for National Geographic News
Fueled by the warm late-summer waters of the Gulf of Mexico, Hurricane Rita exploded overnight into the third-most powerful hurricane on record for the Atlantic Basin.
As of 5 a.m. today the hurricane's strongest winds were blowing at 175 miles an hour (280 kilometers an hour) and the barometric pressure at the storm's center had fallen to 26.51 inches, or 897 millibars.
Since the invention of the barometer in the 17th century, a hurricane's lowest barometric pressure reading has become a standardized way for meteorologists to measure a storm's intensity.
As a hurricane gains strength, its barometric pressure reading drops. A normal barometric pressure reading at sea level during calm weather is roughly 30 inches, or 1,000 millibars.
The lowest barometric pressure reading recorded in the Atlantic Basin was Hurricane Gilbert in 1988, with a reading of 26.18 inches, or 888 millibars. Gilbert struck Mexico's Yucatán Peninsula. The second-lowest reading on record was 26.35 inches, or 892 millibars, during the Labor Day hurricane of 1935. That hurricane struck the Florida Keys.
Residents Flee Gulf Coast
More than a million people on the hurricane-battered Gulf Coast are moving inland today to escape Rita's ferocious winds.
"Traffic is horrible now," said Robert Arnold, a resident of the Houston suburb of Sharpstown. "People are gridlocked, pulled over on the side of the road. People are running out of gasoline. It's very difficult to get gasoline."
Hurricane Rita is the fifth powerful hurricane to strike the Gulf Coast since August 2004 and the second Gulf hurricane in less than a month to reach Category Five status on the Saffir-Simpson scale.
Hurricane Katrina reached Category Five status shortly before it weakened and struck southeastern Louisiana on August 29 with winds of more than 140 miles an hour (225 kilometers an hour). Katrina's storm surge caused devastating flooding in New Orleans, and the hurricane inflicted massive damage in Mississippi.
The series of powerful Gulf Coast storms started with Hurricane Charley, which made landfall at Punta Gorda on the west coast of the Florida peninsula in August 2004.
"When hurricanes get into the Gulf, they're going to hit something," said Gary Beeler, a meteorologist at the National Weather Service office in Mobile, Alabama.
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