1. Thermodynamics of Tornadoes and Hurricanes Daniel Crnkovich 24 November 2009

2. Tornadoes and Hurricanes Tornadoes Tornadoes Form over land Form over land If a tornado forms over water it becomes a cyclone If a tornado forms over water it becomes a cyclone Damage due to wind Damage due to wind Scaled from F0 – F5 (Fujita Scale) Scaled from F0 – F5 (Fujita Scale) Hurricanes Hurricanes Form over water Form over water Starts a tropical depression or storm Starts a tropical depression or storm Damage due to water Damage due to water Scaled from 1 – 5 (Simpson Scale) Scaled from 1 – 5 (Simpson Scale) Both are hard to predict and cause extensive damage Both are hard to predict and cause extensive damage

3. Causes of Hurricanes and Tornadoes Coriolis Force Coriolis Force Inertial force of the Earth Inertial force of the Earth Angular Momentum Angular Momentum Air factors Air factors Temperature difference Temperature difference Pressure difference Pressure difference Water factors Water factors Temperature difference Temperature difference Colliding pressure fronts Colliding pressure fronts

4. Thermodynamics of a Hurricane Hurricanes modeled by the Carnot Cycle Hurricanes modeled by the Carnot Cycle Isothermal expansion (3-4) Isothermal expansion (3-4) Formation of eye Formation of eye Increase in entropy Increase in entropy Driving force of storm Driving force of storm Adiabatic expansion (3-4) Adiabatic expansion (3-4) Air rises to top of eye wall Air rises to top of eye wall Lower P and T Lower P and T Isothermal compression (4-1) Isothermal compression (4-1) Cloudy air travels to edge of hurricane (about 200 miles) Cloudy air travels to edge of hurricane (about 200 miles) Decrease in entropy Decrease in entropy Adiabatic compression (1-2) Adiabatic compression (1-2) Return to original state Return to original state

5. Thermodynamics of a Tornado Warm and moist air mass Warm and moist air mass Lead eastward-moving cold fronts Lead eastward-moving cold fronts Common in the spring Common in the spring No thermodynamic model has been found for tornadoes No thermodynamic model has been found for tornadoes Often influenced by particle charges differences Often influenced by particle charges differences Physics based Physics based

6. Predicting Hurricanes and Tornadoes Hurricanes take time to form Hurricanes take time to form Succession of tropical depression, storm, strengthening Succession of tropical depression, storm, strengthening Weaken due to land Weaken due to land Once formed, predicting the path can be difficult Once formed, predicting the path can be difficult Tornadoes form quickly Tornadoes form quickly Super-cell thunderstorms Super-cell thunderstorms “Tornado alley” “Tornado alley” Warm and moist air masses followed by cold fronts Warm and moist air masses followed by cold fronts Future technologies may help in predictions Future technologies may help in predictions

7. Questions? Photos courtesy: google.com; NASA; NOAA Sources: NASA; NOAA; auf.asn.au; charles-chandler.org/Geophysics/Tornadoes Full.php