High-pressure 'Glob' Culprit In Heat Wave

June 9, 1985|By Charlie Jean of The Sentinel Staff

You might say it was as if Mother Nature had placed a great magnifying glass over the Southeast last week.

It was going to get very hot and stay that way until somebody took away the glass -- and only nature was strong enough to do so.

The heat wave began last weekend when a huge mountain of heavy and dry air -- a high-pressure system -- spread over the entire Southeast, the western Atlantic, the Northern Bahamas and half of the Gulf of Mexico.

It centered itself about 150 miles west of Tampa and parked, its winds spinning slowly clockwise. It wasn't going to move until some other strong weather system came along to nudge it back out into the Atlantic.

It was the reverse of a low-pressure system -- the counterclockwise- flowing seeds of hurricanes.

In nature's unending quest for equilibrium, low pressure over Florida attracts moist breezes from the coasts and, as they are warmed by land, sends them spiraling skyward -- the making of summer thunderstorms.

But high pressure sits there, brooding, serving as a big dome and trapping what's inside -- the heat, the smoke, the dust particles. It's more like a big glob of mud that tends to settle than like warm air sucked up a chimney into winter skies.

''It more or less stagnates and gets warmer,'' said forecaster Burt Sylvern of the National Weather Service in Miami.

Making it worse, light cloud cover sometimes formed, making it more difficult to lose heat by radiation at night.

The air couldn't rise to form storms because it was covered by air just as hot or hotter. Cooler lower air and warmer higher air formed an inversion, trapping the heat and accumulating pollutants and smoke close to earth.

Hence, haze began to develop over parts of the state early in the week.

Moreover, the system's circulation pattern was bringing in dry air from the Plains, further diminishing the chance of storms.

Coming from the west, the circulation cut off the cooling breezes that normally flow westward from the Atlantic.

Though the Plains air was relatively dry, humidities gradually rose, making it feel hotter than the thermometer said it was.

Government scientists worked out a formula called the heat index, which says, for example, that an air temperature of 100 degrees and a relative humidity of 50 percent would have the same effect on the human body as a temperature of 120 degrees.

Such high-pressure systems were the backbone of the three-month summer heat wave of 1980, which weather experts say claimed at least 1,250 lives.

''But these are direct casualties,'' one forecaster said. ''No one knows how many other deaths were advanced by heat waves.''

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