By GREG AINSWORTHThis year's hurricane season in the waters adjacent to the Southeastern United States is drawing more attention than usual, thanks to the oil spill in the Gulf. The National Hurricane Center expects a busier than average year, so it's time to energize our hurricane IQ.
Whether you call them hurricanes, typhoons or cyclones, they are the scourge of tropical locales worldwide. Ocean water temperatures of at least 80 degrees seem to be one of the key ingredients in their formation. Think hot and muggy -- and lots of evaporation. If other conditions are favorable in the atmosphere, winds near the surface may begin to converge, and a low-pressure system may form.
In the Northern Hemisphere, those cyclonic winds spiral in a counter-clockwise direction. All of that water vapor in the atmosphere rises and condenses inside thunderstorm complexes, releasing a great amount of energy in the process. Bands of thunderstorms stretching from the system's outer margins to the center of circulation help feed the massive heat engine with warm, moisture-laden air.
As the system matures, the characteristic cloud-free and relatively calm eye may form at the center of circulation. But surrounding the eye is the eyewall, where the most intense convection and highest wind speeds occur.
Hurricanes pose a major threat to life and property because of their ability to wreak havoc in so many different ways. Perhaps the first thing that comes to mind is wind damage -- not surprising since a storm isn't called a hurricane until it has sustained winds of at least 74 mph. In August 1969, Hurricane Camille made landfall along the Mississippi coast with sustained winds estimated at 200 mph.
An important, but often overlooked hurricane impact is the storm surge. This refers to the ocean water pushed onshore into low-lying areas by hurricane-force winds. Depending on the status of the local tides during landfall, storm surges of 15 to 20 feet are not out of the question. If you happen to live in a near-shore area at say, 10 feet above sea level, the surge can be bad news indeed. Hurricane Opal caused a 24-foot storm surge near Pensacola, Fla., in September 1995.
Even days after landfall, hurricanes, or their remnants, are still capable of producing tornadoes and flooding rains. After slamming into the coast of south Texas in September 1967, Hurricane Beulah spawned more than 100 tornadoes. Tropical Storm Claudette, whose winds didn't reach hurricane strength, nevertheless dropped 45 inches of rain on Alvin, Texas, in 1979.
For further information about these storms, check out the website for NOAA's National Hurricane Center.
Greg Ainsworth keeps an eye on local weather and climate issues. Contact him at ainsworth@theglobal.net.
