Tropical Storm Harvey is now drifting over the Gulf of Mexico about 90 miles east-southeast of Port O'Connor, the National Hurricane Center said.

It will meander over the Gulf on Tuesday before making a final landfall somewhere near the Texas/Louisiana border, likely on Wednesday.

Harvey is then expected to slowly move northeast across Louisiana and Arkansas as a tropical depression from Thursday into Saturday.

TUESDAY: Here's where Harvey is headed

As it spins offshore, the storm is expected to dump an additional 7 to 13 inches of rain through Friday over the upper Texas coast and into southwestern Louisiana, exacerbating the life-threatening, catastrophic flooding in the Houston area, the hurricane center said.

Isolated storm totals may reach 50 inches over the upper Texas coast, including the Houston/Galveston metropolitan area.

In the past four days, the weather service forecast office in Houston has picked up over 42 inches of rain.

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Since Friday, an average of 26 inches of rain has fallen in Harris County, where Houston is located, the Weather Channel said.

That much rain would provide drinking water for the entire county for roughly five years. Harris County is home to 4 million people, making it the third-largest county in the U.S.

Brief tornadoes may also form anywhere from Galveston eastward to just south of New Orleans, the National Weather Service warned.

As of 7 a.m. CDT, Harvey had maximum sustained winds of 45 mph with a few higher gusts reported. It was moving to the east-northeast at 5 mph.

Forecasters were also monitoring another system off the Carolina coast, which is bringing rain to the mid-Atlantic on Tuesday morning.

Still another system is being watched in the eastern Atlantic Ocean, which has an 80% chance of becoming a tropical depression or storm in the next five days.