CHAPTER 6: SEVERE WEATHER AND STORM SYSTEMS Flashcards
First documented F5 tornado in Canada
Eli MB
How long do microscale atmospheric systems last?
Only a few hours
How long do synoptic and global atmospheric systems last?
Weeks-MONTHS
A direct relationship between ___ and ___ of atmospheric systems.
Size and Duration
Storm systems derive energy from (2)
Solar heating and condensation
Typical time of day of tornados
Late afternoon
Typical duration of tornados
5 mins
Typical time of year for tornados
April-June
Define Thunderstorms
Cumulonimbus cloud that produces lightning and thunder
Where are thunderstorms most frequent?
Over tropics
How many thunderstorms worldwide each year?
16 million, 2000 in progress at once
Where do thunderstorms typically take place in USA and Canada
Great Plains
Define air masses
Large body of air with fairly uniform temperature and moisture characteristics
Air masses are classified based on….
source area
Define Source area
extensive land or ocean surfaces over which an air mass derives its temperature and moisture characterics
Latitudinal position of air masses alters the
Temperature
Underlying surfaces of air masses alters the…
moisture
2 possible underlying surfaces of air masses
C=continental(dry)
m=maritime (wet)
5 possible latitudinal positions of air masses
A= ARCTIC AA= ANTARCTICA P=POLAR T= TROPICAL E= EQUATORIAL
(ACRONYM… PETA-AA)
cA airmass is…
Polar high, very cold and dry
cP airmass is…
polar high, cold, dryu
mP airmass is…
polar high and sub polar low, humid
cT airmass is…
subtropical high, hot/dry
mT airmass is….
ITCZ… subtropical high/warm, humid
3 types of thunderstorms
- Single-cell
- Multicell
- supercell
2 most important factors that determine thunderstorm type…
Atmospheric humidity and wind shear
How intense are single-cell thunderstorms?
mild and short-lived
Where do single-cell thunderstorms form?
within mT air masses (weak wind shear)
When do single-cell thunderstorms typically develop?
Late afternoon
Single-cell thunderstorms typically experience a predictable sequence of….
growth, maturation, and dissipation
Multicell thunderstorms form under what wind shear?
moderate wind shear
Multicell thunderstorms form along… (where in terms of air masses)
Along the fronts of air masses
how are multiicell thunderstorms arranged?
In clusters or squall lines
What is a squall line?
line of multicellular thunderstorm cells that typically form along a cold front on a midlatitude cyclone
What is a gust front (squall line)
Cold surge of air at ground level
What is a derecho?
a gust front in excess of 93km/h over a 400km area
Where is the forward flank in a multicellular thunderstorm?
Hot, humid side
Rear flank of a multicellular thunderstorm
cold, dry side
to be classified as a severe thunderstorms they need to have 1 or more of what 3 what conditions…
- produce hail 2.54 cm in diameter
- a tornado
- wind gusts of 93km/h or greater
Supercell thunderstorms form over land that is…
humid and strong wind shear