Want rain? Ernesto's on its way to deliver

Storm could dump 5-10 inches on Md.

August 31, 2006|By Frank D. Roylance | Frank D. Roylance,Sun reporter

You prayed for rain to end the drought and water the tomatoes. But not this. And surely not at the start of the long Labor Day weekend.

Ernesto, which fizzled in Florida, is bearing down on Maryland with what forecasters say could be half a foot or more of rain, flash floods, bay shore flooding and even a tornado before the tropical storm begins to clear the region Saturday.

"Right now we're anticipating 5 to 10 inches of rain as a broad forecast for the region," said David Manning, warning coordinator for the National Weather Service's forecast office in Sterling, Va. "Tropical systems are very efficient rain producers."

On top of that, persistent winds from the east or southeast will pile water into the Chesapeake and its western shore today and tomorrow, coinciding with the rain. But it should not approach the 8-foot storm surge that caused extensive damage around the bay during Tropical Storm Isabel almost three years ago.

"A few gusts of 40 to 50 mph are not out of the question," said Jeff Warner, a meteorologist with the Penn State Weather Communications Group in State College, Pa.

Yesterday, a coastal flood watch was issued for late tonight through late tomorrow night. A flash flood watch was posted for most of Maryland and Virginia for this afternoon through late tomorrow.

The beach resorts could see rough surf and beach erosion going into the holiday weekend, as strong easterly winds push water onto the shore.

To the south, hurricane-weary Floridians caught a break as Ernesto came ashore there yesterday. Parts of the state got several inches of rain. Car accidents on wet roads caused at least two deaths, and several thousand customers lost electric service.

But winds at landfall on Marathon Key barely topped 45 mph, and damage was slight.

Ernesto moved off the northeast Florida coast overnight, regaining some strength over the Atlantic, and was expected to come ashore again today in the Carolinas and head overland toward Canada.

Several factors are expected to combine to bring far heavier rainfall to the mid-Atlantic states as Ernesto passes through, Warner said.

The first is an "old" cold front that finally slid down across Maryland yesterday, dropping daytime highs in Baltimore from the 90s on Tuesday to the 70s yesterday.

Ernesto's warm and very moist air mass will push north ahead of the storm itself, colliding with the cold front to our south. The warmer tropical air will ride up over the denser cold air, cooling and condensing its water vapor and triggering heavy rain, Warner said.

Then the storm's center has to move through, he said. Precisely where it will take its heaviest rain is uncertain. Up the Appalachians into West Virginia is most likely, Warner said, "but southeastern Virginia or southern Maryland are not out of the question."

Forecasters typically have a lot of difficulty forecasting the intensity of tropical storms. Warner predicted less rainfall from the system than the weather service: 2 to 3 inches, with isolated spots seeing up to 10 inches.

Up to 7 inches of rain was forecast for North Carolina.

Manning said flash flooding is possible where rain rates and runoff exceed the capacity of local rivers and streams. That's where this summer's scant rainfall will help - leaving room in streambeds for the new rain.

It could take the main stems of such rivers as the Susquehanna and the Potomac several days to feel the storm's full effects, he said. But "small streams and creeks definitely have the potential for flooding."

Ernesto's track north was expected to take its center west of the Chesapeake, the same track Tropical Storm Isabel took in 2003 and which contributed to the disastrous storm surge that swamped bayside communities.

That's because tropical storms rotate counterclockwise. When they track west of the bay, the spin brings winds up the bay from the south or southeast, piling water up in rivers and creeks.

But, aside from its predicted path, Ernesto bears little resemblance to Isabel, forecasters said.

Isabel grew unfettered at sea into a Category 5 storm - with top sustained winds of 166 mph before it weakened and came ashore as a Category 2 hurricane.

Ernesto was a hurricane for just a few hours Sunday in the Caribbean and had weakened to a tropical depression while crawling north through Florida.

Although it regained tropical storm strength (40-mph winds) last night as it moved north away from Florida, Ernesto will likely be a tropical depression again before it reaches Maryland, forecasters said.

The coastal flooding danger, they said, arises from a combination of Ernesto's winds and low pressure, and a strong high-pressure system centered over Quebec and New England.

As the atmosphere seeks to equalize that pressure difference, it will set up a strong, persistent easterly wind flow in the mid-Atlantic states today and tomorrow.

"Winds from the east will certainly drive water up into some of the channels, such as the Potomac, on the west side of the bay," Warner said. "That's not necessarily a true storm surge, but it will have that effect."

"We're not expecting anything on the order of Isabel," Manning said. "This is a different scenario, kind of on the order of what we can get from a nor'easter in the wintertime."

Tornadoes are also a hazard wherever tropical storms are decaying. The highest risks are on the right side of the storm - in this case east of the storm's path.

"There's going to be a lot of hazardous weather Friday into Friday night," Manning said. "Everyone should be mindful and listen to local media and the weather service and be ready to take action if bad things happen."

frank.roylance@baltsun.com

The Associated Press contributed to this article.

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