Naturalist's Almanac

The Atlantic hurricane season begins on June 1. It builds toward a peak sometime between mid-August and late October — with the historical date of greatest hurricane activity on September 9 — and ends November 30. Hurricanes begin as tropical storms, but they don't attract much attention until they get named.

A tropical storm gets a name when its winds hit 39 mph, and it becomes a hurricane if the winds hit 74 mph. The alphabetical naming began in 1953 and at first included only women’s names. But in 1979 men’s names were added. Every letter of the alphabet— except Q, U, X, Y, and Z — has six different names because the lists repeat themselves after six years. For a complete list of hurricane names, go to: http://www.nhc.noaa.gov/aboutnames.shtml

The tropical storms that sometimes become named hurricanes originate in Africa. When hot, dry air over the Sahara desert encounters cooler, moister air over the area south of the Sahara — called the Sahel — the collision produces a low-pressure system that drifts out over the ocean.

Storm clouds form and if they cluster, the earth's rotation causes the system to spin counterclockwise. The warm, humid air above the ocean rushes upward into it and starts it spinning faster and faster. When the winds reach 20 mph, the cloud cluster becomes what's known as a tropical depression, which is the precursor of a tropical storm.

While the system is developing into whatever it's going to become, it's also moving westward and northward thanks to the easterly trade winds that predominate in the latitudes between the equator and 30 degrees north. If you look on a globe, you'll see that these storms travel right toward the southeastern United States.

When the first tropical storm gets strong enough to warrant a name, we start hearing about hurricanes in the media. It's always interesting to see which hurricanes are going to do what. A hurricane that's damaging enough might even have its name retired from the six year list.

So far we’ve lost almost fifty names. The letter C has lost the most, with eight hurricanes warranting retirement. Only the letters N, P, S, T, V, and W have survived intact. For a list of all the names that have been retired, go to: http://www.nhc.noaa.gov/retirednames.shtml


These names are no longer available for current or future hurricanes, but they are not lost. They — and the storms they named — have achieved a permanent place in hurricane history.

MORE INFORMATION

USA Today
http://www.usatoday.com/weather/huricane/whhistry.htm

USA Today’s Web site offers quite a bit of its own information on hurricanes plus links to numerous other hurricane sites. Their history section has a long list of links to historical information.

National Oceanic and Atmospheric Administration
http://hurricanes.noaa.gov

The government is, of course, responsible for informing us of and protecting us from hurricanes. They take their responsibility quite seriously, offering several Web sites designed to help people learn about hurricanes. "Hurricanes" is the main site, and it offers numerous links to other government sites. The one I find most interesting is the National Hurricane Center’s Tropical Predication Center http://www.nhc.noaa.gov. I also like Christopher Landsea’s answers to Frequently Asked Questions http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqHED.html and the Federal Emergency Management Agency’s hurricane site for kids http://www.fema.gov/kids/hurr.htm

William Gray
http://typhoon.atmos.colostate.edu

This is William Gray’s Tropical Meteorology Project Web site. Gray and his team forecast the number and severity of hurricanes we will experience each season, and they’re usually pretty close to right. Their forecasts get a lot of press when they first come out. If you want to beat the newspapers, you can go directly to their forecasts at http://typhoon.atmos.colostate.edu/forecasts