Severe Thunderstorms

Introduction

All thunderstorms are dangerous despite the fact that they are generally localized in a small geographical region. It is important to note that every thunderstorm produces lightning, which is responsible for more deaths annually than hurricanes or tornadoes. Severe thunderstorms can lead to flash flooding, straight-line winds of 100 to 150 mph, damaging hail and tornadoes. A typical thunderstorm is 15 miles in diameter and lasts for 20-30 minutes. On average, 100,000 thunderstorms occur in the United States each year with 10% (10,000) classified as severe.

The National Weather Service considers a thunderstorm severe if it has wind gusts of over 58 mph, hail that is 3/4 inch in diameter or larger or produces a tornado.

Severe Thunderstorm WATCH  means that severe storms are possible and it is important to keep informed of the weather reports and be ready to find shelter if a warning is issued.

Severe Thunderstorm WARNING indicates that severe weather has been reported by spotters and there is imminent danger to life and property.

General Resources

The National Weather Service (NWS) and the American Red Cross have developed two preparedness guides which discuss severe storms in detail and also provide safety information:  Thunderstorms and Lightning...the underrated killers!  and Nature's Most Violent Storms.

The National Oceanic and Atmospheric Administration (NOAA) has developed a severe weather planning guide for schools.   

Current nationwide severe weather maps and are state specific have been made easily accessible through the efforts of Tom Priddy, EDEN POC at the University of Kentucky.

NOAA Weather Radios (NWR) provide "all hazards" emergency alert messages and the receivers are recommended equipment for all homes and businesses by public safety experts.   The website provides information on purchasing the radios, the emergency alert system (EAS) and Specific Area Message Encoding (SAME). It also has suggestions for radios for people with special needs. 


Lightning Safety

Lightning is a major threat during a thunderstorm because it is very unpredictable and it can strike as far as 10 miles away from the actual rainfall area. An average of 62 people are killed from lightning strikes each year with the majority of deaths occurring to people who did not seek inside shelter during the storm. Many more injuries occur and some may result in long-term, debilitating symptoms such as memory loss, sleep disorders, attention deficits, irritability, depression and muscle spasms.

Do you know the 30/30 rule for lightning safety? First 30: if there are 30 seconds or less between the lightning flash and hearing thunder, then the lightning is close enough to strike you -- go inside immediately.  Second 30: wait 30 minutes after the last lightning flash before leaving your inside shelter area.

Lightning Resources:

NOAA has developed a lightning safety website and promotes Lightning Safety week which is June 22-28, 2008.

Coaches and Sports Officials Guide to Lightning Safety  (NOAA)

Safety Tips for the Mariner (NOAA)

Struck by Lightning - First Aid  (American Red Cross)