Intro To Severe Weather Exam 2
Gust Front
A boundary found ahead of a thunderstorm that separates cold storm downdrafts from warm humid surface air. Winds in this phenomenon are strong and fast.
Air parcel
A bubble of air of no definite size, assumed to retain its shape and general characteristics as it rises and sinks into the atmosphere.
False
A cold pool is a thunderstorm feature found only with MCS thunderstorms. Select one: True False
stable; unstable
A conditionally unstable atmosphere is______ for an air parcel that is unsaturated and ______ for an air parcel that is saturated.
Mesocyclone
A cylinder of cyclonically flowing air that form vertically in a severe thunderstorm. They measure about 3 to 10 kilometers across. About 50% of them spawn tornadoes. They can also form a dome at the top of the storm cloud.
Roll Cloud
A dense, cigar shaped cloud found above the gust front of a thunderstorm. Air within the cloud rotates around the long axis.
Serial derecho
A derecho produced by multiple bow echoes embedded in an extensive squall line that sweeps across a large area. Most common type.
Multi-cell cluster.
A group of thunderstorm clouds which merge together to form one large storm with multiple cells.
Rex Block
A high-presssure system located pole-ward (north) of low-pressure systems. Remain stationary until one of the height centers changes intensity to unbalance it. Makes stormy weather near low pressure, with dry conditions near high pressure.
Mesoscale Convective Systems (MCSs)
A large cloud system that is associated with a group of thunderstorms that produce a continuous area of precipitation of rain with 100 km or more in width and length. They can last for many hours or days, take different shapes and styles, and all depend on the large scale environment. These are responsible for most of the rainfall in the Summer time.
Shelf cloud. It appearse like this because of the rain cooled air spreading out from under the squall line, acting as a min cold front. The cooler dense air forces the warmer, less dense air, up. The rapidly rising air cools and condenses creating the shelf cloud.
A low hanging arc of cloudiness along a squall line.
Precipitation water (PW)
A measure of the depth of liquid water at the surface that would result after participating all of the water vapor in a vertical column over a given location
Stability
A measurement of how the atmosphere resits or encourages vertical motion (rising or sinking air).
Squall line
A multi-cell thunderstorm ahead or along a cold front.
Adiabatic process
A process where the sun heats up an air parcel.
Wall cloud
A rotating cloud forming below the rain-free base below the main storm tower updraft. Often located on the flank of the precipitation. Have visible rotation under a storm.
Polar Orbiting Satellites.
A satellite orbiting a latitudinal motion that moves over the north and south poles. They orbit Earth multiple times a day, but the orbital tracks do not repeat on a daily basis They provide very detailed images and a good look at the polar regions. However, they do not see the whole earth's surface and change paths due to the earth's rotation.
Radiosonde
A small instrument package suspended below balloons filled with either hydrogen or helium. As it is carried by the balloon, it measures pressure, temperature, and relative humidity. It can also measure wind speed and direction by recording its position.
Connective Outlooks
A technical narrative and graphic depicting thunderstorms across the U.S., with large amounts of technical language.
Multi-cell line (Squall line)
A thunderstorm that expands laterally for hundreds of miles, and lasts for many hours, producing dmaaging winds and hail.
Gradient
Any change in any particular weather element like pressure and temperature.
The separation of an electrical charge and generation of electric field, which ice, hail, and semi-frozen water drops being essential
According to the leading theory on thunderstorms, what are some key factors that lead to lightning development?
Before and after the storm has peaked. Lightning can even strike someone more than 10 miles away form the location of rainfall.
According to thunderstorms, when is lightning most likely to strike someone and where?
Positive vorticity advection
Advection that normally means that air is being moved upwards by the atmosphere counterclockwise.
Explosive Expansion
Air expands so rapidly that it compresses the air in front of it, forming a shock wave similar to a sonic boom.
True
Air motions are driven by pressure differences that develop due to the uneven solar heating that occurs across the earth's surface. Select one: True False
300 mb chart
Air pressure chart used to locate jet streams and contours of equal wind.
True
An MCS can evolve to develop a squall line. Select one: True False
Downbursts
An area of strong, often damaging wind produced by a convective downdraft.
the updraft is on the rear flank of the storm provides a barber pole or corkscrew appearance to the cloud. Precipitation is sparse or well removed from the updraft and/or often is transparent.
Are low precipitation supercells like?
True
Automated Surface Observing Systems (ASOS) and Automated Weather Observing Systems (AWOS) work nonstop, 24-hours a day, to collect atmospheric data. True or False
True
Automated Surface Observing Systems measure atmospheric properties such as temperature, visibility, wind direction, precipitation type and precipitation rate. Select one: True False
850 mb
Chart where moisture levels are used to forecast precipitation and provide relative humidity.
700 mb chart
Chart where we look at both moisture and vertical motion to find and forecast precipitation, which could also indicate relative humidity.
Skew-T Log-P Diagrams
Charts that show the temperature, dew point, and wind speed/direction. These can be used to find meteorological conditions of the upper air.
True
Clouds tend to form on the windward sides of mountains because the mountains act as a lifting mechanism. Select one: True False
Omega Block
Combination of two cutoff lows with one blocking high sandwiched between them. Can lead to flooding and droughts.
Moist/saturated adiabats
Curved lines moving from left to right. Represent the rate saturated air cools as it rises.
straight-line wind damage
Damage as a result of the force of the down draft from a thunderstorm spreading horizontally as it reaches the earth's surface on a squall line.
Microbursts
Damaging wind that starts off as a really strong downdrafts.
Progressive derecho
Derecho's assoiated with short line thunderstorms., that typically measure 40-250 miles in length. Mainly happen in summertime, and act parallel to stationary fronts. Starts out small and narrow, but grow over time.
Low dew point derechos
Derecho's which occur in environments of very limited moisture. Often occur in the late fall and early spring.
Hybrid derecho
Derecho's with a mix of progressive and serial types.
Mesoscale Discussions (MCD)
Describes what is currently happening, what is expected in the next few hours, the meteorological reasoning forecasts, and when/where weather watches will be placed for severe thunderstorm potential.
Moving Geo "stationary" Satellites
Despite being stationary relative to the earth, their position can be moved. When a new one comes in, old ones are put into different areas, so they have rockets to help them move.
True
Extratropical cyclones are parent storms from which much of middle latitude severe weather develops. Select one: True False
True
Extratropical cyclones develop as a direct result of accelerations created by imbalances between the pressure gradient force and the Coriolis force, primarily at the jetstream level. Select one: True False
synoptic (continental scale)
Features on a weather map that More specific information that is hard to intercept, such as where jetstreaks are, where smaller scale features in a trough might be, where vorticity advection may.
west
For an extratropical cyclone to intensify, the upper-level trough axis should be located to the __________of the surface low.
Probabilistic forecasts
Forecasts which provide a chance that something will happen like "50% chance of rain". Almost every forecast we do, we assign some type of probability.
Quantitative forecasts
Forecasts with numbers behind it like "It will be 90 degrees and there will be 7 inches of rain"
True
Frontal squall lines tend to be associated most often with strong straight-line winds. Select one: True False
True
Geostationary satellites are located above the equator, and rotate with the earth once a day. Select one: True False
about 22,000 miles
Geostationary weather satellites are placed in orbit over the equator at a distance of how many miles above the Earth's surface?
Supercells
Highly organized storms characterized by updrafts that can attain speeds over 100 mph (160 km/h) and are able to produce giant hail with strong or even violent tornadoes
1. At the start, in a normal thunderstorm there's a cool downdraft that spreads horizontally across the earth's surface. 2. The spreading cool air on the surface forces lighter moist air up into the atmosphere, forming the gust front. 3. The force up air starts to create a new thunderstorm cell, with rain from this new storm cooling the air blelow to maintain its strength. 4. As the cold wind inreases in size, it creates more air inflow on the traililng side of the thunderstorm, causing the updraft to tilt that awy. 5. This allows for further cloud expansion and coverage, ading more to the cold pool of air, repeating teh earlier process. This tilting also creates the bow of the bow echo.
How are bow echos created?
It is created by a family of downbursts clusters within long-lived thunderstorm complexes that produce bow echoes.
How are derechos produced?
When an electric field couples with a magnetic field. They are perpendicular to each other and to the direction of the wave.
How are electromagnetic waves formed?
Outflow boundaries are a result of the rush of cold air as a thunderstorm moves overhead.
How are outflow boundaries form?
On these models, forecast points are laid out in a grid around the area they cover, with the distance between the centers of the grids (grid points) vary with scale and design of the model. The more grid points, the more specific results. Then a variety of weather data is input, where it will show and predict the state of the atmosphere in time.
How are weather forecast models oriented and modeled?
4 to 6 miles
How big are downburstsz/
As lightning occurs, it creates static on the radio, so the more static the more like a thunderstorm in approaching.
How can AM radio band's help determine how closer thunderstorms are?
They can add more weight onto a plane and change the airflow. When a plane is trying it land it can create additional lift at the edge of the microburst, causing it to lift more. When the pilot tries to correct, the downburst can suddenly push down on the plane, causing the plane to dip down more.
How can microbursts cause plains to crash?
When a air mass thunderstorm forms over a frontal cyclone, the cold front of the cyclone, or dry line, will push warm air horizontally and vertically. If it's suitably humid and extending east, it will supply the storm with more moisture and energy, allowing it to stay severe.
How do air mass thunderstorms get turned into severe thunderstorms?
Because moist air is less dense than dry air, drylines will help lift up the less dense moist air over the drier, more dense air.
How do dry lines affect moist and ry air?
Dry air will heat up the air behind and ahead of it, causing moist air to become even less dense and rise more easily along the front, causing the moist air to rise and create thunderstorms.
How do drylines create thunderstorms?
Transfers warm and cold air between the poles and tropics. The slowness of longwaves can lead to long periods of different types of weather.
How do longwaves affect the air and weather?
Clean band
Infrared band that is less sensitive than other channels to water vapor. It can see through clouds to view ice, improving corrections to atmospheric moisture and estimating cloud particle sizes.
First Eartarth is unevenly heated by the sun, creating different levels of pressure next to one another. Alternatively, there's also irregular air movement around mountains, where air has to ride up mountains because it can't go through it. This creates vertical and horizontal imbalance, with wind speeds changing in different ways to try and balance things out.
How do longwaves form?
Microbursts are created from the frictional force created from the storm clouds. It is also fueled by evaporation in the downdraft. IF there is a lot of evaporation, there is a lot of cooling, which forms a cooler and more dense downdraft, which causes it to move faster, stronger, and even spread faster with strong winds.
How do microbursts created?
A windshear pushes a single-cell thunderstorm to move with the gust front, and moves the updraft so the downdraft does not cut it off by tilting the gust front boundary. As the single-cell moves, more thunderstorms form and bunch together, forming a multi-cell.
How do multi-cell thunderstorms form?
Satellites will measure the temperature water vapor ahs gained from absorbing radiation at specific frequencies.
How do satellites measure water vapor?
Squall lines dissipate when the updraft along the cold pool tilts too much, causing convectoin to get weaker and weaker.
How do squall lines dissipate?
These normally form where there are initially a lot of single cell thunderstorms that are going up. In this scenario the updraft and downdraft are not on top of each other and they slowly start to form on top of each other. The storms come together and form a squall line, with the cold pool and gust front creating a structure ahead of the storms, which creates continuous lifting which helps maintain the linear appearance of a thunderstorm.
How do squall lines normally form?
Whenever the thickness lines cross isobars, that indicates gustiness since the wind speed is controlled by the pressure gradient
How do thckness lines indicate gusty wind?
There is positive vorticity anytime we have counterclockwise rotation, meanwhile we gain negative vorticity when there is clockwise. Just having a map of vorticity can tell us where spin is in the atmosphere.
How do we gain positive or negative vorticity?
No matter what if the atmosphere is stable or the air parcel is moist or dry, air parcels will always sink back to their starting point. This happens a lot with temperature inversions. Temperature inversions are always absolutely stable
How does absolute stability affect air parcels?
1. The updraft carried up liquid water droplets from the bottom of the storm 2. The downtraft carries hail and ice from the top of the storm. 3. They collide, causing water droplets to freeze and release heat 4. The heat keeps the hail and ice slightly warm, formign graupel. 5. The graupel collides with more water droplets and ice particles 6. Electrons are sheared off of the ascending particles and collect on the descending particles. 7. The negative charge of the electrons gives the storm a negatively charged base and positively charged top
How does charge separation in a thunderstorm form?
This differential heating can create adjacent areas of air that will have different temperatures. While cooler air will start to sink, warmer air will start to rise due to a lack of density, creating thermals.
How does differential heating, the way the sun heats different parts of the surface unevenly, affect air?
1. Thunderstorms gather along areas of positively charged particles along the ground. 2. Positively charged particles start to rise up along taller objects. 3. A "stepped leader" of negative energy descends from the storm. 4. Once the positive and negative energy mix, they create an electrical transfer (known as negative lightning).
How does lightning develop between the cloud and the ground?
After charge separation, there are sets of positive and attractive charges that are separated from each other, forming an electrical field between the top and the base. If there is a large amount of charge, the atmosphere can no longer contain it and lightning forms.
How does lightning form within a cloud?
In an orographic lifting model, the side of the mountain with upwind will likely be lush and green because of the cooler more moist air fueling plants, However as the air and clouds go over the mountain, the air parcels get compressed and start to heat up and become more dry, leaving that side of the mountain barren and dry (this results in a rain shadow)
How does orographic lifting affect mountains?
In warmer air, sound moves faster and farther. In cooler air, sound moves slower and at shorter distances.
How does sound affect the traveling of air?
When you loop these images you can see how the clouds evolve and change. Depending on the angle of the sun, you can start to see shadows form at different angles, allowing us to see more dimensions of the clouds. Based on how fast the clouds are moving, you can find jet streaks. You can also use this to find frontal boundaries.
How does visible imagery help observe the weather?
In an ordinary cell, the updraft will hold up growing raindrops. However, when it gets too much for the updraft, the raindrops will fall. The force of the raindrops will then slowly start to turn the updraft into a downdraft.
How is a downdraft formed in an Ordinary Cell?
As an updraft lifts a column of rotating air,(created from wind shear) this provides two rotations to a supercell, cyclonic or counter clockwise rotation and an anti-cyclonic of clockwise rotation. Though directional shear amplifies cyclonic rotation while diminishing anti-cyclonic. As the air rises more, it becomes stretched and narrower.
How is a mesocyclone created?
At certain pressure levels (called mandatory levels) and anything there's a significant temperature, humidity, or wind change, the radiosonde will record the temperature and relative humidity. When the radiosonde drops, data is compiled into a series of five-digit groups comparing temperature, dew point depression, and wind speed/direction the different labels.
How is a skew-T plot created?
Dirty band
Infrared band that is more sensitive to water vapor. It is used to compute split window difference. It can highlight moisture differences between areas
As a funnel starts to descend, water vapor in it condenses into liquid droplets. The droplets make the funnel visible and it takes the color of the cloud droplets. The rotating air will begin to move dust and debris around it before the funnel touches the ground. Once the funnel touches the ground, it's officially a tornado. However the tornado after a certain amount of time will lose intensity, tilting, contorting, and eventually dissipate once the condensation funnel decreases with size.
How is a tornado created?
Several hundred miles
How long is a typical frontal squall line?
Lapse rate
How much the temperature is changing as you go up with height, so it defines the vertical rate of change in temperature.
d.zero everywhere on earth.
If the earth did not rotate, the Coriolis force would be: Select one: a.strongest at the poles and zero at the equator. b.strongest at the equator and zero at the poles. c.strong and negative everywhere on earth. d.zero everywhere on earth.
Visible imagery
Imagery which uses light that reflects off of clouds. They do not work at night time because there is no visible light from the sun that can be reflected back at space.
Concentrated in a relatively small area
In a downburst, the heaviest rain is ___________. Select one: a.absent b.spread out over a large area c.concentrated in a relatively small area
True
In addition to height contours, the 300 mb map typically shows wind speed and can be used to identify the location of the jet stream. Select one: True False
Do not touch anything which is connected to the outside and can produce electricity. Do not use electrical appliances at all.
In case of lightning, when inside a vehicle or building what are some important tips of survival?
False
In extratropical cyclones, force imbalances at jetstream level produce convergence aloft above the low-pressure center that cause the surface low to intensify. Select one: True False
True
In the absence of divergence aloft, a surface low-pressure center will weaken due to convergence in the friction layer. Select one: True False
True
In the mountain regions of the western United States the 850 mb surface does not exist at many locations and therefore no data is reported on an 850 mb map. Select one: True False
Conditionally unstable
In this a dry air parcel is stable and will not rise, but as soon as a cloud form and moisture is added and there's condensation, the dry air parcel will become an unstable air parcel. The air parcel needs something to get it moving initially. The air parcel will sink if it is dry.
Conditional Instability
In this state, small forces may move the parcel slightly, but it will always return back to its original position. However, once a strong enough force is applied and the parcel moves far enough, it will continue to move away from its original position.
Ozone band
Infrared band that provides information about the dynamics of the atmosphere near the tropopause. In the future it will provide the amount of ozone in a column, which can provide information that can forecast areas of atmospheric turbulence.
Clean band
Infrared band that's less sensitive than other channels to water vapor. It can see through clouds to view ice, improving corrections to atmospheric moisture and estimating cloud particle sizes.
Carbon Band
Infrared band used to generate other derived GOES imagery. Used for air temperature estimation, determining the location of the tropopause and cloud observations for cloud top height, determining wind speed and direction, and supplementing ASOS observation.
True
Isolated thunderstorms that form in the absence of vertical wind shear are called airmass thunderstorms. Select one: True False
Environmental lapse rate
It is the vertical change in temperature of the environment. Just the air around the outside environment. Typically temperature decreases in height.
Positive lightning (makes up 5% of all strikes)
Lightning that originates from the top of the thunderstorm with a high positive charge
Veggie Band
Near Infrared band that observes vegetation, and land characteristics when determining fire and flood potential. Water is very absorbing at this wavelength which makes it appear darker.
Longwaves
Mid-latitude westerly winds which move in large wavy patterns that control hemispheric weather patterns
500 mb chart
Most valuable chart that ranges in elevation from 16,000 feet to 20,000 feet. Considered at the middle of the atmosphere.Used to measure vorticity and humidity
Mesoscale motion
Motions on a weather map that take place inside synoptic motions.
Cirrus band
Near Infrared band that is centered in a strong water absorption of the electromagnetic spectrum, meaning the radiation from water vapor is absorbed, so it's not routinely visible at this wavelength. Provides daytime sensitivity to high, very thin cirrus under most circumstances. Distinguishes between low and high clouds.
Cloud Particle Size Band
Near Infrared band that is sensitive to temperature and able to see the slight thermal differences between the ground and low stratus clouds.Useful for identifying night time fog and low clouds, as well as volcanic ash and estimating sea-surface temperatures.
Snow/Ice band
Near Infrared band where snow and ice surface are strongly absorbing this wavelength, with radiation being absorbed, ice crystals appear darker than clouds which consist of liquid water. At night, forest fires can be noticed against the dark background.
Weather Satellites
Obtain information about the atmosphere through remote sensing, where we can learn about objects without being in contact with them.
isotherms
On a surface map, a strong temperature gradient exists in a location where ______ are packed closely together.
False
Over land, the turning of air across isobars due to friction is on the order of 80 to 90 degrees. Select one: True False
Cut-off low
Persistent low pressure areas isolated from main airflow. Move south on the west side of troughs extending towards the equator. Short wave pulls the trough out of the main airflow, forming a low pressure circulation.
The Advanced Baseline Imager (ABI)
Provides visible and infrared views of the earth on the GOES East satellite. It's produced at 16 different wavelengths/channel.
Virga
Rain that evaporates before it hits the ground. Normally found in dry downdrafts.
dry adiabatic lapse rate
Rate at which a dry adiabat expands and cools at a rate of 9.8 degrees celsius every 1,000 meters until its saturated.
True
Rawinsondes are normally launched twice a day at stations worldwide. Select one: True False
Upper air
Refers to earth's atmosphere above 5,000 feet. It's where we get rain, drought, wind, heat, and cold at earth's surfac
Meso scale
Regional scale features on a weather map.
Height Contours
Represent the altitude of pressure levels. Through the line, pressure is all the same. The higher the line is, the higher the altitude and the difference in air density. Indicated by brown dashed lines with ridges.
Geostationary Satellites
Satellites with a high altitude of around 22,236 miles, that only fully orbit the earth once a day. Appeared stationary and basically seemed to hover continuously over one position on earth.
Ordinary Cell
Short thunderstorms with a one-time updraft, and a one-time downdraft. Not very severe weather, wiht maybe a bit of hail and gusty wind.
Dry Adiabats
Slightly curved lines moving from the lower left to upper rights. They represent the state of unsaturated air cooling as it rises.
Burst swaths
Small pocket of extreme wind within a microburst, ranging from 50 to 150 yards.
Single-cell thunderstorms
Small thunderstorms which indicate there is enough instability for a storm to form, but not enough wind shear to get worse. Only last for an hour, with one primary updraft and downdraft, with minimal rainfall.
Microbursts
Smaller pockets of more intense wind in downbursts
Wind Staff
Staffs for plotting the wind speed and direction at the different pressure levels based on the tracked position of the radiosonde carried by the wind.
Newton's first law of motion
States that an object will stay at a constant motion unless another force is exerted on that object
Classic Category
Supercells with a large, flat updraft base with striations or banding seen around the periphery of the updraft. They have heavy precipitation which falls adjacent to the updraft. Has the potential for strong, long-lived tornadoes.
Orographic Uplift
THe uplifting of an air mass by a topographic structure, which causes cooling of the air mass
Rain/snow line (540 mb)
The 1000-500 mb thickness value used to determine rain versus snow, where the poleward side determines snow, with the equator side determining liquid.
False
The 300 mb level is located at approximately 10,000 ft. altitude. Select one: True False
True
The 500 mb surface will be closer to the earth's surface over central Canada compared to over southern Mexico. Select one: True False
True
The 850 mb surface will be closer to the earth's surface over central Canada compared to over southern Mexico. Select one: True False
True
The ASOS suite of instruments reports cloud height and amount, visibility, precipitation type, intensity, and accumulation, obstructions to vision such as fog or haze, sea-level pressure, altimeter setting, temperature, dewpoint temperature, and wind direction, speed and character (gusts, squalls). Select one: True False
True
The Coriolis force increases as the wind speed increases, except directly on the equator where the Coriolis force is zero. Select one: True False
False
The National Weather Service forecasts and identifies severe thunderstorms but they do not have specific defined criteria to identify what constitutes a severe thunderstorm. Select one: True False
Thunder
The acoustic shock wave resulting from the extreme heat generated by a lightning flash.
200 mb
The air pressure everywhere.
Ordinary mixing ratio
The amount of water vapor in the air where the dew point temperature line crosses the mixing ratio line.
lifting condensation level (LCL)
The base of a thunderstorm cloud is found at the ________.
Dry lines
The boundary between two air masses of different moisture content and divides warm, moist air from hot, dry air.
Wind Shear
The change in wind speed or direction with height
True
The infrared channel on a GOES satellite can be used to estimate the temperature of cloud tops. Select one: True False
lifting/lifted condensation level (the base of the cloud) (LDL)
The level at which the temperature matches the dew point, with water vapor condensing and becoming liquid water at the dew point to form clouds
Saturation mixing ratio
The maximum amount of water vapor that can be in the air at any given level and is found where the temperature line cr
Thickness
The measurement of distance (in meters) between two constant pressure surfaces.
True
The moist adiabatic lapse rate normally has a smaller value than the dry adiabatic lapse rate. Select one: True False
Advection
The movement of any variable from place to place by the wind.
moist adiabatic lapse rate (cools at 6 degrees per kilometer
The rate a saturated air parcel will cool, with cooling being slowed by the release of latent heat from water vapor turning into liquid water.
Vorticity
The rotation of a fluid which can be in any three 1 dimensional direction. Move counterclockwise
Absolute instability
The state of the atmosphere When a force is applied to the parcel, it begins to move on its own without any additional force.
Cloud-Top Phase band
This infrared band is similar to other bands, however, it can also derive cloud phases during both day and night. Clouds can go through phases such as liquid water, supercooled water, and frozen.
visible
This satellite channel measures solar radiation reflected from the underlying surfaces.
Supercell thunderstorms
Thunderstorms that are dominated by a single rotating updraft and a pair of downdrafts. Form in very unstable environments with strong wind shear.
Bow echoes
Thunderstorms that assume a curved shape that arise from a cluster of storms.
Air mass thunderstorms
Thunderstorms that develop in late afternoon hours when surface heating produces the maximum number of convection currents in the atmosphere.
Waterspouts
Tornadoes that travel across lakes or oceans
Positive tilted Troughs
Troughs extend from the lowest pressure northeast to southwest in the Northern hemisphere (southeast to northwest in South hemisphere). Produce the least weather.
Negative Tilted Troughs
Troughs which begin as positive tilted troughs, but get distracted into neutral (north-south) and then to its current state (northwest to southeast). Produce severe weather because there is strong southerly surface wind with its warm air underneath cold air in the upper atmosphere that creates unstable conditions.
Cirrus anvil
Upper part of the thunderstorm
Blue Band
Visible band that provides nearly continuous daytime observations of dust, haze, smoke, and clouds. It also measures "aerosol optical depths", helping air quality monitoring and tracking.
Red band
Visible band that provides observations for snow and ice cover, detection of severe weather, low-level cloud-drift winds, smoke, volcanic ash, hurricane analysis, and winter storm analysis.
Mid-level Water Vapor Band
Water vapor band that band can view levels as low as 500 mb, and is used for vapor tracking, jet stream identification, hurricane forecasting, mid-latitude forecasting, severe weather analysis, and mid-level moisture estimation.
Low-level Water Vapor band-
Water vapor band that looks deep into the atmosphere at levels as low as 750 mb. Useful for viewing and estimating low-level moisture and jet streak.s It can also be used to highlight volcanic plumes with sulfur dioxide.
Upper-level Water Vapor Band
Water vapor band used in upper level feature detection such as jet stream, troughs, ridges, and signs of potential turbulence.
Open waves
Waves with simple troughs and ridges, giving off an 'open' appearance They move west to east.
Shortwaves
Waves within longwaves that are less than half its size. Move east downstream faster than longwaves. This causes longwaves to distort and change shape, deepening longwave troughs and flattening ridges.
Synoptic motion
Weather motions on a weather map such as pressure, surfaces, ridges, and troughs.
(1). Unequal warming of the surface of the Earth. (2). Orographic lifting due to topographic obstruction of air flow. (3). Dynamic lifting because of the presence of a frontal zone.
What are potential causes of vertical lifting?
Watches are large areas, 20,000 to 40,000 square miles, and are issued by county. They are numbered sequentially (the count is reset at the beginning of each year). A typical watch has a duration of about four to six hours but it may be canceled, replaced, or re-issued as required.
What are severe weather watches?
-It normally moves from left to right because of the cyclone -Updrafts move up and over downdrafts -At the back of the cloud, updrafts become downdrafts -Downdrafts produce gust fronts near the suraface, increading wind speed.
What are some of the features of a severe thunderstorm that differentiates it from a normal thunderstorm?
It provides explicit information regarding the timing, the greatest severe weather threat and the expected severity of the event.
What are some of the specific thinks connective outlooks can provide?
In unstable air, the air aloft is normally cold and dry. Meanwhile, the air close to the surface is warm and moist. This causes water vapor inside rising air parcels to condense, and start to form cumulonimbus clouds.
What are some of the vertical characteristics of unstable air.
Located in the same spot relative to earth View the entire earth at all times Record images quickly Can measure the motion of clouds since it's always in the same spot. Receive transmissions from free-floating balloons, buoys, and remote automatic data collection stations
What are the advanteges of a geostationary satellite?
Rear Flank Supercell - Low precipitation (LP) Classic (CL) Front Flank Supercell - High precipitation (HP)
What are the different types of Supercells?
Downdrafts produced by these storms can produce downbursts/outflow winds in excess of 100 mph (160 km/h), posing a high threat to life and property.
What are the downdrafts in supercell storms like?
Day 1- The risk of severe weather today through early tomorrow morning. Forecast is issued five times daily. Day 2- Continues form the ending of Day 1 for the next 24 hours. Issued twice daily. Day 3- Forecast for the subsequent 24 hours. Issued daily. Days 4-8- A weather area depicted in the days 4-8 period, depicting a 15-30% chance of severe thunderstorms.
What are the four convective outlooks?
There are two lines on the Skew-T. A red one representing dew point (Calculated from relative humidity) and a red one represents air temperature.
What are the lines on the Skew-T chart?
When the winds are veering or turning clockwise with height. This change in wind speed and direction produces storm-scale rotation, meaning the entire cloud rotates, which may give a striated or corkscrew appearance to the storm's updraft.
What are the most ideal conditions for supercells to occur?
Temperature Pressure Dry Adiabats Moist/Saturated Adiabats Mixing Ratio Wind Staff
What are the six basic sets of fixed lines that comprise the skew-t diagram?
Cumuls Stage Mature Stage Dissipating stage
What are the stages of the air mass thunderstorm?
1. Moist, unstable air is lifted vertically into the atmosphere. 2. The warm moist air cools because of adiabatic expansion. 3. The dew point is eventually reached, causing condensation and the formation of a cumulus cloud. 4. Continuous uplift occurs, turning the cumulus cloud into a cumulonimbus cloud, which produces different weather events
What are the steps in thunderstorm formation?
Mositre Instability A mechanism to lift the air.
What are the three ingredients needed to form a thunderstorm?
Serial Progressive Hybrid
What are the types of derechos?
Directional Wind Shear- Changing of wind direction with height (normally in a clockwise motion) Speed Wind Shear- Changing of wind speed with height (tends to create a bit of a rolling effect)
What are the types of wind shear?
Oceans, with warmer water along the east coast providing more moisture due to its heat.
What are the typical sources of moisture?
Buildings with exposed openings Convertible vehicles or vehicles with open cabs
What are the worst places to go in a thunderstorm in case of lightning?
Soundwaves going towards the air will refract back towards the ground, adding additional sound and making thunder louder
What can happen to soundwaves when temperature inversions occur?
You can use that to measure how deep the cloud is. The less clouds there are, the higher the temperature on the infrared because the surface tends to be much warmer.
What can infrared imagery help find?
Heating from the sun creating different air densities across the atmosphere, with a decreased in density causing air to rise.
What causes force of lift in the atmosphere?
Severe thunderstorm watches are blue with tornado watches in red.
What colors are tornado and thunderstorm severe weather watches?
West to east
What direction does wind normally move in?
the updraft on the front flank of the storm precipitation that almost surrounds updraft at times the likelihood of a wall cloud (but it may be obscured by the heavy precipitation) tornadoes that are potentially wrapped by rain (and therefore difficult to see), and extremely heavy precipitation with flash flooding.
What do high precipitation supercells normally have?
Environmental temperature
What do radiosondes provide?
An enhanced (ENH) risk of severe thunderstorms during the forecast period. This means a 10% probability for any tornado WITH OR WITHOUT 10% or greater probability of an EF2+ tornado, or 15% probability for any tornado, or 30% severe hail or severe wind probability WITH OR WITHOUT 10% or greater probability of hail 2" or greater in diameter, or wind gusts 75 mph or greater or 45% probabilty of severe hail or wind.
What does Severe Category 3 - Enhanced mean?
This means a 15% tornado probability AND 10% or greater probability of an EF2+ tornado, or 30% probability for any tornado, or 45% severe wind probability AND 10% or greater probability of a wind gusts 75 mph (120 km/h) or greater, or 45% severe hail probability AND 10% or greater probability of hail 2" (4.8 cm) or greater in diameter, or 60% severe wind probability, or 60% severe hail probability WITH OR WITHOUT 10% or greater probability of hail 2" (4.8 cm) or greater in diameter.
What does Severe Category 4 - Moderate mean?
30% tornado probability AND 10% or greater probability of an EF2+ tornado or 45% or greater probability for any tornado WITH OR WITHOUT 10% or greater probability of an EF2+ tornado or 60% severe wind probability AND a 10% or greater probability of a wind gust 75 mph (120 km/h) or greater.
What does Severe Category 5 - High mean?
that indicates a general high chance of thunderstorm formation
What does a measurement of about 1000 indicate for CAPE?
Light green- General Thunderstorms Dark green- Severe Category 1 - Marginal Risk Yellow- Severe Category 2 - Slight Orange- Severe Category 3 - Enhanced Red- Sevre Category 4 - Moderate Fuchsia- Severe Category 5 - High
What does each color on the connective outlook represent?
A 10% or higher probability of non-severe or near severe thunderstorms during the valid period. Could still cause damage.
What does the General Thunderstorms label represent?
This means a slight (SLGT) risk of severe thunderstorms during the forecast period. This means a 5% probability or greater tornado probability, or 15% probability for severe hail or severe wind probability WITH OR WITHOUT 10% or greater probability of hail 2" or greater in diameter, or wind gusts 75 mph or greater.
What does the Severe Category 2 - Slight mean?
A marginal (MRGL) risk of severe thunderstorms during the forecast period. This means a 2% probability or greater tornado probability, or probability for severe hail or severe wind.
What does the Severe category 1 - Marginal Risk mean?
the potential pathway and temperature that air parcel would take. It also indicates the potential temperature change of an air parcel.
What does the black line on a skew-t diagram indicate?
the closer the dew point is to the temperature
What does the distance between the dewpoint and temperature mean on a skew-T chart?
On the morning of Tuesday, April 9, 1991, a bow echo formed over eastern Arkansas and began to produce wind damage. As the day progressed, a serial derecho developed as the original bow echo raced northeast and expanded in scale, while an additional bow echo formed farther north.
What happened in "The West Virginia Derecho of 1991"
On Friday, March 12, 1993, a strong low-pressure system formed in the Gulf of Mexico. This low-pressure system continued to strengthen dramatically and moved northeast to the mid-Atlantic coastal region by Saturday evening, March 13th. It produced an intense squall line with bow echoes ahead of the system's cold front.
What happened in The "Storm of the Century" Derecho.
On May 27th, 2001 isolated supercell thunderstorms formed over western kansas. These would converge and form and into a bow echo storm system, which produced a derecho that did significant damage over the southern Plains.
What happened in the "People Chaser" Derecho?
On July 12, 1995, thunderstorms formed over southeast Montana and began producing winds that damaged home and barns and blew over a mobile home. As it traveled across North Dakota, it gained more power. It would eventually become a bow echo storm wih high winds over Fargo, blowing down millions of trees.
What happened in the "Right Turn" Derecho?
The wind storm produced significant damage over a broad swath from the high plains of western Kansas to the foothills of the Appalachians in eastern Kentucky. It als ohad flash flooding, and a mesoscale convective vortex, accompanied with several strong surface winds
What happened in the May 8, 2009 Super Derecho
On July 14, 1995 thunderstorms producing severe weather were occurring over Upper Michigan and adjacent portions of Ontario, Canada near Sault Saint Marie. By late evening the storms had evolved into a bowing line just northwest of the Mackinac Bridge in Michigan. At 10:17 PM EDT, the thunderstorm gust front hit the bridge and a gust to 90 mph (145 km/h) was measured.
What happened in the Ontario-Adirondacks Derecho?
During the early morning of Tuesday, July 22, 2003, a derecho formed over north central Arkansas and moved rapidly east-southeast, reaching northern Alabama by mid-morning. It would soon travel over alabama, georgia, and carolina, with thousands of tressed damaged and blow down.
What happened in the mid-south derecho of 2003?
Parcels of warm humid air rise and cool to form c cumulus clouds. The clouds are the result of condensation and deposition which releases large quantities of latent heat. The added heat energy keeps the air inside the cloud warmer than the air around it. The cloud continues to develop as long as more humid air is added to it from below by updrafts. Updrafts dominate the circulation patterns within the cloud.
What happens in the cumulus stage of an air mass thunderstorm?
Air currents within the convective storm start to mainly consist of downdrafts, which cuts off the supply of warm air created by the downdraft. This slowly deplets the storm more and more.
What happens in the dissipating stage of a thunderstorm?
Updrafts reach their maximum altitude and precipitation begins to form. The storm is at it's most intense as a cumulonimbus cloud, which forms an anvil shape, as strong winds spread ice crystals to the top of the cloud. There is a mix of both updrafts and downdrafts keeping the storm alive.
What happens in the mature stage of a thunderstorm?
When a tornado occurs, the mesocyclone lengthens vertically, constricts, and spirals down to the ground surface.
What happens to a mesocyclone whenever a tornado forms?
Water vapor condeses from cooling. Heat is released, affecting the rate of cooling (which these lines represent). Near the surface, as saturated air rises, it expands and begins to cool at a rate of about 4°C per 1,000 meters. As it rises, the cooling rate decreases because there is less water vapor.
What happens when air is at 100% relative humidity?
In a stable atmosphere, rising parcels become cooler than the surrounding environment, slowly stopping. In an unstable atmosphere however, the temperature of the parcel is higher than the surrounding environment and continues to rise. In both, the parcel's cooling is fixed, so stability and instability are based on vertical temperature. We also assume that the ratio of moist air to dry air in the parcel stays the same as it moves.
What happens when an air parcel rises through the air in both a stable and unstable atmosphere?
All of the above are available from a sounding.
What information about the environment of a supercell is not available from a sounding? Select one: a.CAPE b.low-level jet c.capping inversion d.vertical wind shear e.All of the above are available from a sounding.
Rain-cooled dense air that acts as a mini-cold front, which operates similar to other fronts by lifting warm moist air, causing new thunderstorms to form.
What is an outflow boundary?
divergence, convergence, and jet streaks. Divergence at the jet level means there is rising air in the atmosphere.
What is measured at 200-300 mb?
Vorticity advection. It is also the best locations to find troughs and ridges. Warm air advections are normally found from rising air, making this very important. Divergence also can happen here. If there's high vorticity and high moisture in one area it likely means clouds.
What is measured at 500 mb?
moisture advection, as well as troughs and ridges. We use it to look for moisture because clouds tend to start around this level (3 kilometers). However, this does not mean there will necessarily be clouds at these moisture levels. It also looks at if dry air moves in as well.
What is measured at 700 mb?
Moisture, isobars, and temperature advection since it can imply rising and moving air.
What is measured at 850 mb?
The Towering Cumulus Stage- a cumulus cloud grows vertically to a height of 20,000 feet. Air within the cloud is dominated by updraft with some turbulent eddies around the edges. Updrafts lift unstable air parcels and air into the cloud, as well as some freezing particles. Raindrops slowly start to grow bigger as particles collide. There is also the entrainment of dry air around edges, evaporating parts of the cloud which makes it look fluffy. The Mature Cumulus Stage- The storm has considerable depth, often reaching 40,000 to 60,000 feet. Strong updrafts and downdrafts coexist, potentially forming tornadoes, large hail, damaging winds, and flash flooding. Early on in this stage the rain gets so heavy the updraft can no longer contain it, and cold rain starts to fall. Due to friction, the rain drags down air forming a cold downdraft. As the downdraft hits the ground, it spreads across the ground and forms a pool of cold air, adnd a gust front. The updraft also starts spreading ice crystals up to the tropopause, causing the top of the cloud to spread like an anvil with an overshooting to the top. The Dissipating Stage- The downdraft cuts off the updraft. The storm no longer has a supply of warm moist air to maintain itself and therefore it dissipates, with maybe a bit of light rain left. The cold pool spreads ahead of the storm as well, cutting off the updraft further, and the rain cools the air to make it stable.
What is the Life Cyclone of a thunderstorm
800 millibars
What is the average air pressure at the center of a tornado?
Bands red, blue, and veggie are combined during the day to measure how it would appear if viewed with human eyes from space. At night, Shortwave Window bands and Clean bands are combined and colorized. The nighttime blue colors represent liquid water clouds such as fog and stratus, while gray to white indicate higher ice clouds. Finally, from a polar orbiting NASA satellite, the nighttime city lights are added.
What is the cycle of the geo-color band like?
Latent heat released during condensation offsets some of the cooling of a rising air parcel, causing the moist adiabatic lapse rate to have a smaller value.
What is the reason for the difference between the values of the Dry Adiabatic Lapse Rate and the Moist Adiabatic Lapse Rate?
adiabatic
What is the term used to describes a process where a parcel of air does not mix with its environment?
Updrafts are continually reforming, with individual thunderstorm updrafts and downdrafts becoming quite strong. This can lead to strong outflow winds and hail. They mainly produce straight-line wind damage.
What is the weather like along a squall line?
While thunderstorms in the cluster will each act as individual thunderstorms, when a cell matures it is carried downstream by an upper level wind, and a new cell will form upwind of the previous cell to take its place.
What makes a multi-cell cluster different from an ordicanry cell?
If it continues to rise or sink when moved upwards or downwards by a small force.
What makes air unstable?
300 mb
What map would you examine to locate the polar jet stream?
May, june, july, and august (70% of all derecho's take place here)
What months does the "warm" derecho season take place?
1) Air mass thunderstorms which occur in the mid-latitudes in summer and at the equator all year long. 2) Thunderstorms associated with mid-latitude cyclone cold fronts or dry lines. This type of thunderstorm often has severe weather associated with it.
What two types of thunderstorms are most common?
fronts and isobars in the atmosphere in a certain area
What type of information does a skew-t chart provide?
Supercell thunderstorms due to their rotating updraft.
What type of thunderstorm normally forms tornadoes?
hurricanes
What type of weather system typically have the strongest horizontal pressure gradients found on earth?
Neutral stability
When an air parcel is moved by forces in the atmosphere to a new position, and it stays in that position once the force is removed.
e. both a and c are correct
When an air parcel reaches the lifting condensation level it will ______ and when it reaches the level of free convection it will ________. Select one: a.change lapse rates from the dry adiabatic lapse rate to the moist adiabatic lapse rate; continue to cool at the moist adiabatic lapse rate. b.become buoyant; form a cloud c.form a cloud; become buoyant d.both a and b are correct e.both a and c are correct
Training Echoes
When an individual cell in a multi-cell cluster moves downstream, but additional cells form and move over the path the previous cell had traveled.
PDS watches are issued when, in the opinion of the forecaster, the likelihood of significant events is boosted by very volatile atmospheric conditions.
When are Particularly Dangerous Situations (PDS) watches issued?
It is issued 12-24 hours in advance to alert the national weather service of high risk or moderate risk storms with a chance of causing massive damage
When is a public severe weather outlook issued?
Zonal Flow
When the air flow is parallel to the latitude lines. Have surface level storm systems, cold fronts, and move very fast from west to east.
Absolute Stability
When the atmosphere returns an air parcel to its original position.
Localized convection
When the ground is heated up unevenly, creating a temperature difference among the area, otherwise known as the albedo effect.
Mesocycle
When the updraft is rotating in a thunderstorm.
Frontal lifting
When there is a difference in density and pressure, causing air to rise over that frontal boundary due to that pressure different creating a barrier from wind to go up
When thunder roars, go indoors and stay there until 30 minutes after the last clap of thunder.
When thunder roars, what is the best course of action to avoid getting struck by lightning?
split window difference
When values for any particles on the dirty channel are subtracted from values of the same location on the clean channel.
Only in warm season events along the north side of the upper atmosphere high pressure ridges, since the jet stream and North Pole mainly move north.
Where and when do progressive derechos take place?
Serial derechos mainly take place in cool season events between the upstream trough and downstream ridge. It can vary since the atmosphere is in constant motion, with constantly cahnging pressure systems.
Where and when do serial derechos normally take place?
The safest location during a thunderstorm is inside a large enclosed structure with plumbing and electrical wiring. These include shopping centers, schools, office buildings, and private residences.
Where are the best places to go to protect yourself from lightning?
Derechos in the United States typically occur along two axes. One axis extends along the "Corn Belt" from the upper Mississippi Valley into the Ohio Valley. The other warm season axis extends from the southern Plains into the mid-Mississippi Valley. In cool seasons, derechos are most likely to occur form eastern texas into the southeastern states.
Where do derechos in the United states normally occur?
fair weather occurs between the ridge and the downwind trough.
Where does fair weather occur?
East
Where does positive vorticity appear in relation to the trough?
between the trough and the downwind (eastward) ridge
Where does the majority of inclement weather occur?
moist air immediately below the cloud base
Which of the following is NOT conducive to downbursts? Select one: a.moist air near the surface b.moist air immediately below the cloud base c.below-freezing temperatures in much of the cloud d.a large environmental lapse rate below the cloud
Since positive originate from the top of the storm the amount of air it must burn through to reach the ground is usually much greater. So it can be even stronger. They can also occur more than 25 miles away from the thunderstorm.
Why are positive lightning strikes more dangerous than negative?
There are massive temperature changes.
Why are pressure gradients so strong near cold fronts?
Thickness values are directly related to air density and temperature, with the colder the air, the denser the air becomes and the distance between two height levels will decrease.
Why are thickness charts used to identify fronts and boundaries between air masses?
There is a large amount of war, most air that comes from the Gulf of Mexico and the Atlantic Ocean
Why are thunderstorms so frequent in the southeastern states of the United States?
A large amount of moist and unstable maritime tropical air masses come from the gulf of mexico, helping the conditions of thunderstorms. These areas are near the rocky mountains, with mountain slopes absorbing more direct solar radiation and becoming warmer, which creates strong updrafts.
Why do the Colorado, Arizona, and New Mexico create a large amount of thunderstorms?
Because density decreases as you go up the atmosphere.
Why does the distance between the pressure lines increase from the bottom of the chart?
Derechos
Widespread, long-lived windstorms associated with a band of rapidly moving showers or thunderstorms. Can produce destruction similar to tornadoes in a relatively straight line.
Rear inflow jet
Wind that punches the backside of the squall line?
Shelf clouds
a cloud which forms as warm and moist air directly rises along the gust front. Normally indicates a gust front.
Roll cloud
a ribbon like cloud that rolls behind the gust front, and normally it forms as the air moves along the gust front and hits the front, that air will then start to move back and roll behind the front, resulting in the cloud.
Tornado
a vortex of rapidly moving air associated with some severe thunderstorms. Descends from a thunderstorm to make contact with the ground
Stable atmosphere
an atmosphere that resists vertical motion. The air does not like to rise on its own. Something has to push the air up on its own. You need a mechanical lifting mechanism, such as an air front, mountain (where the mountain will act as a barrier).
Atmospheric windows
areas where energy passes through the atmosphere, which are used in remote sensing to look into the atmosphere to get information about the weather.
Severe thunderstorms
convective storms with frequent lighting, accompanied by local wind gusts of 97 kilometers per hour, or hail that is 2 centimeters in diameter or larger.
Qualitative forecasts
forecasts which will give specific forecasts describing the events without really focusing on much as numbers.
Orographic lifting
generally when air is lifted by mountains that have to go over it
Cavected available potential energy (CAPE)
indicates how unstable the atmosphere is. As it gets bigger, it indicates that the atmosphere is unstable and how strong the updraft could be in thunderstorms.
Convective inhibition
inhibits a parcel from rising, where the air parcel is then colder than the environment, making it stable.
Isoheigts
lines of equal height which represent the altitude at which pressure takes place at. Also known as contours.
Temperature lines
lines that are drawn at 45 degree angles with temperature values that increase from the upper left to the lower right corner of the chart.
Isobar
lines that represent the areas of equal pressure along the line.
Electromagnetic weaves.
obtain information about the atmosphere through remote sensing, where we can learn about objects without being in contact with them. Do not need molecules to travel unlike sound waves.
Stratisform rain
rain that forms in much weaker vertical motion with a slanted updraft.
Blocking high
responsible for major heat waves. Any precipitation is usually shunted around the periphery of the high-pressure area. High pressure causes the air to sink, compressing the warm air in the lower atmosphere and trapping heat, creating heat waves. Skies are normally clear.
Adiabatic
the change in temperature of an air parcel only because the air parcel is expanding or contracting. SO as air rises, pressure decreases and the air parcel expands, thus also cooling.
Gust front
the leading edge of a cold pool that acts similarly to a cold front. It forms from the cold downdraft air from a thunderstorm, rather than air mass changes. It acts as a boundary with a temperature difference, with air being cold around it due to the rain being colder than the environment.
Mixing Ratio
the mass of water vapor compared with the mass of dry air. It is shown as grams per kilogram.
Infrared imagery
uses temperature, such as how much radiation is being emitted off the ground back into space. It basically measures longwave radiation that we can match to specific temperatures. Clouds will also absorb the sun's energy, before releasing it back into space.
Blocking Patterns
when centers of high pressure and low pressure preside over a region where they prevent other weather systems from moving through, forming the weather systems around it.
Bookend vortex
when the bow echo curls more around the edge. This is caused by the coriolis force bending it. It can also happen on the opposite end. These areas can form tornadoes due to rotation
