(CBS/AP) Wilma, the record-tying 21st tropical storm of the season, formed in the Caribbean on Monday, and forecasters warned it could become a powerful hurricane and hit somewhere along the U.S. Gulf Coast as early as the weekend.

"I think the message is that the season is certainly not over. People in the Gulf Coast are going to have to watch Wilma," said National Hurricane Center Director Max Mayfield. The Atlantic hurricane season runs from June 1 to Nov. 30.

Wilma is the 21st named storm of the season, tying the record for the most storms in an Atlantic season. The only other time that many storms formed since record keeping began 154 years ago was in 1933.

At 2 p.m. EDT, Wilma had sustained winds of 50 mph, up 10 mph from earlier in the day, and was centered about 235 miles southeast of Grand Cayman. It was drifting southward but was expected to turn toward the west.

A hurricane watch was issued for the Cayman Islands, meaning hurricane conditions could be felt there within 36 hours. A tropical storm warning, meaning tropical storm conditions are expected within 24 hours, also was posted. A tropical storm warning was also issued for the Honduran coast.

The storm is expected to bring 4 to 6 inches of rain in the Cayman Islands and Jamaica, with as much as 12 inches possible in some areas, National Hurricane Center forecasters said.

"We're on alert but we're not panicking," said Tootie Eldemire, owner of the Eldemire Guest House on Grand Cayman.

"We will have to watch this storm, because later in the week and over the weekend, it could be trouble in the Gulf of Mexico," said CBS News Meteorologist George Cullen. "All indications are that it will probably pass along the shores of the Yucatan Peninsula ... It will probably become a hurricane."

But hurricane specialist Stacy Stewart said Wilma had shifted west of its previous path and could hit Mexico's Yucatan Peninsula, not the U.S. Gulf Coast. "At this time it doesn't appear it will be a major threat to the United States during the next five days," Stewart said.

Larry Lahiff, a meteorologist at the National Hurricane Center, warned that Wilma's path was still uncertain even if it reaches the Gulf: "Usually when a storm gets into the Gulf, it's going to hit somewhere. Where, that's too early to tell right now. Some models take it west, some take it north."