It's lightning season - so be careful
Published: Thursday, July 1, 2010 at 6:01 a.m.
Last Modified: Wednesday, June 30, 2010 at 2:52 p.m.
Several times a week during summer, thunderstorms build, there's a flash in the sky, and the counting begins: "One 1,000, two 1,000, three..."
Then the thunder claps. The rule of thumb used to be that the number reached in the count equals the number of miles away that the bolt struck.
If you think that theory is true, think again. Every second actually equals about 1,056 feet, or one-fifth of a mile. Thus, five seconds equals one mile, not five.
If you are outdoors, by the time the mileage can be calculated it is too late. Light travels faster than sound, so when light flashes, the bolt has struck before the thunder sounds.
For Floridians, this isn't some academic exercise. The state is the lightning capital of North America, and an area from Tampa east through Orlando's theme parks to Cocoa Beach, and north to the southern fringes of Marion County, is considered "Lightning Alley" - the most dangerous zone in the most dangerous state.
In this hot zone, there are at least 150 lightning flashes per square mile annually - 30 of which strike the ground.
Though most of Marion County, and all of Alachua County, are north of that hot zone, there are still more than 20 strikes in Alachua County and 25 strikes in most of Marion per every square mile annually.
Ed McPadden, the Marion County School District's extra-curricular activities director, offers a simple safety rule.
"If you see it [lightning], hear it [thunder], clear it [the field]," he said.
And really, area officials say, that is the best rule for recreators: the golfer, the swimmer, the gardener, the landscaper - anyone outdoors.
Across Marion County's 1,600-plus square miles, each year there are roughly 200,000 flashes and about 40,000 strikes. Across Alachua County's 875 square miles, there are roughly 87,500 flashes and 17,500 strikes annually.
Though these counties are just outside Lightning Alley, both are still located in the most dangerous lightning area in the United States. This area of the country has a lightning rate at least four times the national average.
When lightning is first observed, it is time to go to a building or a vehicle.
David Donnelly, Alachua County's emergency management director, urges residents to use portable weather radios when outdoors, whether fishing, golfing or relaxing in the back yard.
"I believe that's the most important tool," he said, adding that knowing when severe thunderstorms are approaching is crucial.
That's because one lightning bolt has 1 million volts of electricity and generates about 50,000 degrees of heat, more than four times hotter than the sun.
The Lightning Safety Institute estimates that there are about 125 million flashes of lighting across the United States each year, about 25 million of which hit the ground.
Lightning causes at least $2 billion in damages across the country, though some estimates have topped $5 billion.
Florida is the lightning capital of North America because it is surrounded by water on three sides. Within its 1,200 miles of coastline are 58,250 square miles of land, nearly 10 percent of which is land-locked water.
During summer afternoons, the land warms up faster than the water to produce sea and lake breezes. These breezes force the moist warm air up from the surface until it meets the colder, drier atmosphere.
In this area, Gulf of Mexico and Atlantic Ocean breezes collide along the Interstate 75 corridor to form severe thunderstorms.
Lightning forms when rising and sinking air within a thunderstorm separates into positive and negative charges, created after clouds fill up with water and the drops bump together when it falls.
Charges also form on land and create an electrical imbalance. Lightning is formed in hopes of settling the imbalance.
One lightning bolt, which can be as long as 10 miles, has more than 1 million volts, enough to burn a 100-watt light bulb for three months.
Lightning is a series of electrical impulses and can travel 60,000 miles a second, one-third the speed of light. A bolt starts and finishes in 1/10,000th of a second. The lightning bolt can go cloud to cloud, ground to cloud or cloud to ground. About 80 percent of lightning never hits the ground.
Southeastern states receive on average about six lightning strikes per square mile annually, while states in the Northeast and Midwest average about three strikes per square mile. West Coast states receive less than one lightning strike per square mile per year.
Since 1959, 3,919 people have been killed in the United States by lightning; 460 have been killed in Florida, which leads all states.
But Florida is not even close to the lightning capital of the world. That distinction goes to the Democratic Republic of the Congo in Central Africa, which features 409 lightning flashes (82 strikes) per square mile annually.
That's based on research conducted by Steve Goodman of NASA's Global Hydrology and Climate Center in Huntsville, Ala. Using satellite imagery, he created a world lightning flash map.
In South America, Colombia features 285 flashes (57 strikes), Northern Pakistan sees 225 flashes (45 strikes) and Florida features 153 flashes (31 strikes) per square mile annually.
Most every government agency relies on the 30-30 rule to protect employees working outdoors.
That rule: If the time between a flash and the thunder is less than 30 seconds, or within six miles, move to a safe place, preferably indoors or a vehicle.
Only return outside when 30 minutes has passed after the last flash of lightning.
The state high school association pushes the 30-30 rule as a guide when it comes to lightning. Sonny Hester, the Florida High School Athletic Association's associate executive director, said they do not require, or even suggest, that hand-held devices should be used.
The organization decided to stand clear of the devices, mainly because they are not 100 percent accurate. Hester said the 30-30 rule is the association's recommendation.
Alachua County's School District follows the recommendation set by that association.
McPadden said the Marion School District considers the hand-held devices an extra tool in protecting students on the field.
Marion sheriff's Capt. Chip Wildy, the county's emergency management director, who also is a high school football referee, follows one basic rule.
"If we see a flash, clear the field," said Wildy, adding that it doesn't matter if it is more than six miles away or not.
Wildy said he is always amazed at the reaction when athletes are cleared off the field due to lightning.
Many of the spectators remain outside on the sidelines, or in the stands, and should also be heading indoors or to their vehicle.
"There's no need to take a chance," he said.
Joe Callahan is an Ocala Star Banner staff writer.
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