A single or cluster of cumulonimbus clouds that produce lightning and thunder. May contain heavy rains or even gusty winds
Scattered summertime thunderstorms that tend to develop in warm, maritime tropical air masses away from weather fronts (in FL)
Does a thunderstorm produce hail?
Yes - sometimes. Cumulonimbus clouds are the only ones capable of producing hail
Cumulus stage of a thunderstorm
As humid air rises, it cools and some of its water vapor condenses into a single cumulus cloud or cluster of clouds
True or false: During the Mature stage is when large amounts of latent heat is released - keeping the inside of the cloud warmer than the surrounding air
FALSE! This happens in the Cumulus stage
True or False: A thunderstorm is most intense in its Cumulus stage?
FALSE - its most intense in its Mature stage.
At which stage does the cold air take on its anvil shape where the cloud itself can reach altitudes of over 40K feet?
Ordinary Cell Thunderstorm
Tend to form in a region where there is limited wind shear - that is where the wind speed and wind direction do not abruptly change with increasing height above the surface
True or false: The tilt of the anvil is an indication of the direction of which way the storm moves
3rd and final stage of a thunderstorm. Downdrafts occur - light precipitation now falls, most of the cloud particles in the lower half of the storm have evaporated.
Capable of producing large hail (3/4"), strong gusty winds (50mph or more), flash floods and tornadoes.
The updrafts may be strong, up to ______ knots, and precipitation size particles do not have time to form
Why does the cooling effect only last a short while after the storm has dissipated?
After a storm, the air temp usually rises; and as the moisture from the rainfall evaporates into the air, the humidity increases - sometimes to a level where it feels even more oppressive after the storm than before.
Thunderstorms that contain a number of cells, each in a different stage of development
If the updrafts are extremely strong, they may do this well in to a stable stratosphere -possibly to more than 60K feet! Hail also can grow to very large sizes.
What is the main difference between a roll cloud and a funnel cloud?
Roll clouds spin horizontally & Funnel clouds spin vertically
boundary that separates the cold downdraft from the warm surface. Literally looks like a cold front, to an observer on the ground
With the passage of a gust front, surface pressure may rise rapidly and create a small area of high pressure called
As warm, moist air rises along the forward edge of the gust front, this may form; AKA barber pole cloud
A surface boundary formed by the horizontal spreading of cool air that originated inside a thunderstorm
strong localized winds that hit the ground and are spread out horizontally (like water from your faucet hitting the sink)
Microbursts are often accompanied with ____ _____, which is a rapid change in wind speed OR wind direction
True or False: Microbursts can produce only isolated showers, in which they may or may not contain thunder?
single, violently rotating updraft, enormous storms that can maintain themselves for hours. 90 knot winds, grapefruit size hail and many tornadoes MAY form - mostly in the springtime.
forms as a line of multicell thunderstorms. sometimes you can see them right along a cold front or in the warm air some 100-300km ahead of it
These _______________________ are the most severe type of squall line
pre-frontal squall line thunderstorms
Ordinary squall lines
Squall lines that exhibit weaker updrafts and downdrafts tend to be more shallow than pre- frontal squall lines and usually have shorter life spans.
the shape of a squall line that often produces damaging surface winds near the center of the bow. Sometimes the left (northern) end of the bow will develop into cyclonic rotation and produce a tornado
Flash floods often occur with ....
spring snow melt, tropical storms, downburst from a strong thunderstorm
A large convective weather system that contains a number of individual thunderstorms that will grow in size is called a
MMC - mesoscale convective complex
True or false: the rotating updraft associated with the mesocyclone is so strong that precipitation cannot fall thru it
True - this produces a rain free base beneath this updraft
rotating cloud that may descend from the base of the storm if low-level humid air is drawn into the updraft.
Why does the South Eastern portions of the country have more annual thunderstorms, but the Western Great Plains have more hail?
Because its colder there - hail needs cold air / front
The average number of days each year on which thunderstorms are observed throughout the US
Most in FL - lessening up as you move north west
The average number of days each year on which hail is observed throughout the US
mostly in CO, NM, NV - dissipates in a circle moving in all directions
extreme heat causes air to expand explosively, initiating a shockwave that becomes a booming sound wave
Can lightning occur without thunder?
No - there is actually thunder, but the atmosphere refracts (bends) and attenuates the sound waves.
True or false: for lightning to occur, separate regions containing opposite electrical charges must exist within a cumulonimbus cloud
True or false: When falling precipitation collides with smaller particles, the larger precipitation particles become negatively charged and the smaller particles, positively charged
A Lightning stroke involves a ______, which is an initial charge of electrons that proceeds intermittently toward the ground in a series of 'steps' in a cloud to ground lightning strike
the downward flow of electrons establishes the bright channel of upward propagating current. This all happens in 1/10,000 of a second.
There is a subsequent leader called a ____ that proceeds from the cloud along the same channel as the original stepped leader - about 4/100ths of a second later
Typically lightning will have ____ leaders - each followed by a return stroke. All of this happening in less than a second
most common - dart leader moving towards the ground which deviates from the original path by the stepped leader
occurs when the lightning channel breaks up or appears to break up. exact cause is not knows, but stroke may be partially obscured by clouds or falling rain
when lightning enters sandy soil, high temperatures of the stroke may fuse sand particles together forming these tubes
on a radar-type map of lightning - red and blue hits are shown. which are old, which are new?
blue - old; red - new
rapidly rotating winds that blow around a small area of intense low pressure with a circulation that reaches the ground
The size of tornadoes are between 300 - 2000 ft in diameter and tend to move ___ to ___ at around ___ knots due to the steering of SW winds (normally)
SW to NE at around 20-40
scale for classifying tornadoes according to their rotational wind speed - cannot classify until assessing damage afterwards
MOST tornadoes are in the line of F_ and F_ - maybe one per year will reach F_
F0 - F1 - are most - once a year it can be F5
causes the most damage - have smaller whirls that rotate within them - exceeding 180 knots
Most tornadoes in US occur in the 'tornado belt' of the Central Plains - stretches from TX to NE
Tornado is moving from SW to NE - the strongest winds are 90 degrees to the ____ of movement of the storm
bounded weak echo region (BWER)
the region inside the supercell where radar is unable to detect precipitation
while precipitation is drawn into a cyclonic spiral around the mesocyclone, the rotating precipitation may unveil itself in the shape of a hook called