Hurricane Wilma, churning in the northwestern Caribbean, will likely intensify during the next 24 hours and could threaten south Florida by the weekend as a major hurricane not unlike Katrina, according to meteorologists at the National Hurricane Center.

"There's an excellent chance Wilma will become a major hurricane," said Stacy Stewart, hurricane specialist at the National Hurricane Center in Miami. "We're not ruling out a Category 4."

Wilma, which was upgraded to a Category 2 hurricane this evening, is located about 185 miles south of Grand Cayman Island, with sustained winds of near 100 mph with higher gusts, according to an 8 p.m. EDT advisory by the center.

Reports from aircraft studying the hurricane show that Wilma's central pressure is falling rapidly, the center said, and the storm is "expected to become a major hurricane later tonight or on Wednesday."

Wilma is the 12th hurricane and the 21st named storm of the season. This is only the second season in history with that many named storms.

Stewart said conditions in the Caribbean -- mainly very warm ocean temperatures and favorable winds in the upper atmosphere -- are conducive to a rapid intensification of the storm.

The storm is drifting slowly toward the west-northwest, according to the advisory. And a continued slow motion in the same direction is expected during the next 24 hours.

Stewart said a turn to the northeast toward the western Florida coast is likely by Friday. He said that on its present course, Wilma could make landfall by Saturday along the Florida coast anywhere from the Keys to the Tampa area.

"The Florida peninsula should closely monitor the progress of Wilma," the advisory said.

Hurricane winds extend outward up to 15 miles from the storm's center and tropical storm winds extend up to 140 miles out, the hurricane center said.

Wilma is expected to produce 5 to 10 inches of rainfall over the Cayman Islands, Jamaica, Haiti and southeastern Cuba with up to 15 inches of rain possible in some areas, according to the advisory.

Oil markets have been jittery watching the storm's progress, afraid that it could strike the devastated Gulf Coast refineries, which are still struggling to get up to full capacity after hurricanes Katrina and Rita. Gas and crude oil prices rose yesterday on concerns Wilma could veer toward the Gulf Coast. But the threat to energy seems to have abated today with the storm's progress now toward Florida.

Wilma exhausts this year's list of storm names. Any additional storms and hurricanes that form this season will be named using the Greek alphabet, beginning with Alpha.

Four storms have formed this month, double the October average of two storms. Six is the record for October, set in 1950 and 1887, according to the hurricane center.

Hurricane specialist Stewart said the Atlantic Ocean is currently in an active 30-year hurricane period, which started in 1995. He said the recent stepped-up activity is not unusual for an active period.