Hundreds of National Guard troops were on alert and officials in the Carolinas warned residents to be ready for anything Wednesday as Ernesto — upgraded late Wednesday to a tropical storm — moved north away from Florida.

The National Hurricane Center in Miami estimated that Ernesto had maximum sustained winds of 40 mph east of the system's center.

Check the National Hurricane Center's forecast to monitor Tropical Storm Ernesto.

Forecasters said Ernesto could drench the eastern half of North Carolina with as much as seven inches of rain on Thursday and Friday. A separate storm system arriving ahead of Ernesto also threatened to soak the region.

Ernesto had weakened to a tropical depression while crawling north through Florida. Its winds were less a concern to emergency officials than the prospect of downpours.

Forecasters predicted the storm's center would be near the South Carolina coast late Thursday. From there, it was forecast to cut across the state's easternmost corner, then ride into central North Carolina.

A tropical storm warning remained in effect from Cocoa Beach, Fla., to the Wilmington area of southeastern North Carolina.

"We know we're going to get a lot of rain. We know this is going to be a water event," North Carolina Gov. Mike Easley said.

Easley activated 150 National Guardsmen and ordered the State Emergency Response Team to prepare for flooding and power outages. Guard troops in South Carolina were on standby, Lt. Col. Pete Brooks said.

North Carolina has struggled this summer with on-again, off-again drought.

"If we could get the rain where it was spread out over 12 to 24 hours, where it was a good, soaking rain, (flooding) would not be an issue," National Weather Service forecaster Phil Badgett said.

On James Island, one of a string of barrier islands on the South Carolina coast, Gerald Galbreath collected 24 sand bags. "It's just precautionary," he said.

At about 11 p.m. EDT, Ernesto was centered just north of Cape Canaveral, Fla., moving north at near 14 mph. The depression had winds near 35 mph, or about 4 mph below tropical storm strength.

As the storm passed over the Kennedy Space Center on Wednesday evening, NASA reported no problems.

The storm initially prompted NASA to start moving the space shuttle to its assembly building for protection, but the agency later reversed course and sent it back to the launch pad.

Little storm damage was reported in Florida, where Ernesto came ashore Tuesday night with a lot of rain but winds of only 45 mph.

"It was the little train that couldn't," said David Rudduck of the American Red Cross.

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