________________.​

source regions (usually flat with light winds can be land or water)

If you live in the Northern Hemisphere and a region of surface low pressure is directly west of you, the surface wind direction at your home would probably be either__________ or ____________.

south or southeast

The position of the Pacific high over the North Pacific Ocean shifts _______ in winter and ________ in summer.

southward; northward

Suppose the eye of a hurricane passed directly over you, and you survived the experience. If winds were from the northeast as the eye wall first approached you, from what direction did the winds blow when the eye wall reached you the second time?

southwest

doppler radar

specialized weather radar that sees wind (velocity) and precipitation (reflectivity) -- Note: It can Indicate formation of WALL CLOUDS by looking at wind direction

Which of the following characteristics is not a characteristic of the tropical atmosphere

strong seasonal variations in temperature true: -- strong seasonal variations in precipitation --weak variations in diurnal temperature --more water vapor in the air --generally more unstable than the mid latitudes

What does a meteorologist typically examine when making a forecast?

surface charts, upper air charts, radar displays, satellite imagery

Polar Cell - what is it and where is it located?

surface winds move north to south and turn right: Polar Easterlies from 60 to 90 degrees Air sinks at polar high because it is cold and dense. Air moves toward equator at the surface. Air meets flow from the subtropical highs at the polar front and rises

Ferrell Cell - what is it and where is it located?

surface winds move south to north and turn right: Westerlies from 30 to 60 degrees found in mid latitudes (area with large temp contrasts) air sinks over the subtropical high, air travels toward the pole at the surface, air rises as it meets the polar cell and returns aloft

Ocean-atmosphere interactions, where warm or cold surface ocean temperatures can influence precipitation patterns in a distant part of the world, are called ____________________.​

teleconnections

Equation for Pressure =

temp X density X constant "Equation of State" also known as "Ideal Gas Law"

Which forecast method compares past weather maps and weather patterns to those of the present?

the analogue method

how does lightning work?

the buildup of negative charges at the cloud base will eventually overcome the insulation of the air and "electricity" is created! (((:

What is a "gust front"?

the cold outflow from a thunderstorm

What is dendrochronology?

the dating and study of annual rings in trees

frontogenesis

the formation, strengthening, or regeneration of a front.

stepped leader

the initial spark of lightning that leaves a storm clouds base - very faint, almost invisible - positive charge from the ground meets the negative stepped leader in the middle to create a lightning bolt (return stroke)

What is the "General Circulation of the Atmosphere?"

the long-term average of the wind over the globe. Provides insight into large-scale conditions over different parts of the globe and their underlying causes

climatology

the long-term average of weather conditions are used to predict the weather for a given day

grid point

the point in the middle of numerical grids - all the mathematical equations are solved at each grid point

Wintertime mP air masses are less common along the Atlantic coast of North America than along the Pacific coast mainly because

the prevailing winds aloft are westerly

A forecast of "chance of precipitation" means

the probability of precipitation is between 0 and 20 %

According to the textbook, which of the following best defines the tropics

the region between 23.5° N and 23.5° S latitude

trend method uses

the short-term trend of temperature or precipitation based on nearby observations

​The size and shape of a turbulent eddy depends upon

the size and shape of the obstacle

Vorticity refers to

the spin of air parcels

derechoes occur most often in

the summer (July)

What will occur when an upper-level low lies directly above a surface low

the surface low will probably weaken

How do supercell thunderstorms differ from ordinary cell (air-mass) thunderstorms?

the updraft in a supercell thunderstorm is longer lasting and rotates

return stroke

the upward flow of current that we see (as lightning)

Which of the following statements best describes a warm-type occluded front?

the warmest surface air is found to the west of it

frontolysis

the weakening or dissipation of a front.

persistence forecasting works "OK" if

the weather pattern in "blocked"

persistence forecasting depends largely on

the weather patterns and your location

Upper-level winds in the middle latitudes of both hemispheres generally blow from ________.

the west

A stationary front does not move because

the winds blow parallel to the front

Which type of weather "alert" would be issued when severe weather is actually occurring or is imminent within the specified forecast area?

tornado warning

What are the first three stages of a developing hurricane (from first stage to third stage)?

tropical disturbance, tropical depression, and tropical storm

Just before a storm becomes a fully developed hurricane, it is in the ____ stage

tropical storm

T or F: Drylines are most frequently observed in the western half of Texas, Oklahoma, and Kansas, especially during spring and early summer. In these locations, drylines tend to move eastward during the day, then westward toward evening.

true

T or F: Friction is not restricted to solid objects; it occurs in moving fluids as well.

true

T or F: Strong winds blowing over vegetation results in rapid water loss in the plant.

true

T or F: The altimeter and barograph are two types of aneroid barometers.

true

T or F: The difference in surface wind speed between morning and afternoon is typically greater on a clear, sunny day than on a cloudy, overcast day.

true

what produces rotation?

turning/changing directions of winds with height

extended forecast

up to 90 days

flanking line

updraft/food supply for the mesocyclone

What does Pilot Balloon (Weather Balloon) measure?

upper level winds

short term forecast

usually pretty accurate

Suppose there are two cloud layers above. The lower cloud layer is moving from a westerly direction, while the higher cloud layer is moving from a northwesterly direction. From this observation you conclude that the wind is ________ with height and ________ advection is occurring between the cloud layers

veering, warm

derechoes usually associated with

very buoyant, warm air mass

You are in upstate New York and observe the wind shift from easterly to southerly. This shift in wind is accompanied by a sudden rise in both the air temperature and dew-point temperature. This means a _________ front passed.

warm

Suppose it is warm and raining, and a cold front is moving toward your location. Directly behind the cold front, it is cold and snowing. Still further behind the front, the weather is cold and clearing. What would a persistence forecast for your area for twelve hours from now be if the front is scheduled to pass your area in six hours?

warm and raining

What is the main source of energy for a hurricane?

warm ocean water and release of latent heat of condensation

Know and understand Chinook Winds

warm, dry wind that descends the eastern slope of the rocky mountains, strong westerly winds aloft flow over a north/south mountain range

_________ regions have higher heights on pressure charts

warmer

Compared to an mP air mass, mT air is:

warmer and more moist

1. observations

weather data collected all around the globe - look at current conditions

WRF

weather research & forecast model (numerical modeling)

For a surface storm system (a wave cyclone) to intensify, where should the upper-level low (or trough) be located?

west of the surface low