Final Meteorology Test
nonsupercell tornadoes
do not occur in association with a pre-existing wall cloud (or a mid-level mesocyclone) of a supercell
HP (high precipitation) supercell
dominated by heavy precipitation, strong downdrafts, and large hail
superior mirage
object appears to be higher than it actually is -images will always be displaced towards the warmer, less dense air
many hurricanes form off what coast
off the coast of mexico over the north Pacific (usually spawns 9 per year)
along the gulf and atlantic coasts...
on average about 5 hurricanes make land fall every 3 years, two of which are major hurricanes with winds in excess of 95 knots (110 mi/hr)
what counts as severe thunderstorm?
one inch diameter hail and/or wind gust 50 knots or greater and overshooting
most tornadoes only last this long and have a path of...
only last a few minutes and have an average path of 4 miles but some have remained on the ground for as long as 7 hours
swells surge...
out from storm
numerical weather prediction
the routine daily forecasting of weather by the computer using mathematical equations
supercell tornadoes
tornadoes that form with supercell thunderstorms (that have single rotating updraft that can exist for hours)
much to be improved with hurricane prediction, true or false
true
no widespread agreement to how hurricanes form: t or f
true
rainbow moves with you and you don't see the same rainbow as someone next to you
true
thunderstorm stages of development
1. cumulus 2. growing (sometimes the cumulus and growing stages are combined into one stage called the cumulus stage) 3. mature
tornado safety tips
-go to basement of the house of an inner room with no windows if it has no basement -leave mobile homes...they are death traps - don't try to out run it in a car- find a ditch -don't open windows of the house
safety measures pertaining to thunderstorms
-stay indoors if possible -cars are relatively safe locations -stay off of phones (cell and wireless okay from base unit) -stay away from plumbing (a lot is metal), metal fences, tall and isolated trees -crouch low if in an open field more people die statistically from lightning than hurricanes
majority of tornadoes are relatively weak with wind speeds
...less than about 110 knots (115 mi/hr) ...yearly average deaths is less than 100
development of a hurricane
1. Tropical disturbance- cluster of thunderstorms with an *organized* circulation/wind field 2. Tropical depression- (sustained) winds (not gusts) increase to between 20 and 34 knots 3. Tropical storm- winds increase to between 35 and 64 knots. Storm is given a name at this point 4. Hurricane- winds exceed 64 knots
mechanisms for development of a thunderstorm
1. air mass 2. orographic (mountains, convergence over florida)
development from birth-> maturity-> decay
1. cumulus stage/growth stage- humid air cools and condenses into a cumulus cloud or cluster cloud continues to grow in unstable atmosphere. when drier air from around the cloud is being drawn into it-> entrainment air descends as a downdraft 2. downdraft marks... mature stage: thunderstorm is moist intense, takes on anvil shape. may extend upward to more than 12 km (40,000 ft) updrafts and downdrafts strongest in the middle of the cloud gust front- the surface boundary that separates the advancing cooler air from the surrounding warmer 3. dissipating stage- occurs when the updrafts weaken as the gust front moves away from the storm and no longer enhances the updrafts -a single thunderstorm may go through its three stages in one hour or less *updraft gives way to downdraft— then storm collapses on itself*
stages of tornadoes
1. dust-whirl stage 2. mature stage 3. decay stage
theory of how charges come about in clouds
1. electrification of clouds: hailstones/ ice crystal droplets collisions result in net transfer of positive ions from the warmer object to the colder object 2. has to do with updrafts mixing different charges of precipitation
probability of precipitation revolves around
1. numerical weather prediction 2. watches/warnings 3. private vs. public 4. AWIPS- advanced weather interactive processing system
Methods of forecasting
1. persistence: future weather will be the same as present weather 2. steady-state/trend, nowcasting 3. analogue: conditions on the weather charts strongly resemble features that produced certain weather conditions sometime in the past 4. climatology forecast: a forecast based on climatology (average weather) 5. ensemble forecasting: averaging several models or runs of the same model 6. probability of precipitation
triggers to start air moving upward
1. random, turbulent eddies that lift small bubbles of air 2. unequal heating at the surface 3. the effect of terrain (such as small hills) or the lifting of air along shallow boundaries of converging surface winds 4. diverging upper-level winds, coupled with converging surface winds and rising air 5. large-scale uplift along mountain barriers or gently rising terrain 6. warm air rising along a frontal zone. usually, several of these work together
the process of lightning
1. stepped leader: invisible, creates channel thats conducive. starts from the cloud to the ground usually 2. positive charges on the ground 3. return stroke: from ground to the cloud
types of thunderstorms
1. super cell 2. squall line: strung out thunderstorms along a line. does not need to be uniform 3. MCCs (mesoscale convective system) or MCSs 4. slow moving storms and flash floods
stages
1. tropical disturbance becomes a TROPICAL DEPRESSION (20-34 knots. 23-39 mi/hr) 2. TROPICAL STORM (35-64 knots/40-74 mi/hr) 3. Hurricane= 64 knots (74 mi/hr)
lightning can occur
1. within cloud (sometimes called sheet lightning) 2. cloud-to-cloud 3. cloud-to-ground 4. cloud-to-air (terminates in air) (stroke can heat the air to 30,000 (54,000F) creating a shock wave (thunder)
65% of all hurricanes form between what latitudes?
10 and 20 degrees latitude. none from 5s to 5n
sound of thunder travels at only about...
1100 ft./sec
perhaps less than what percent of supercells produce tornadoes?
15% -more likely when they interact with a pre=existing boundary, such as an old gust front (outflow boundary)
saffir-simpson damage potential scale
1: 74-95 mph, 64-82 knots. Pressure same or greater than 980 All the way down to 5 5: winds exceed 155 mi/hr or 135 knots. Pressure less than 920
*forecasts made between 12-24 hours are usually quite accurate
2-5 fairly good beyond 7 days-accuracy falls rapidly
the diameter of most tornadoes is about
300 to 2,000 ft. but some are as small as just a few meters and others nearly a mile wide
currently, a forecast models predict the weather reasonably well...
4-6 days into the future; models tend to do a better job of predicting temperature and jet stream patterns than predicting precipitation
it is estimated that how many thunderstorms occur daily giving a yearly total of about ____ annually worldwide
40,000 daily 14,000,000 annually
yearly amount of hurricanes born over the tropical North Atlantic
6
tornadoes sometimes exceed
70 knots (80 mi/hr)
ocean waters of about __ or higher are required for development
80F
omega high
=blocking high. one that tends to persist in the same geographic location for many days
new, experimental doppler system
DOPPER 4 DAR. uses a light beam to measure the change in frequency of falling precipitation, cloud particles and dust
what are tornadoes measured on
Fujita scale: F0-weakest— F5 strongest. -about 2/3 of all tornadoes are F0 or F1 and only about 2% are F4 or F5 but 2/3 of all deaths are from those -since, a new enhanced scale has been developed but is quite complicated. called the EF scale
GCMs
General circulation models- are doing a far better job at predicting large-scale atmospheric behavior than did the earlier models
hurricane season
May 15-November 30 in Northeast Pacific June 1-November 30 in North Atlantic peaks in September
surface pressure of storm
Outside of storm has the highest pressure, inside has lowest Worst conditions around the periphery of the center of the storm The center of low pressure is called the eye and is characterized by clear skies and calm winds The average diameter of they eye is about 15 miles- but varies considerably In general, the smaller the eye, the more intense the hurricane Just outside the eye is the area of strongest winds and most intense thunderstorms and is called the eye wall Curved strips of thunderstorms are called curved bands
hurricanes have no fronts -T or F
T
soundings
a 2 dimensional vertical profile of temp, dew point and winds. helpful for short-range forecasts
meteogram
a chart that shows how one or more weather variables has changed at a station over a given period of time
tornadoes require what type of atmosphere?
a conditionally unstable atmosphere
corona discharge
a continuous supply of sparks, known as st. elm's fire. means lightning flash may occur in near future
lightning
a discharge of electricity, a giant spark which usually occurs in mature thunderstorms. may travel within a cloud, from one cloud to another, from a cloud to the surrounding air, or from a cloud to the ground majority happens within a cloud can heat the air to 30,000 degrees C (54,000 F)— five times hotter than the surface of the sun
microburst
a downburst with winds extending only 4 km or less-may induce straight line winds as high as 140 knots (161 mi/hr) or more
mesoscale convective complexes
a large convective weather system. can be as much as 1000 times larger in area than an individual, ordinary cell thunderstorm. individual thunderstorms work together to generate a long-lasting (more than 6 hours) weather system that often exists for periods exceeding 12 hours. tend to form during summer
tornado
a rapidly rotating column of air extending down from a cumuliform cloud that blows around a small area of intense low pressure with a circulation that reaches the ground. can assume a variety of shapes and forms
thunder
a shock wave that becomes a booming sound wave as a result of air expanding explosively from extreme heating of lightning
what signals a squall line?
a sudden wind gust followed immediately by a heavy downpour
derecho
a windstorm where straight-line winds, gusting to more than 50 knots (58 mi/hr) persist along a path at least 400 km (250 mi) long -usually form in early evening and last throughout the night
ASOS system
automated surface observing systems. operated at selected airports and other sites in US. designed to provide nearly continuous information about wind, temperature, pressure, cloud-base height, and runway visibility at various airports
most tornadoes only last
about a few minutes and move an average path length of 7 km (4 mi)
eyewall
adjacent to the eye, a ring of intense thunderstorms that whirl around the storm's center and may extend upward to almost 18 km (59,000 ft) above sea level. it is here that we find the heaviest precipitation and the strongest winds
AWIPS
advanced weather interactive processing system. the communication system in use today. AWIPS II adopted in 2013
convective available potential energy (CAPE)
amount of instability in the atmosphere represented by this. a measure of how much energy is available to produce strong updrafts
storm surge
an abnormal rise of several meters in the ocean level... which inundates low-lying areas— particularly damaging
supercell
an intense long-lasting thunderstorm with a single violently rotating updraft. capable of producing updrafts greater than 90 knots. top of storm may extend to as high as 18 km (60,000 ft) above the surface with width exceeding 40 km (25 mi) largest hail observed from these
hurricane
an intense storm of tropical origin with sustained winds of at least 64 knots (74 mi/hr) and with considerably higher gusts, which forms over the warm northern Atlantic and eastern North Pacific oceans. In North Pacific called a typhoon, in India a cyclone and in Australia, a tropical cyclone.
advisories
are issues to inform the public of less hazardous conditions caused by wind, dust, fog, snow, sleet or freezing rain
negative cloud-to-ground lightning
base of cloud is negatively charged and ground is positively charged 90% of all cloud-to-ground lightning is negative, though positive can happen
climatology forecast
based on the climate of a particular region
when is the most frequent times for tornadoes?
between 4 and 6 PM
bow echo
bow-shaped squall line
iridescence
bright areas produced by diffraction (the bending of light as it passes around objects)
why do computer models lack
cannot adequately interpret many of the factors that influence surface weather, such as the interactions of water, ice, surface friction and local terrain on weather systems
saffir-simpson hurricane wind scale
category 1 (weakest) to category 5 (strongest). major hurricanes classifies as category 3 and above
where is most susceptible to tornadoes?
central plains. frequency is highest during the spring and lowest during the winter when the warm surface air is normally absent. 70% from march to july. May usually has greatest (9 per day) most violent occur in April
why do forecasts go wrong?
computer models have inherent flaws, majority of models are not global in their coverage — errors are able to creep in along the model's boundaries
multi-vortex tornadoes
contain smaller winds that rotate within them. smaller winds called such low vortices (only about 10 m or 30 ft. in diameter but cause much damage)
hurricanes formation continued..
convergence of surface winds usually wind responsible comes from Africa strong TRADE WIND INVERSION may create a hurricane do not form where upper-level winds are strong (el niño)
stepped leader
covers 50-100 meters, approaches ground. then there's a return stroke after
heat lightning
distant lightning not seen but heard
hurricanes that form over the warm tropical north pacific and northatlantic are steered by
easterly winds and move west or north westward at about 10 knots for a week or so...most north atlantic hurricanes swing away from land, parallel to the coastline to of US. perhaps 3 a year go inland
when a hurricane is approaching from the south, it's highest winds are usually on its ___ side
eastern/right
roll clouds
elongated ominous-looking clouds that form behind the gust front
weather forecasting
entails predicting how the present state of the atmosphere will change
straight line winds
exceeding 60 miles per hour behind a strong gust front. is formed by strong gust front
extended forecast
extends beyond 3 days
long-range forecast
extends beyond about 8 days
medium-range forecast
extends from about 3-8 days (192 hours) into the future. almost entirely based on computer-derived products
average sizes of certain weather
extra-tropical cyclone is 1,000-10,000 km tornado is about 1/4 km hurricane is about 800 km
majority of hurricane related deaths are caused by...
flooding
flash floods
floods that develop rapidly with little or no advance warning. often results when thunderstorms stall or move very slowly
nowcast
forecast for up to a few hours (usually not more than 6 hours). usually uses surface observations, satellite imagery and Doppler radar
rapid refresh
forecast model, has a grid spacing as low as 3 km. can actually incorporate radar information and simulate how showers and thunderstorms might evolve
types of lightning
forked lightning, ribbon, bead, ball, and sheet lightning
pre-frontal squall line thunderstorms
form directly along a cold front and extend for hundreds of kilometers, or may form in the warm air 100-300 km out ahead of the cold front -> of the middle latitudes, represent the largest and most severe type of squall line
hurricane formation
form over tropical waters where the winds are light, the humidity is high in a deep layer extending up through the troposphere and the surface water temp is warm, typically 26.5 degrees C (80 F) or greater over a vast area - usually prevail over the tropical and subtropical North Atlantic and North Pacific Oceans during the summer and early fall
where does energy come from?
from the direct transfer of sensible heat and latent heat from the warm ocean surface...the warmer the ocean surface, the lower the minimum pressure of the storm and the higher its winds
tornadoes that do not touch the ground
funnel clouds
outlooks
general trends in products
two main purposes of cloud seeding
hail suppression and rain enhancement. silver iodide, dry ice, conflicting statistics as to the effectiveness of the procedure
up until mid 1950s, weather forecasts were plotted by
hand/analyzed by individuals.. final chart was called an analysis
tropical waves
have wavelengths of 2500 km (1550 m) and travel from east to west at speeds between 10 and 20 knots. main area of showers form BEHIND the trough
what is dry lightning
high based, rainless
mesohigh
the relatively small, shallow area of high pressure. raises risk of high winds
lightning direction finder
how lightning strokes directed by detecting radio waves are produced
river floods
if thunderstorms bring heavy rain for days or weeks. major river system rises slowly but floods a large area
super typhoon
in western pacific, a typhoon with sustained winds of at least 100 knots (115 mi/hr) at the lower end of the speed range in category 3
watch
indicates that atmosphere conditions favor hazardous weather occurring over a particular region during a specified time period, but the actual location and time of the occurrence is uncertain
warning
indicates that hazardous weather is either imminent or actually occurring within the specified forecast area
critical angle
is 48 degrees. when light hits the backside of a raindrop in such an angle that it is reflected within the drop... subsequently is internally reflected toward our eyes
tornado warning
issued when tornado is spotted either visually or on radar
NOAA...
issues seasonal outlooks every month
states and tornadoes
kansas has the greatest number per square mile. Texas has the greatest number in all. EVERY state has had a tornado. may be rare but they happen
when are tornadoes most frequent?
late afternoon: 4-6 PM
up until 2005, the annual death toll from hurricanes in the US, over a span of about 30 years, averaged...
less than 50 persons
how thin is lightning
less than an inch across
red sprite/blue jet
lightning shoots upwards in a flash
cloud iridescence
like a rainbow. is reflection through ice crystals
dart leader
like stepped leader but proceeds downward more quickly because electrical resistance of the path is now lower
squall line
line of thunderstorms— multicell thunderstorms may form as this
statistical forecasts
made routinely of weather elements based on the past performance of computer models
what does "the chance of rain is 60%" mean?
means that there is a 60% chance that any random place in the forecast area, such as your home, will receive measurable rainfall
thunderstorm
merely a storm containing lightning and thunder, are convective storms that form with rising air. often begins w/ warm, moist air rising in a conditionally unstable environment
sonic boom
mistaken from thunder. when an aircraft exceeds the speed of sound at the altitude of which it is flying
hurricane warning
more certain that storm will arrive
what's the average number of tornadoes per year
more than 1,000. has more than doubled since 1950 because of more reporting techniques
tornado formation
most often tornadoes form with supercell thunderstorms in an environment with strong vertical wind shear
NCED
national center for environmental prediction
NWS
national weather service
ekman transport
net transport of water to the right of the surface wind in the Northern Hemisphere
polarimetric radar
new, transmits BOTH a horizontal and vertical radar pulse-> used to distinguish between rain and hail. can improve flash flood warnings
NEXRAD
next generation weather radar
heat lightning
no such thing. is only a thunderstorm you are too far away to hear the lightning from
why are cars safest place in thunderstorm?
not because of tires, but because electricity... because it seeks the path of least resistance...this goes around the car to the ground
steady-state/trend forecast
principle that surface weather systems tend to move in the same direction and at approximately the same speed as they have been moving
classic supercells
produce heavy rain, large hail, high surface winds and the majority of tornadoes
short-range forecasts
range from about 6 hours to a few days (generally up to 3 days or 72 hours). may incorporate variety of techniques
rear-flank inflow jet
rather narrow band of fast-flowing air
funnel cloud
refers to a visible funnel that does not touch the ground. only about 30% of funnel clouds become active tornadoes
primary rainbow
reflection of raindrops
eye
relatively clear area of the center is this. winds are light and surface area is low. around 955 mb (28.20 in)
the analogue method
relies on the fact that existing features on a weather chart or series of charts may strongly resemble features that produced certain weather conditions some time in the past problem: weather conditions never exactly the same. predicting the weather by weather types employs this method
ensemble forecasting
response to environment's chaotic nature— based on running several forecast models or different versions of a single model to reflect the errors inherent in the measurements— improves short and medium range forecasts -if prog match each other fairly well, the forecast is considered robust -the less agreement among the progs/the model runs, the less predictable the weather
if prog or model runs match each other fairly well, the forecast is considered
robust
mesocyclone
rotating air column, usually 5-10 kilometers across
waterspouts
rotating columns of air that are connected to a cumuliform cloud over a large body of water. can be a tornado that travelled over water. does not draw water up into its core
Tornado Alley:
runs from Texas to Nebraska... frequent tornadoes
for lightning to occur...
separate regions containing opposite electrical charges must exist within a cumulonimbus cloud
hook echo
shape of precipitation in the formation of a tornado
interactive forecast preparation system
software component of AWIPS that allows forecasters to look at the daily predictions of weather elements, such as temp and dew point in a gridded format with spacing as small as 2km
most destructive and extreme winds will be on the tornado's what side
southeastern side
grid points
spaced from 100 km to as low as 0.5 km apart. models w/ large spacing—smaller storms can be missed
estimating distance of lightning
start counting the seconds from the lightning to the time you hear thunder and then divide by 5
severe thunderstorms
storms that produce at least one of the following: large hail w/ a diameter of at least one inch, surface wind of at least 50 knots (58 mi/hr) or a tornado
when it comes to hurricanes, forecasters typically analyze what that depict wind flow
stream lines: sometimes are disturbed by weak trough or lough pressure called a tropical wave or easterly wave
heat bursts
sudden warm downbursts (others are usually cool)
ordinary cell/air mass thunderstorms
tend to form in warm, humid air masses away from significant weather fronts -tend to form where there is limited vertical wind shear (where the wind speed and/or wind direction do not abruptly change w/ increasing height above the surface) -usually form along shallow zones where surface winds converge
LP (low precipitation) supercell
tend to produce little rain— still capable of producing large hail and tornadoes visible as a bell- shaped tower with a corkscrew-like pattern along its sides
Eyewall replacement
the dissipation of the original eyewall and the formation of a new one further out
resolution
the distance b/w grid points. a model w/ higher resolution alone does not necessarily mean the model is more accurate
persistence forecast
the easiest to make. simply a prediction that future weather will be the same as present weather
prognastic chart/prog
the final forecast chart representing the atmosphere at a specified future time
tornadogenesis
the formation of a tornado- when the rear flank downdraft strikes the ground and interacts with the forward flank downdraft beneath the mesocyclone this may occur
the greater the rate of temperature change,
the greater the light rays are bent
forecasting larger scale weather events several days in advance is far more accurate than forecasting
the precise evolution and movement of small-scale, short-lived weather systems
bounded weak echo region (BWER)
the region inside the supercell where radar is unable to detect precipitation
the first sign that a supercell is about to give birth to a tornado
the sight of rotating clouds at the base of the storm
9/10 people who die in a hurricane are killed by what?
the storm surge and flooding
if the storm has a well-defined eye and a dense cirrus cloud shield when it reaches hurricane strength,
the storm will most likely continue to strengthen
cell-wide storm tilts
the updraft actually rides up over the downdraft
most of what we know about tornadoes comes from
the use of Doppler Radar (wave pulses sen out, energy strikes an object and a small fraction is scattered back to the antenna)—can peer into a server storm and reveal its winds on doppler radar, hook echo (hook shaped appendage) usually signals a mesocyclone or tornado on Doppler Radar
hurricanes are not the largest storms nor the strongest, but...
they are the most destructive
hurricanes will quickly weaken if..
they move over land or colder water
hurricanes weaken rapidly when...
they travel over cold water and lose their heat source
multicell thunderstorms
thunderstorms that contain a number of cells, each in a different stage of development. tend to form in a region of moderate to strong vertical and speed shear
positive lightning has potential
to cause more damage because it generates a much higher current level and its flash lasts longer than negative lightning
gustnadoes
tornadoes that form along a gust front. typically form as a result of strongly converging winds along the edge of a rear-flank or forward downdraft
secondary rainbow
two internal reflections, lies above or outside the primary, fainter than primary, reverse color order from primary
hurricane watch
typically 24-48 hours before storm arrives
sprites
up in the clouds/sky: large scale electrical discharges
what helps provide a birds eye view of the storm
visible, infraared, and enhanced enfrared satellite images...and aircraft/ dropsondes (that are dropped into the storm). bathythermograph measures temp
lands points
weak, short lived tornadoes that occur with rapidly building cumulus congestus clouds look similar to waterspouts, usually form over eastern colorado
mesocale convective system
what squall lines are driven by. convective processes of middle scale in size
tornado outbreak
when a large # of tornadoes (typically 6 or more) form over a particular region (families of tornadoes)
inferior mirages
when air near the ground is much warmer than the air above. object may look lower and/or inverted
dry lightning
when cloud-ground lightning occurs thunderstorms that do not produce rain
overshooting top
when convection is strong and the updraft intense, rising air intrudes well into the stable atmosphere
rainbows occur
when rain is falling in one part of the sky while the sun is shining in another
superior mirage
when the air near the ground is much colder than the air above. object looks shifted upward
when are storms given names
when they reach tropical storm strength... alphabetical in order. names are recycled every 6 years
tornado watch
when tornadoes are likely to form during the next few hours
inferior mirage
where an object is misplaced lower than it actually is
macroburst
winds extending more than 4 kilometers
iridescence is seen most often
within 20 degrees of the sun and is often associated with thin clouds such as cirrocumulus and altocumulus
majority of lightning happens
within the cloud
WMO
world meteorology organization- responsible for the international exchange of weather data, includes more than its nations
