Many media outlets have dispatched reporters to the Caribbean and Gulf Coast, hoping to get a first-hand account of Hurricanes Gustav, Hanna and Ike. Maybe next hurricane season, Matt Soniak can join them. (We'll start saving.) For now, his contribution to the national weather conversation is this hurricane FAQ.
Let's start small. What is a hurricane?
Tropical cyclones are storm systems that develop in the tropics, characterized by a low pressure center and thunderstorms that produce strong winds, rain and storm surges. "Tropical cyclone" is a generic term that refers to the storms' geographic origin and cyclonic rotation around a central "eye." Depending on their location and strength, the storms are called by other names. When a tropical cyclone occurs in the Atlantic Ocean and has winds with a sustained speed of at least 74 miles per hour, it's called a hurricane. The same storm occurring in the northwestern Pacific Ocean would be called a typhoon.
What's the difference between a hurricane and a tropical storm?
It's a matter of wind speed. Tropical cyclones, when they're just starting out as general areas of low pressure with the potential to strengthen, are called tropical depressions. They're given a sequential number as they form during the storm season.
Once a storm's winds kick up to 39 mph and sustain that speed for 10 minutes, it becomes a tropical storm, and the National Hurricane Center gives it a name (more on this later).
If the storm keeps growing and wind speeds hit 74 mph, we call it a hurricane.
Once we call it a hurricane, how do we categorize it?
We look to the Saffir-Simpson Hurricane Scale, developed as a classification system for tropical cyclones in the Western Hemisphere in 1971 by structural engineer Herbert Saffir and meteorologist Robert Simpson, who was director of the National Hurricane Center (NHC) at the time.
When Saffir was working for the United Nations to study low-cost housing in hurricane-prone areas, it struck him that there was no scale for describing hurricanes and their damaging effects in a simple way, like the Richter scale is used to describe earthquakes. He created a 1"“5 scale based on wind speed and sent it off to the NHC. Simpson expanded Saffir's work to include the effects of storm surge and flooding and began using it at the Center.
If you want to see a breakdown of the scale, head here.
Is there anything worse than a Category 5?
Not on paper, but there have been hurricanes that have gone beyond the upper bounds of the scale. Hurricane Wilma, which hit the U.S. in 2005, was the most intense hurricane ever recorded in the Atlantic, with winds peaking at 175 mph.
Hypothetically, hurricanes could get even worse. The storms use warm water to fuel themselves. As ocean temperatures rise, climatologists predict that potential hurricane intensity will increase. But don't expect the scale to change. Both Saffir and Simpson have said that there's no need to add more categories because once the winds go beyond 156 mph, the damage looks the same: really bad.
How do hurricanes get their Names?
Since Europeans first came to the Americas and the Caribbean, hurricanes were named using a variety of systems. First they were named after Catholic saints. Later on, the latitude-longitude positions of a storm's formation was used as a name. This was a little too cumbersome to use in conversation.
Military meteorologists started giving female names to storms during World War II, and in 1950 the World Meteorological Organization (WMO) adopted the method. The WMO devised a system of rotating, alphabetical names. (Names can be retired at WMO meetings by request from a nation that has been hit by the storm. The name is then not used for 10 years, which makes historic references and insurance claims easier.)
In 1979, the system was given a dose of political correctness: male names were added to the list, as were French and Spanish names, reflecting the languages of the nations affected by hurricanes.
Today, the WMO uses six lists of 21 names (Q, U, X, Y and Z names are not used) that it cycles through every six years, with the gender of the season's first storm alternating year to year, and genders alternating through the rest of the hurricane season. If there are more than 21 named storms in a year, as there were in 2005, the rest of the storms are named for letters in the Greek alphabet.
Occasionally, a storm suffers something of an identity crisis and has its name changed. This happens when a storm crosses from one ocean to another, or if it dies down and then redevelops.
Will my name be a hurricane this year?
If your name is Nana, then yes. The names being used for the 2008 season are Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gustav, Hanna, Ike, Josephine, Kyle, Laura, Marco, Nana, Omar, Paloma, Rene, Sally, Teddy, Vicky and Wilfred.
See also... Why can't you pump your own gas in Oregon and New Jersey? * Why do we sing the national anthem at sporting events? * Why do we yawn?