MIAMI - Tropical Storm Barry formed in the Gulf of Mexico on Friday _ the first day of hurricane season _ and the National Hurricane Center issued a tropical storm warning for a stretch of Florida's western coast.

The storm was centered about 320 miles southwest of Tampa and about 235 miles west of Key West at about 8 p.m. It had sustained winds near 50 mph and was moving north near 12 mph. Forecasters expected Barry to gradually turn north-northeast and increase in speed over the next day, though no significant change in strength was anticipated before possible landfall.

"We're not looking for a hurricane," said Dave Roberts, a hurricane specialist at the Hurricane Center.

Word of the storm's development came on the first official day of a hurricane season that forecasters have said they expect to be busier than normal. The National Weather Service said it expects 13 to 17 tropical storms, with seven to 10 becoming hurricanes and three to five in the strong category.

Roberts said it was "coincidence, maybe," that the storm formed on the first day of the season.

Forecasters issued a tropical storm warning, meaning tropical storm conditions are expected in the next day, for the Gulf Coast from Bonita Beach, Fla. to Keaton Beach, Fla. A less severe tropical storm watch, meaning such conditions were expected within 36 hours, was issued from north of Keaton Beach to St. Marks.

The hurricane center said Barry threatened to bring dangerous battering waves, coastal flooding up to 5 feet and rainfall of 3 to 6 inches in the Florida Keys up through southeast Georgia.

"The rainfall already began," said Lixion Avila, a hurricane specialist. "It's part of the system. ... The strongest bands are over the Keys, western Cuba and the over the Gulf of Mexico."

The tropical weather wasn't expected to ease drought conditions much in Florida, which is facing one of its driest years on record.

"It'll help a little bit, but everyone is so far below rainfall that we're still going to be under drought conditions," said Kim Brabander, a meteorologist with the National Weather Service. "To really alleviate the drought conditions, we're going to need anywhere from 30 to 40 inches of rain."

Tropical Storm Barry formed more than three weeks after the first named storm of the year _ Subtropical Storm Andrea _ developed off Florida's eastern coast. Andrea skirted the southern Atlantic coast but caused minimal damage.

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Associated Press writer Jessica Gresko contributed to this report.