Thunderstorms

What causes Thunderstorms Occur inside warm, moist air masses and at fronts. Warm/humid air rises rapidly, cools, condenses and forms CUMULONIMBUS clouds.

Two Types of T-Storms Air Mass T-Storms: (Sporadic) Caused by convection currents of air. Mountain T-Storm – Orographic Lifting Sea-Breeze T-Storm – Afternoon T-Storm at the beach. Most Common T-Storm Frontal T-Storm: (Wall of Storms) Caused by Frontal Lifting: Cold and Occluded Fronts

Stages of a Thunderstorm

Stages of Thunderstorm Development con’t Causes: Think: L.I.M. Lift Instability Moisture Video

Lightning Rapid Uplift of air builds electrical charges. Some parts of the cloud contain negative charges and some contain positive When current flows from (-) to (+) lightning flashes Video: Anatomy of a Lightning Strike

Lightning Pathways Lightning can travel from: Cloud to Cloud Cloud to Ground Ground to Cloud

Lightning & Thunder Results from the rapid heating of air around lightning. Heat causes rapid expansion of the air Molecules move faster than the speed of sound creating a “sonic boom” Video

Determining the Distance of a Thunderstorm For every five seconds between the lightning and thunder, the cell is one mile away.

Tornadoes

How a tornado starts: Winds are stronger aloft than at the surface (called speed wind shear), producing a rolling motion about a horizontal axis. Strong thunderstorm updrafts tilt the horizontally rotating air to a nearly vertical alignment. The mesocyclone, a vertical cylinder of rotating air, is established.

Tornado Formation

Facts about An average of 800 tornadoes are reported in the United States every year Fastest tornado wind reported was 286 miles an hour in Wechita Falls Texas The state that has the highest number of tornadoes a year is Texas with an average of 125

Myths about tornadoes Highway overpasses are a safe place to shelter if driving on the road Tornadoes never strike big cities The part of the basement towards the approaching tornado is the safest

Fujita Scale The Enhanced Fujita scale classifies tornadoes according to the damage they cause. Scale Ranges from: F-0 to F-5 Created by Ted Fujita

FUJITA SCALE OF TORNADO INTENSITY Rating Wind Speed Damage F-1 73 - 112 mph Rips shingles off roofs; flips mobile homes.

FUJITA SCALE OF TORNADO INTENSITY Rating Wind Speed Damage F-2 113 - 157 mph Upturns and flips boxcars.

FUJITA SCALE OF TORNADO INTENSITY Rating Wind Speed Damage F-3 158 - 206 mph Exterior walls and roofs blown off homes. Metal buildings collapsed or severely damaged. Forests and farmland destroyed.

FUJITA SCALE OF TORNADO INTENSITY Rating Wind Speed Damage F-4 207 - 260 mph Few walls left standing. Large concrete blocks launched far distances.

FUJITA SCALE OF TORNADO INTENSITY Rating Wind Speed Damage F-5 261 - 318 mph Homes flattened with all debris removed. Schools, motels, and other larger structures damaged considerably with exterior walls and roofs gone. Top floors demolished.

F – 5 Tornado Destruction

Tornado Alley The area of the United States in which tornadoes are most frequent. Tornado Alley includes the Mississippi, the Ohio, and lower Missouri River Valleys. Although no state is entirely free of tornadoes, they are most frequent in the Plains area between the Rocky Mountains and Appalachians.