Tornado's
Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.
Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
Nature's Most Violent Storms
Adapted from: A PREPAREDNESS GUIDE Including Safety Information for Schools U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Weather Service September 1992 (NOAA, FEMA, The American Red Cross);
Adapted from: A PREPAREDNESS GUIDE Including Safety Information for Schools U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Weather Service September 1992 (NOAA, FEMA, The American Red Cross);
Weak Tornadoes
69% of all tornadoes
Less than 5% of tornado deaths
Lifetime 1-10+ minutes
Winds less than 110 mph
69% of all tornadoes
Less than 5% of tornado deaths
Lifetime 1-10+ minutes
Winds less than 110 mph
Strong Tornadoes
29% of all tornadoes
Nearly 30% of all tornado deaths
May last 20 minutes or longer
Winds 110-205 mph
29% of all tornadoes
Nearly 30% of all tornado deaths
May last 20 minutes or longer
Winds 110-205 mph
Violent Tornadoes
Only 2% of all tornadoes
70% of all tornado deaths
Lifetime can exceed 1 hour
Lifetime can exceed 1 hour
Only 2% of all tornadoes
70% of all tornado deaths
Lifetime can exceed 1 hour
Lifetime can exceed 1 hour
