Tropical Storm Irene formed east of the Leeward Islands on Saturday and was expected to become a hurricane in the next two days heading on a northwestward track through the Caribbean that may threaten Florida.

At 11 p.m. (0300 GMT), Irene, the ninth named storm of the 2011 Atlantic hurricane season, was packing winds of 50 miles per hour and was about 95 miles east of Dominica, approaching the Leeward Islands, the U.S.-based National Hurricane Center said.

Tropical storm warnings were issued for many of the Leeward Islands, the Virgin Islands, Puerto Rico and the south coast of Dominican Republic, the center said after a U.S. Air Force Reserve hurricane hunter aircraft investigated the storm.

Some strengthening is forecast during the next 48 hours and Irene could become a hurricane on Monday, the NHC said.

Hurricane conditions are possible over the Dominican Republic by late Monday with tropical storm conditions possible by Monday afternoon, the Miami-based center added.

It would be the first hurricane of the so far busy, but to date not destructive, 2011 Atlantic hurricane season.

Computer forecast models showed Irene taking a northwestward path over Haiti and eastern and central Cuba and then heading up the western side of the Florida peninsula.

Depending on its eventual path and possible turns, Irene might still pose a threat to U.S. oil and gas installations in the Gulf of Mexico, but forecasters say it is too early to predict with certitude.

The NHC said that if Irene avoided land and stayed over warm Caribbean waters, conditions would be favorable for its strengthening. Almost all the guidance shows Irene becoming a hurricane in a day or two, it added.

Irene formed after Tropical Storm Harvey made landfall on the coast of Central America earlier on Saturday, lashing Belize with strong winds and rain and threatening to dump more on sugar- and coffee-producing areas in the region.

Late on Saturday, a weakening Harvey was bringing heavy rains to parts of Guatemala and eastern Mexico, the NHC said.

Mudslides and flooding could affect agricultural output in Central America, but this year's coffee and sugar harvests are largely complete.

The NHC said Harvey would continue moving inland across northern Guatemala and move into eastern Mexico on Sunday.

Harvey is expected to weaken to a tropical depression on Sunday and dissipate by Monday, the NHC said.

Forecasters said Caribbean island states, the Bahamas and Florida needed to closely monitor the path of Irene.

Given the uncertainties, this weekend would be a good time to go over your hurricane preparedness if you live anywhere in the Caribbean Bahamas, or Florida, since (it) could well be paying you a visit as a tropical storm or hurricane sometime in the next week, hurricane expert Jeff Masters of private forecaster Weather Underground wrote in his blog on Saturday.