Tornadoes

Tornado Formation• Severe “Super Cell” Thunderstorm (1% spawn

tornadoes)• Often occur along cold fronts and move to NE• Strong updrafts• Wind shear (change in direction or strength of

winds from top to bottom of storm)

Funnel Cloud v. Tornado

Tornado Funnel Cloud

Waterspout- over water - less power- smaller tempgradient

World Tornado Geography

• USA: 90%+ of all tornadoes

USA Tornado Geography

• Every state!• Tornado Alley (TX, OK, KS, NE)

USA Tornado Season

Most common when temperature gradient in central U.S. is greatest.

USA Tornado Occurrence

• About 800-1000 tornadoes spotted each year.

Tornado Classification• Fujita F-scale

– F0 (winds < 120 mph) to F5 (winds 200-300+ mph)– based on rotational wind speed and damage done

• Size: Tornadoes generally < 1/4 mile wide (damage path only 150 ft.)

Deadliest Tornado• Tri-state tornado outbreak of March 18, 1925

• Kills 689 people in Missouri, Illinois & Indiana

Largest Tornado Outbreak

• April 3-4, 1974 Super-Outbreak

• 148 tornadoes overnight across 11 states

Tornado Forecasting• NEXRAD doppler radar (WSR-88D)

– 138 stations across the USA• Intensity of storm noted by amount of reflection off rain,

hail, and ice crystals.• Hook cloud is an indicator.

Orlando, Florida

Tornado Indicators• What to look for….