On the Trail: Stormy summers

Tampa is the lightning capital of Florida and Florida is the lightning capital of the world. "Tampa" is the Seminole word for lightning and, after a trip along the central coast of Florida in the summertime, anyone could see why. Thunderstorms around Tampa Bay are routinely the strongest on radar with thousands of lightning strikes every 24 hours.

Southwest Florida may not have the rating as thunderstorm capital of Florida, but every local here has a story of being caught in a thunderstorm.

We know that most mornings are clear, but as the afternoon progresses that old familiar thunder will start rumbling in the distance.

Afternoon thunderstorms are not unique to Florida, but the hot humid weather certainly does add fuel to the fire. What really makes our thunderstorms fast and furious is that we live on a narrow peninsula.

In Florida, the land cools rapidly after sunset, but water temperatures remain nearly constant. Even in summer, overnight inland temperatures will drop into the 70s, but the Gulf and Atlantic waters hold steady in the mid-80s — even higher in the Gulf.

With the warmer air rising over the water and the cooler air settling over the colder ground, we have a temperature inversion that creates an offshore breeze. The cooler air from the land rushes out to fill the gap from the warm air rising over the water.

On a normal summer morning, easterly breezes prevail until the sun starts climbing and heating the land. In summer, humidity levels are higher and with every rising degree in land temperature, moisture begins streaming aloft. As the land heats and the warm air rises, stronger columns of vertical development occur. By late morning, the land temperature will become as warm as the Gulf.

This is when golfers out on the course, wipe the perspiration off their brow and say, "What happened to the breeze?"

The offshore breeze stops when there is no longer a temperature inversion — when the land heats to the same temperature as the water the wind stops — but not for long.

As the land becomes warmer than the water, a new temperature inversion develops — this time with the warmer air rising over the land. This is the moment when beachgoers rethink their plans for retreating into the air-conditioning and decide to stay under their umbrella and enjoy the sea breeze.

As the afternoon progresses, the sea breeze becomes stronger. This is because the Gulf sea breezes and the Atlantic sea breezes begin to converge. With the wind rushing inland from both our coasts, the warm moist air has only one place to go — straight up.

As the land heats, hot columns of vertical air rise like invisible chimneys over the center of the state. As the converging sea breezes supply the thunderstorm fuel, the warm, moist air rushes higher and faster. At ground level, we may have a thermometer reading of 90 degrees, but with every thousand feet higher, the temperature drops 2 degrees.

Weather forecasting manuals describe cumulonimbus clouds as the vertical development cloud that can reach 45,000 feet. I have met airline pilots who have said these thunderstorm clouds can go up to 65,000 feet. Even with a ground temperature of 90 degrees, at 45,000 feet the thermometer will show a frosty zero.

As the warm, moist air travels higher and faster, it rapidly cools and becomes heavier. When the outer edge of the cloud becomes saturated with condensing moisture, rain begins.

Friction caused by rapidly moving molecules creates a static charge and when electrical levels in the clouds peak, lightning is the discharge of an electrical arc searching for ground.

High, puffy, cotton-topped clouds are friendly and show vertical development that stopped or drifted apart, but when we see the tight, swelling clouds that resemble a growing head of cauliflower and are dark at the base — watch out!

For many years, I have watched the summertime weather. As a charter captain, like all my colleagues, I have learned to follow some basic rules:

• (1) If the clouds are building and you are thinking about going in — you should already be heading in.

• (2) Never try to run offshore to escape a storm — they are bigger and faster than you are.

• (3) If you are a sailor considering taking your sails down because of an approaching squall line — you should already have them down. Don't worry, if you don't know when to take them down, God will take them down for you. This also pertains to umbrellas at the beach or poolside.

• (4) There is no such thing as an atheist in a boat during a storm!