A thunderstorm affects a relatively small area when compared to a hurricane or a winter storm. The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Despite their small size, ALL thunderstorms are dangerous! Of the estimated 100,000 thunderstorms that occur each year in the United States, about 10 percent are classified as severe.
What Are Thunderstorms?
What Causes Them?
Every Thunderstorm Needs:
■ Moisture—to form clouds and rain
■ Unstable air—warm air that can rise rapidly
■ Lift—caused by cold or warm fronts, sea
Why Worry About Thunderstorms? Lightning...
■ Causes an average of 55-60 fatalities and 400 injuries each year
■ Occurs with all thunderstorms
■ Costs more than $1 billion in insured losses each year Tornadoes...
■ Cause an average of 60-65 fatalities and 1,500 injuries each year
■ Can produce wind speeds in excess of 200 mph
■ Can be 1 mile wide and stay on the ground over 50 miles Straight-line Winds...
■ Can exceed 125 mph
■ Can cause destruction equal to a tornado
■ Are extremely dangerous to aviation Flash Floods and Floods...
■ Are the #1 cause of deaths associated with thunderstorms, more than 90 fatalities each year Hail...
■ Can be larger than a softball (5 inches in diameter)
■ Causes more $1 billion in crop and property damage each year 1
All information supplied by:
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Weather Service
