Hurricane Dean Slams Mexico Coast

Willie Drye
for National Geographic News

August 21, 2007

Gaining power up until the moment it touched land, Hurricane Dean struck the southern Yucatan Peninsula early Tuesday with winds of 165 miles (265 kilometers) an hour.

Dean came ashore as a Category 5 hurricane, a classification reserved for the most intense storms. The tempest is the first Category 5 storm to come ashore in the past 15 years.

The hurricane's eye made landfall around 4:30 a.m. near Majahual, a seaport about 40 miles (64 kilometers) notheast of the Mexico-Belize border (see map).

By 8 a.m. the storm had weakened to a Category 3 hurricane, meaning that its winds had dropped to less than 131 miles (211 kilometers) an hour.

The hurricane's powerful winds are expected to cause catastrophic damage as it crosses the peninsula.

Forecasters also predict the storm will dump at least 5 to 10 inches (13 to 25 centimeters) of rain, with some places receiving as much as 20 inches (51 centimeters).

The heavy downpour is expected to cause deadly flash floods and mudslides.

Meteorologist Dennis Feltgen at the National Hurricane Center in Miami said Dean was expected to push a storm surge of 12 to 18 feet (3.6 to 5.5 meters) as it came ashore.

Crossing Land

Powerful hurricanes like Dean have very low barometric pressure readings in their eyes. At sea level during calm weather, the normal barometric pressure is about 30 inches (a thousand millibars).

Dean's barometric pressure reading of 26.74 inches (906 millibars) makes it the ninth most powerful hurricane on record in the Atlantic Basin, which includes the Caribbean Sea and the Gulf of Mexico, Feltgen said.

Dean also became the first Category 5 hurricane to make landfall since Hurricane Andrew struck southern Florida in 1992.

By contrast, Hurricane Katrina had been a Category 5 storm as it roared toward the Gulf Coast, but had downgraded to a Category 4 when it made landfall near New Orleans in August 2005.

Forecasters think Dean will weaken as it crosses the Yucatan Peninsula today and will emerge into the Gulf of Mexico near Campeche this afternoon (see map).

At that point Dean is expected to be a Category 2 hurricane, with winds of at least 96 miles (155 kilometers) an hour.

The storm could regain strength, however, as it churns toward another landfall Wednesday afternoon about 160 miles (257 kilometers) east of Mexico City.

Forecasters think it will have winds of at least 111 miles (178 kilometers) an hour by then, making it a major Category 3 hurricane as it comes ashore again.

News reports attribute at least 12 deaths to Hurricane Dean since it began its trek across the Caribbean as a tropical depression on August 13.

(See photos: Hurricane Dean Lashes Jamaica.)

Forecasters had expected Dean to reach Category 5 strength sooner, but a phenomenon known as an eye wall replacement cycle kept the storm's winds below that threshold.

In this cycle a second eye wall forms around the storm's existing eye wall and acts as a noose, preventing the hurricane from intensifying. The event occurs only in very powerful hurricanes.

But as Dean approached the Yucatan Peninsula last night, it moved over heated waters and gained strength.

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