Tropical Storm Bertha menaces US Gulf Coast

July 21 (Reuters) - Tropical Storm Bertha churned across the northeastern Gulf of Mexico on Tuesday, bringing tropical storm conditions toward the northern U.S. Gulf Coast, while a separate weather system threatened severe thunderstorms and heavy rain across the U.S. Northeast.

Bertha, the second named storm of the Atlantic hurricane season, was centered about 90 miles (145 km) southwest of Panama City, Florida, as of 1 p.m. CDT (1800 GMT), according to the National Hurricane Center, packing maximum sustained winds of 60 mph (95 kph) and moving northwest at 5 mph, the hurricane center said.

Forecasters said the storm was beginning a turn westward and was expected to move near or along the northern Gulf Coast through midweek. A gradual weakening was forecast on Wednesday through Friday.

Tropical storm warnings stretched from Florida's Panhandle westward into coastal Louisiana, with watches extending into the New Orleans area. The hurricane center warned of dangerous surf and rip currents for summer vacationers.

The National Weather Service said tropical storm conditions were expected to spread across portions of the coast from the Florida Panhandle to southeastern Louisiana later on Tuesday and Wednesday.

Chevron CVX.N said it was shutting in production at its Petronius facility in the Gulf as a precaution, and all associated personnel were being moved onshore in preparation for the storm. The U.S. oil major also said it was transporting nonessential personnel from its two other platforms.

The main threat from Bertha was expected to be heavy rainfall and localized flooding. Forecasts called for several inches of rain along parts of the central Gulf Coast from western Florida to southern Louisiana through Thursday.

Farther north, the National Weather Service warned that numerous severe thunderstorms were expected from the Ohio Valley into the Mid-Atlantic and Northeast states. Forecasters said swaths of damaging wind gusts were likely, and some tornadoes could develop as the storms tracked eastward.

A tornado watch was issued for New York City for Tuesday night.

The storm system was also forecast to bring periods of heavy rainfall to parts of the Northeast, increasing the risk of flash flooding in areas already saturated by recent wet weather. Emergency managers urged residents in both regions to monitor local forecasts and heed warnings as conditions evolved.

(Reporting by Daniel Trotta in Vista, California
Editing by Rod Nickel)

((daniel.trotta@reuters.com))