Tropical Storm Karen is poised to become the first named storm to hit the US during what had been a relatively quiet hurricane season.
Karen is forecast to lash the northern Gulf Coast over the weekend as a weak hurricane or tropical storm.
A hurricane watch is in effect from Grand Isle, Lousiana, to west of Destin, Florida. A tropical storm warning was issued for the Louisiana coast from Grand Isle to the mouth of the Pearl River, including the New Orleans area.
The National Hurricane Centre in Miami said early today that Karen was about 320 miles south of the mouth of the Mississippi River and had maximum sustained winds of 65mph with higher gusts.