Thunderstorms are part of life in Florida. They are nature’s way of providing badly needed rainfall, dispersing excessive atmospheric heat buildup and cleansing the air of harmful pollutants. No other state in our country has more of them. Why? Simply put, all the right ingredients to produce thunderstorms are available in Florida throughout most of our long warm season.
On average, the interior sections of central Florida receive the most thunderstorms with nearly 100 plus days per year. However, thunderstorms are also frequent along coastal areas which average 80 to 90 days per year. Although Florida thunderstorms are generally less than 15 miles in diameter, they can grow vertically to great heights in excess of ten miles high into the atmosphere. This stacking effect of concentrated moisture can explain why a Florida thunderstorm directly overhead could produce four or more inches of rain in less than an hour while a location a few miles away may see only a trace.
All thunderstorms are dangerous. Every Floridian should understand, respect and know how to protect themselves from the effects of thunderstorms. Lightning, tornadoes, downbursts, hail and flooding rainfall are all dangerous by-products of thunderstorms that could be lethal to the unknowing and unprotected.
Severe Thunderstorms vs. Ordinary Thunderstorms?
Although every thunderstorm in Florida has the potential to cause death, injury or damage, about ten percent produce dangerous winds or hail that will likely exceed thresholds known to cause significant damage to well-built structures or cause bodily harm. These are known as severe thunderstorms. Severe thunderstorms produce hail the size of a dime or larger and/or winds of 58 miles per hour or greater. The National Weather Service issues Severe Thunderstorm Warnings for a particular county, or portions of it, when the above conditions are expected to be met or are ongoing.
Severe Thunderstorm Hazards
Strong rising currents of air called updrafts carry water droplets high into the upper reaches of thunderstorms where they freeze. These frozen water droplets fall back toward the earth in descending currents of air called downdrafts. In their descent, these frozen droplets bump into and coalesce with unfrozen water droplets and are then carried back up high within the storm where they refreeze into larger frozen drops. This cycle may repeat itself several times until the frozen water droplets become so large and heavy that the updraft can no longer support their weight. Eventually, the frozen water droplets fall back to earth as hailstones.
Storms that produce hailstones the size of a dime or larger can produce dents in the tops of vehicles, damage roofs, break windows and cause significant injury or even death and thus are considered severe. Large hailstones can fall at speeds faster than 100 miles per hour. These severe hail storms cause nearly one billion dollars in damage to property and crops annually.
In fact, a single severe thunderstorm produced nearly $15 million worth of property damage in Lake Wales, Florida on March 30, 1996 from hailstones the size of softballs.
Thunderstorms produce two types of wind. The tornado, which is spawned from a severe thunderstorm, is a rotational wind. The other, more predominant wind from a thunderstorm is called a downburst, which is a straight wind. In Florida, the occurrence of downburst (straight) winds outnumber tornado (rotational) winds from a severe thunderstorm by nearly a ten-to-one ratio.
Every thunderstorm produces a downburst. The old adage, what goes up, must come down, holds true for the rising air in every thunderstorm. The typical 25 miles per hour gusty breeze, accompanied by a temperature drop of as much as 20 degrees in a few minutes, is the downburst we feel from a distant thunderstorm. However, when downburst winds are 58 mph or greater, potential damage to well constructed homes increases significantly.
Downburst winds of 58 mph or greater are considered severe. Downburst wind can produce widespread damage similar to that of a tornado. In fact, some downburst winds have been measured in excess of 120 miles per hour, or equivalent to an F2 tornado, on the Fujita Scale.
Thunderstorm Safety Actions