Tropical Storm Bill became the first hurricane of the 2009 Atlantic season on Monday but remained far from any land, the US National Hurricane Center said.
Bill's sustained winds reached to nearly 120 kilometres per hour as it churned through the Atlantic Ocean more than 1,870 km east of the Lesser Antilles islands of the Caribbean, the hurricane center said.
Earlier Monday morning Tropical Storm Claudette moved ashore along the US Gulf coast.
Claudette, which formed early Sunday morning, hit the coast near the eastern end of Santa Rosa Island, just southeast of Fort Walton Beach, Florida, at 1:10 am EDT (local time), the hurricane center said.
The six-month Atlantic hurricane season got off to a slow start with no storms in the first 2-1/2 months but exploded this weekend as three tropical storms formed in just over a day.
Bill is expected to strengthen, and forecasters now expect it to whip up into a "major" Category 3 hurricane by Wednesday, with winds of more than 177 kph. Some computer models suggested Bill could reach Category 4, with winds of more than 210 kph.
Hurricanes of Category 3, 4 or 5 on the Saffir-Simpson intensity scale are the most destructive type.
Bill is advancing quickly west-northwest near 35 kph, and this is expected to continue for the next 24 to 48 hours.
Strike the US Saturday
On its most likely track, Bill would be well north of the northernmost Caribbean islands, while heading toward the US East Coast and striking by Friday, forecasters said.
Claudette had swept through the Gulf of Mexico but bypassed the heaviest concentration of US energy platforms, which stretch along the coast from Mobile Bay, Alabama, to Brownsville, Texas.
The Gulf is home to almost half of US refinery capacity, a quarter of oil production and 15% of natural gas output. Oil companies were monitoring the storm but had not shut down production.
Claudette packed sustained winds of 80 kph as it swept over the Florida panhandle and is is seen reaching southern Alabama, when it will likely weaken to a tropical depression, the Hurricane Center said.
Early on Monday, Tropical Storm Ana, which had faded to a tropical depression on Sunday and was expected to weaken further, was moving quickly west-northwest across the northeastern Caribbean sea.
Ana is forecast to cross the coast of the Dominican Republic later Monday with maximum sustained winds near 55 kph.