Transcript Earth as Rotating Sphere

Thunderstorms and Tornadoes
Last Lecture:
We looked at severe weather events in the lower
latitudes
Principal weather event is the formation and movement
of Tropical Cyclones
Today:
Today we will look at severe weather in the midlatitudes
Most severe weather is related to thunderstorms
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Significant convection and precipitation
Very strong winds
Produces thunder and lightning
Can also initiate tornados - most intense wind events on planet
Thunderstorms and Tornadoes
Thunderstorms
Cells of local, intense convection resulting in the formation
of cumulonimbus clouds, heavy rainfall, lightning and
occasionally hail and tornados
Thunderstorms and Tornadoes
Air Mass Thunderstorms
Isolated storms generated by daytime heating of land
surface
Convection Cell
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Severe Thunderstorms
Thunderstorms with high winds, hail and possibly tornados
Thunderstorms and Tornadoes
Mesoscale Convective System
Long-lived, intense cluster of convection cells
Mesoscale Convective Complexes
Large circular complex of thunderstorms active during the night
Thunderstorms and Tornadoes
Squall line
Line of severe thunderstorms and very strong winds
Thunderstorms and Tornadoes
Dry line
Boundary between hot, dry air and warm, moist air, which tends
to form squall line
Thunderstorms and Tornadoes
Lightning
electrical discharge producing light from cloud to cloud or cloud
to ground
Thunder
sound of rapid expansion & cooling of superheated air around a
lightning bolt
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Charge Separation
Difference in charge between cloud top and bottom
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Lightning stroke
Complex series of processes which produce electrical discharge
between cloud and ground
Leader
Channel of ionized air along which lightning stroke propagates
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Tornado
Small, intense cyclonic storm characterized by a funnel descending from
mesocyclone
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Tornado Dynamics
Wind Shear
Convection
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Tornado Dynamics con’t.
Mesocyclone
Tornado
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Tornado Structure
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Weather Conditions during Formation
Cold front
provides
Wind Shear
Squall Line
provides
Convection
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“Tornado Alley”
Region of the United States with high frequency of tornado
occurrence
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Fujita Scale
Measure of strength of tornado based upon severity of damage left
behind
Thunderstorms and Tornadoes
Detection of Tornado Vortex Signature using Radar
Hook Echo