MIAMI The 14th tropical storm of the Atlantic hurricane season faded rapidly on Monday but two new tropical systems developed in the Caribbean, threatening Puerto Rico, the Virgin Islands and also Central America.
Tropical Storm Nana, which developed on Sunday roughly midway between the Cape Verde Islands off Africa and the Caribbean, succumbed to adverse atmospheric conditions and weakened into a tropical depression on Monday morning.
It was expected to dissipate "within a day or so," the U.S. National Hurricane Center said.
The 15th tropical depression of the season, meanwhile, formed around 340 miles southwest of San Juan, Puerto Rico, the Miami-based hurricane center said.
It was expected to drift northwestward for a while before strengthening into a tropical storm and getting the name Omar, and would then shoot off to the northeast near Puerto Rico and potentially grow into a hurricane over the open Atlantic.
Neither the remains of Nana nor the new tropical depression were considered a threat to the United States or the oil fields of the Gulf of Mexico.
However, a third tropical weather system was developing in the western Caribbean off the coast of Nicaragua and could affect Central America, Mexico's Yucatan Peninsula, the Cayman Islands or western Cuba, U.S. forecasters said.
If that system strengthened into a tropical storm with winds of at least 39 miles per hour (63 km per hour), it would be called Paloma.
The 2008 hurricane season has lived up to forecasts that it would be a busy one. An average season spawns 10 storms, of which six strengthen into hurricanes.
The United States, in particular, and the oil fields off the coasts of Louisiana and Texas, have been in the firing line this year. Hurricane Gustav slammed ashore near New Orleans, the city devastated by Hurricane Katrina in 2005, and Hurricane Ike hit Houston.
It has also been a deadly season for Haiti, where more than 800 people were killed as the impoverished Caribbean nation was swamped by Fay, Gustav, Hanna and Ike, and a damaging season for Cuba, which was raked by Gustav and Ike.