A tropical depression churning in the southwestern Gulf of Mexico is expected to become the first named storm of the Atlantic hurricane season this weekend.
Heavy rainfall from the system began affecting oil rigs off the Texas coast Friday, an official at the National Hurricane Center said.
"The main threat now is heavy rainfall," said hurricane specialist Max Mayfield.
"Some of the rain bands are already up near the drilling platforms."
At 5 p.m. EDT Friday, the depression's center was near latitude 21.8 degrees north and longitude 93.4 degrees west, or about 380 miles southeast of Brownsville, Texas.
Its top winds were near 35 mph and it was expected to resume drifting to the northwest Friday night.
The system moved little Friday afternoon and was inhibited by Tropical Storm Beatriz in the Pacific Ocean off the coast of Acapulco, said Dan Guertin, forecaster for the National Weather Service.
"I can tell you the slower it moves and the longer it sits out there, the better the chance it can become a hurricane," Guertin said.
The depression formed near the Yucatan Peninsula, dumping heavy rains over eastern Mexico on Thursday.
Depressions are reclassified as tropical storms if sustained winds strengthen to at least 39 mph. A storm becomes a hurricane once its winds reach 74 mph.
The six-month Atlantic hurricane season began June 1.
The first tropical storm will be called Arlene.