Tropical Storm Karen

Tropical Storm Karen has developed over the Yucatan Channel and the southern Gulf of Mexico, and will ultimately pose a threat to the United States.

Hurricane watches are now in effect from Grand Isle, La., to Indian Pass, Fla. However, these watches do not include metropolitan New Orleans.

Tropical storm watches, however, do include metropolitan New Orleans, Lake Ponchartrain and Lake Maurepas, as well as the Gulf Coast from west of Grand Isle to Morgan City, La.

The disturbance had been festering over the past few days but until Thursday morning, Air Force reconnaissance aircraft were unable to find a closed circulation signaling the existence of a full-fledged tropical cyclone.

Data from Thursday morning's Air Force mission indicated that such a circulation had formed. Surface winds as high as 63 mph were initially measured in a portion of Karen's circulation, indicating that a fairly healthy tropical storm had formed. It is the Atlantic hurricane season's 12th tropical cyclone (including depressions) and 11th named storm.

As Karen moves north toward the central Gulf Coast, significant uncertainty remains about how strong it will become and how strong it can remain. Strong wind shear is expected to hold affect northern parts of the Gulf of Mexico, and this shear may cause Karen to weaken to some degree as it approaches the U.S. mainland.