It's Raining Fish and Spiders (10 page)

When a tropical depression's winds exceed 38 mph, it has become a tropical storm. The clouds have taken on a more well-defined, circular shape. Thunderstorm bands are flowing out from the center. Beneath this storm, the winds are so strong and the seas so rough, that ships must now avoid the area. A tropical storm's winds will range from 39 to 74 mph.

The storm is now drawing more heat and water vapor from the sea. It has a column of warm air near its center. As this column becomes warmer, air pressure at the ocean's surface falls. The falling pressure draws more air into the storm and the storm grows stronger.

This is the point in the storm's life where it is given a name.

Hurricane

In these pictures of Hurricanes Felix and Dean, you can see a well-defined, concentric pattern of clouds and a well-formed eye. A storm achieves hurricane status when its winds are in excess of 74 mph. In the eyewall, warm air spirals upward, creating the hurricane's strongest winds. The speed of the winds in the eyewall is related to the diameter of the eye. A hurricane's winds blow faster if the eyewall is small; if the eye widens, the winds decrease.

Hurricane Dean

Hurricane Felix

The hurricane is now drawing large amounts of heat and moisture from the sea. Heavy rains are falling from the spiral or feeder bands—as much as 2 inches per hour—and the seas are churning dangerously as the storm surge builds!

How Do Hurricanes Get Their Names?

There's a great novel by George R. Stewart,
Storm
, which I assign to all my student interns.
Storm
is very popular among meteorologists. Written in 1941, and still relevant, it's about a forecaster who used women's names for naming storms.

The idea must have made quite an impact on weathermen; during World War II, military forecasters began to formally attach women's names to storms. Naming helps forecasters avoid confusion and keep track of the storms; it also helps researchers keep things straight. Most times during a hurricane season, there can be two or three storms at a time on the Atlantic and as many as two or three in the Pacific. That's a lot of storms, and giving them names makes it easier to track and keep up with them as well as to go back and research them later.

Each year, the World Meteorological Organization (WMO), an agency of the United Nations, issues four alphabetical lists of names for tropical storms. There's one list for the northern Atlantic Ocean and the Caribbean Sea, and one list for each of the regions of the Pacific Ocean: eastern, central, and northwestern. The lists include both men's and women's names that are popular in countries that might be affected by the storms in each area. As the equality movement prevailed across the United States, the practice of using men's and women's names was started in 1978 in the eastern Pacific and the following year in the Atlantic and Gulf of Mexico.

Except in the northwestern and central Pacific, the first storm of the year gets a name beginning with A—such as Tropical Storm Ana. If the storm intensifies into a hurricane, it becomes Hurricane Ana. The second storm gets a name beginning with B, and so on through the alphabet. The lists do not use all the letters of the alphabet since there are few names beginning with such letters as Q or U. Also, no Atlantic or Caribbean storms receive names beginning with Q, U, X, Y, or Z.

In the northwestern and central Pacific, the lists include names of animals and things as well as people. For instance, a typhoon was named after a cricket or a cicada in a certain country's language.

You Have Been Retired from the Game!

Hurricanes that have a severe impact on people's lives and are devastating to property and the economy become part of weather history, and are remembered for generations. When a storm of this magnitude occurs, any country affected by the storm can request that the storm's name be retired by the World Meteorological Organization. Here is a list of major Atlantic and Caribbean hurricanes whose names will no longer be used.

Hurricane Dennis
NASA