MIAMI (Reuters) - Sub-tropical storm Ana formed off the southeast coast of the United States with maximum sustained winds of 45 miles per hour (75 km/h), the U.S. National Hurricane Center (NHC) said late Thursday.
The first named storm of the Atlantic hurricane season was located about 170 miles (275 km) south-southeast of Myrtle Beach, South Carolina, the Miami-based federal weather forecaster said.
Ana, which began drenching the South Carolina coast with heavy rain on Thursday, is likely to strengthen into a tropical storm in the next day or so with winds of 50 miles per hour (81 km/h). It should remain near or over the warm waters of the Gulf Stream, the NHC said, before weakening as it approached the coast.
A tropical storm warning was in effect from Edisto Beach, South Carolina to Cape Lookout, North Carolina.
Ana's formation is the earliest appearance of a named storm in the Atlantic since a previous incarnation of Subtropical Storm Ana on April 20 2003, said Jeff Masters, chief meteorologist for Weather Underground, a commercial weather service.
The Atlantic hurricane season runs from June 1 through Nov. 30.
The Atlantic Ocean will see a "well below average" number of hurricanes this season due to cooler Caribbean waters and a strong El Nino effect, forecasters with Colorado State University predicted in April.
(This story corrects typo in last paragraph to refer to weather effect as El Nino not El Gino)
(Reporting by David Adams in Miami and Arpan Varghese in Bengaluru; Editing by Paul Tait, Gopakumar Warrier and Sunil Nair)
