Irene's potential threat to land was still uncertain, as its path had shifted east, according to forecasters at the National Hurricane Center in Miami. Forecasters said the storm could strike the coast anywhere from South Carolina to New Jersey.
"The people in the ... Mid-Atlantic states, from the Carolinas northward, should keep an eye on this, because there is a chance that in three to five days it could be close enough to be a threat," meteorologist Jack Beven told CBS Radio News.
Irene's top sustained winds increased to about 65 mph, and forecasters said the storm had strengthened Friday morning and conditions appeared favorable for the storm to strengthen further. Hurricanes sustain winds of at least 74 mph.
At 11 a.m. EDT, the storm's center was located about 300 miles south of Bermuda and about 700 miles southeast of Cape Hatteras, N.C.
It was moving northwest near 15 mph, though it was expected to slow down, forecasters said.
"The forecast track for the storm would keep it offshore, having it pass between Bermuda and North Carolina, and then moving in a general north-northwestward direction," said Beven.
Normally, there are only two named storms by this time in the Atlantic hurricane season. Irene became the earliest ninth named storm in the season, which began June 1 and ends Nov. 30, when it developed Sunday.
Earlier this month, the National Hurricane Center revised its earlier forecast and predicted an extremely active above-normal hurricane season for 2005, with nine to 11 hurricanes. The average is six per season. That would mean another seven to nine hurricanes before the season ends in November.