forNational Geographic News
Hurricane Gustav had the potential to become a monster hurricane last Saturday, but two factors intervened to keep it from intensifying.
The hurricane's passage over western Cuba "roughed it up" just enough so that the storm's eye partly deteriorated, said Jeff Masters, director of the private forecasting service Weather Underground in Ann Arbor, Michigan.
And upper-level winds—known as wind shear—were just strong enough to keep the hurricane from quickly regaining power over the very warm waters of the Gulf of Mexico, he said.
The hurricane struck Cuba Saturday with peak winds of about 150 miles (241 kilometers) an hour.
"If the shear had been [a little weaker], it would have survived the crossing of Cuba without undergoing a major disruption," Masters said.
"It would have intensified into a Category 4 hurricane and been a disaster [for the U.S.] We got lucky." (See photos of Gustav barreling into the Gulf.)
Category 4 hurricanes have winds ranging from 131 to 155 miles an hour (211 to 249 kilometers an hour).
When a disrupted Gustav crossed an area of very warm and deep water in the Gulf of Mexico known as the Loop Current, it was not able to restoke its energy.
Once it was past the Loop Current, Gustav entered cooler, shallower water closer to the Gulf Coast and began losing power.
The hurricane came ashore in Louisiana yesterday morning as a strong Category 2 storm with winds of 110 miles (177 kilometers) an hour.
Gustav was just below the threshold of being classified as a major hurricane with winds of 111 miles (179 kilometers) an hour.
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