for National Geographic News
The Gulf Coast's fate depends largely on a developing high-pressure system, whose southern edge extends roughly from the eastern Gulf of Mexico to the western Atlantic Ocean. (See a map of the region.)
High-pressure "ridges" repel storms, so if the developing ridge north of Cuba is strong, Gustav could be deflected westward and into the central Gulf of Mexico, where vast stretches of warm water could supercharge the storm as it heads for the U.S. coast.
But if the high-pressure system wanes, Gustav could turn north, unimpeded, and move overland, across Cuba. The temporary lack of contact with warm water would deprive it of power.
From Storm to Hurricane to Storm to Hurricane?
Gustav began as a tropical depression in the eastern Caribbean Sea on Monday and quickly intensified into a Category 1 hurricane with winds of about 90 miles (145 kilometers) an hour.
Gustav hit shore Tuesday in Haiti and has been blamed for at least 17 deaths there and the neighboring Dominican Republic.
The passage over Haiti's mountains weakened Gustav's winds to about 60 miles (100 kilometers) an hour, reducing it to tropical storm status.
As of Wednesday morning, the center of Gustav was nearly stationary over Haiti. But the storm is expected to start moving westward later in the day. That would put it over the very warm waters of the Caribbean, and forecasters think Gustav will quickly regain its status as a Category 1 hurricane, with wind speeds between 74 and 95 miles an hour (119 and 153 kilometers an hour).
By early Saturday, Gustav is predicted to be just off the coast of western Cuba as a Category 3 hurricane, with winds between 110 and 130 miles (177 and 209 kilometers) an hour.
Where it goes from there—and how intense it becomes—is less certain.
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