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 temp
gradient
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….