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Thunderstorms


Thunderstorms are a frequent part of Florida life. They occur in all seasons of the year in Florida, but they are more numerous during the warm season when the wind off the sea flows inland during the afternoon.  On an annual basis, communities in Florida usually experience thunderstorms 75 to 105 days per year. In fact, Florida leads the United States annually in the number of thunderstorm days.  Out of 100,000 thunderstorms that occur within the United States each year, approximately 1 out of every 10 storms can become severe, causing damage or posing a threat to life. The average thunderstorm contains approximately 275 million gallons of water, which is enough water to fill 416 Olympic-sized swimming pools! 

How Nature Builds a Thunderstorm

Three things need to be present in the atmosphere for a thunderstorm to form.  First, the atmosphere needs to be unstable.  An unstable atmosphere is essentially one where warmer air near the ground will have a tendency to rise higher in the sky, much like a hot air balloon.

Second, there needs to be a source of lift to get the air to rise.  This lifting mechanism can be a cold front, winds from another nearby thunderstorm, or even a cooler breeze off the nearby sea, known as a sea breeze boundary.  The sea breeze is the most common way thunderstorms get their start during the summer months in Florida. The lifting mechanism acts much like a large plow or shovel that forces the air upwards.  Once the lift gets the air to move upwards, then the instability in the atmosphere accelerates the air upwards.

Third, there needs to be enough moisture in the atmosphere to help make clouds as the air rises.  Without moisture, no clouds will form even in the presence of lift and an unstable atmosphere.

Florida experiences more thunderstorms than other states because: (1) Florida is located close to large bodies of water that provide moisture; (2) Florida receives plenty of sunlight, which warms the air near the ground and causes unstable air; and (3) Florida has frequent sea breezes that provide lift for the thunderstorms. Without any of these three things, Florida would not have such numerous thunderstorms.

Stages of Thunderstorm development chart
    Stages of thunderstom development

 

What is a Severe Thunderstorm? 

All thunderstorms are dangerous because they produce lightning, gusty winds and heavy rain which can cause flooding.  Because of the risk of lightning, a thunderstorm does not have to be classified “severe” by the National Weather Service (NWS) to pose a threat to life.  If you can hear thunder, you are at risk of being struck by lightning.  When a thunderstorm threatens your location, move indoors quickly and stay away from windows, plumbing, and electrical devices.

According to the NWS, a thunderstorm is severe when it produces wind in excess of 58 miles per hour, hail one inch in diameter or larger, or a tornado.  Meteorologists at the Storm Prediction Center may issue a “Watch” if conditions are favorable for the development of severe thunderstorms within the next few hours.  In a Watch situation, there is no immediate danger, but you should keep a close eye on the weather. NWS meteorologists issue “Warnings” based on what they see occurring using Doppler radar and other tools.  A Warning means a very strong thunderstorm in the area is capable of causing damage, and is a threat to life and property.  When a Warning is issued, people in the path of the storm should take cover in a well constructed building or storm shelter, preferably in a small central room on the lowest floor with no windows.  Persons in mobile homes should leave them to take shelter in a safer structure. In flooding situations, people should seek shelter on higher ground away from flood prone areas. 

Tracking Thunderstorms

Your National Weather Service maintains seven Weather Forecast Offices that produce forecasts and severe weather warnings for Florida.  These offices are located in Key West, Miami, Tampa, Melbourne, Jacksonville, Tallahassee and Mobile, Alabama.  Once thunderstorms form, meteorologists in the NWS offices track their development and severity using weather data from satellites, storm spotter networks, and Doppler radar.  Modern Doppler radars can not only tell you where the raindrops are falling, they can tell you which way they are being blown by the winds within the thunderstorm cloud.  Using this information, meteorologists can use Doppler radar to detect areas of heavy rain, hail, high winds and even tornadoes.  The NWS operates a network of 10 Doppler radars that cover Florida and NWS meteorologists use their knowledge and expertise to prepare forecasts, statements and warnings based on what they see using weather data.


More information about thunderstorm hazards and what you can do to protect yourself and others can be found at http://www.weather.gov/om/severeweather/ or http://www.floridadisaster.org.

 


  • Monitor NOAA Weather Radio. Listen for "Severe Thunderstorm Watches and Warnings."
  • When skies darken and thunderstorms are in the forecast, look and listen for increasing wind, flashes of lightning, the sound of thunder, or static on your AM radio. These all indicate that a thunderstorm may be heading your way.
  • When severe thunderstorms threaten, move to a sturdy building or car. Do not take shelter in small sheds, under isolated trees, or in convertible automobiles. Avoid windows.
  • Get out of boats and away from water.
  • Telephone lines and metal pipes can conduct electricity. Unplug appliances not necessary for obtaining weather information. Avoid using the telephone or any electrical appliances. Use phones ONLY in an emergency. Do not take a bath or shower.
  • Prior to a severe thunderstorm, move vehicles into garages or carports to help prevent damage, time permitting.
  • Severe thunderstorms produce hail the size of a penny (3/4 inches) or larger.
  • Penny-sized hail or larger can cause significant damage to the exterior surface of your vehicle, break windows and damage roofs of homes and businesses.
  • Penny-sized hail or larger can cause significant bodily injuries such as broken bones and even blindness if wind blown.
  • Severe thunderstorms produce straight wind called downbursts of 58 mph or greater. Downbursts have been measured in excess of 100 mph.
  • Downbursts can cause significant damage even to well-constructed homes, topple or snap large trees, blow down road and commercial signs, and remove roofs from structures.
  • Downbursts can cause damage similar to that of a strong tornado, and cause loss of life or significant bodily injury from wind blown debris and toppled structures.

Updated:

January 24, 2012 15:07