Thunderstorms Flashcards
convective storm that produces lightning and thunder characterized by strong up and down movement within the cloud
Thunderstorm
Thunderstorms form, when
humid air rises in an unstable environment
Usually 2 lifting mechanisms
discharge of electricity between thunderstorm cloud and ground or between two thunderstorm clouds
Lightning
most frequent 80% of all lightning
Cloud to cloud
Less frequent 20% of all lightning
Cloud to ground
conditions to get lightning to form
Clouds must extend above freezing level
Clouds must produce precipitation
Charges must separate within the cloud
separation of charges
Lighter particles bring positive charge to type of cloud
Heavier particles bring negative charge the base of cloud
Stage one
step leader forms
Negative charges start to step down from cloud toward positively charge surface
Step two
streamer forms
Positive charges at surface start to stretch upward toward cloud
Stage three
return stroke
Negative charges make contact with a positive charge is near the ground
Bright flash starts from surface up
Negative charges, drained from base of cloud
Stage four
dart leader forms
negative charges start to step down from cloud toward positively charge surface, using the same channel as the step leader
stage five
return stroke
Negative charges make contact with a positive charge is near the ground
Bright flash starts from surface up
Negative charges, drained from base of cloud
Stage six
total discharge takes around — seconds, and consists of multiple return strokes
0.2 seconds.
sound waves produced when super heated air from lightning expands explosively
Speed of light much faster than speed of sound
For every five seconds between lightning and thunder, 1 mile from storm
Thunder
self extinguishing storms caused by unequal heating of service
mT air masses
Short-lived
Typical and warm, humid summer days
Air mass thunderstorms
self propagating storms caused by frontal lifting
Long lasting
Produce high winds, hell, flash, floods, and or tornadoes
10% of all US thundersto
Severe thunderstorms
three main stages of an air mass thunderstorm
Cumulus
mature
Dissipating
updrafts, dominate cloud grows inside, due to continuous supply of warm, moist and latent heat released as air rises and cools adiabeticaly
no precipitation
Cumulus stage
updrafts and downdrafts present
Cloud grows to top of troposphere
precipitation, initiates, downdraft
Most intense phase of thunderstorm
Mature stage
down draft dominate
Entrainment
Moisture supply is cut off, and cloud starts to disappear
Precipitation, weakens
Dissipating stage
Bringing in dry air from surrounding atmosphere
Entrainment
In order to be classified as severe thunderstorm have to meet one of the criteria
Winds above 58 mph
Hail, 0.75 inches.
Tornado produced
tilt it up and down draft support each other
Form in areas with strong wind shear
Severe thunderstorms
differing wind speeds, or directions at different heights in the atmosphere
Windshear
dance cool air from downdraft spreads beneath cumulonimbus cloud
Gust front
Severe thunderstorms
leading edge of outflow and downdraft acts like front, lifting, warm air ahead of thunderstorm
gust front
three main types of severe thunderstorm
supercell
Squall line
MCC
Single powerful cell containing just one updraft
Supercell
Temperature inversions, can aid production of supercells buy inhibiting, smaller storms
Convention prevented by inversion
Supercell
narrow band of individual thunderstorms
Forms and warm sector of mid latitude, cyclone ahead of cold front due to dryline
Squall lines
Narrow zone of abrupt humidity change, where mT and cT air converge in the warm sector of mid latitude cyclone
Dryline
Group of individuals, thunderstorms organized into an oval shaped cluster
Frequently found in great plains in migrate east with upper air Winds
MCC
Mesoscale convective complexes
downdraft from each cell ask to create new cell northern most cells, die out while new cells created a long, southern boundary
Mesoscale convective complexes
Area of strong straight line winds in association with a severe thunderstorm
Capable of producing as much damage does a tornado
Affect at least 240 miles worth of surface area
Derecho
Lightning safety
Lightning can strike up to 10 miles from thunderstorm
Safest place inside
Stay away from tall objects
