Stormy weather in the Atlantic Hurricanes: As Bonnie moves north, here's a primer on the dangerous and unpredictable tropical storms of late summer and fall.

Sun Journal

August 25, 1998|By Scott Shane

Even as it meandered northwest from the Bahamas yesterday and moved to within a day or two of the East Coast, Hurricane Bonnie already had survived tough competition in the scientific taxonomy of storms.

Of the approximately 100 tropical disturbances that develop each year over the Atlantic Ocean, about 25 develop into tropical depressions and 10 of those go on to qualify as tropical storms.

Of the 10 tropical storms, six become hurricanes by developing sustained winds above 73 miles per hour, the standard definition according to the Beaufort scale, devised by a 19th-century British Naval officer, Sir Francis Beaufort.

Of the six hurricanes, two strike the coast of the United States in an average year.

With sustained winds of 115 miles per hour and gusts to 140, Bonnie qualifies as a Category 3 hurricane on meteorologists' five-point rating scale. Category 5 storms are rare, and Category 3 storms can be devastating.

The National Weather Service in Miami said Bonnie moved "slowly and erratically" yesterday, dawdling at just 4 mph -- walking speed -- after racing as fast as 20 mph over the weekend.

Forecasters expected it to resume moving northwest by last night, with the most likely landfall coming on the coasts of the Carolinas. But they said the hurricane still could move out to sea and miss land altogether. They described Bonnie as an unusually large storm, with hurricane-force winds extending as far as 85 miles from its center.

The sprawling hurricane gave plenty of notice of its advance. Surfers jammed Florida beaches to take advantage of waves as much as four times higher than average for this time of year.

But rip currents spawned by the storm were blamed for two deaths Sunday. In Rehoboth Beach, Del., a swimmer from Silver Spring drowned after being pulled out to sea by a powerful current. At Surfside Beach, S.C., a man was knocked over by a wave and pulled beneath the surface by the undertow. Lifeguards reported that they had rescued 100 swimmers Sunday at Atlantic City, N.J., alone.

The National Hurricane Center near Miami tracks storms using weather satellites positioned 22,000 miles above the equator. The satellites transmit photographs every 30 minutes. Land-based radar can track storms as far as 100 to 200 miles off the coast. The most precise information comes from reconnaissance aircraft that fly near and even through the storms, recording detailed data on size, wind speed, pressure, direction and velocity.

The National Hurricane Center produces an advance list of names for tropical storms and hurricanes, which are in alphabetical order and now alternate between male and female names.

Hurricane Facts:

* The Atlantic hurricane season begins June 1 and ends Nov. 30, with the threat of major storms reaching a peak in early September.

* The strongest hurricane ever recorded was the Florida Keys storm of 1935, a Category 5 hurricane that killed 500 people.

* The deadliest hurricane in U.S. history was a Category 4 storm that hit Galveston Island, Texas, in 1900, taking 6,000 lives with a 16-foot storm surge.

* The costliest hurricane in American history was Andrew, a small but intense storm that hit Florida in 1992 and caused more than $15 billion in damage.

* Even more dangerous than the high winds of a hurricane is the storm surge, a dome of ocean water that can reach a height of 20 feet and extend 50 to 100 miles across.

* Hurricane winds in the Northern Hemisphere circulate in a counterclockwise direction around the eye; in the the Southern Hemisphere the winds circulate clockwise.

Pub Date: 8/25/98

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.