The City of Titusville, Florida / Emergency Management / Natural Disasters / Severe ThunderstormSevere Thunderstorm
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.
Severe Thunderstorm Summary
- Moisture needed to form clouds and rain
- Unstable Air relatively warm air that can rise rapidly
- Lift Mechanism fronts and sea breezes to lift the air upward
- Where do these ingredients come from?
- Moisture Atlantic Ocean, Gulf of Mexico, Caribbean Sea
- Unstable Air Abundant sunshine heating the air near the ground
- Lift Mechanism Afternoon east and west coast sea breezes including bay breeze. Also, late fall, winter or early spring fronts
Thunderstorm Safety Actions
- Monitor NOAA Weather Radio. Listen for “Severe Thunderstorm Watches and Warnings.”
- In vehicles, avoid driving into severe thunderstorms. Consider pulling over or delaying travel.
- When severe thunderstorms threaten, go to a small interior room on the lowest floor of your home, school or business. Avoid windows.
- Prior to a severe thunderstorm, move vehicles into garages or carports to help prevent damage, time permitting.
- Severe thunderstorms produce hail the size of dime (3/4 inches) or larger.
- Dime-sized hail or larger can cause significant damage to the exterior surface of your vehicle, break windows and damage roofs of homes and businesses.
- Dime-sized hail or larger can cause significant bodily injuries such as broken bones and even blindness if wind blown.
- Softball-sized hail was reported in Lake Wales, Florida on March 30, 1996. Hailstones the size of softballs can fall at speeds faster than 100 mph.
- Haildrifts, up to four feet deep of dime- to nickel-sized hail, occurred in low-lying areas near Zephyrhills, Florida on January 29, 1997.
- 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.