Coastal storm brings risk of rainy, windy weekend to East Coast


A named storm might develop off the southeastern U.S. coast late this week, bringing gusty winds, rough surf, dangerous rip currents and heavy rainfall to the Eastern Seaboard into the weekend. Neither fully tropical nor entirely a run-of-the-mill mid-latitude storm, the possible hybrid system will feed off jet stream energy and the warm waters of the Gulf Stream.

There’s even a chance it earns the name “Ophelia,” though uncertainty about the storm’s expected path means it’s still not known what areas will be most affected.

It’s unclear how close to the coast the expected system will form, and subsequently how far inland its impacts will spread. That said, significant rainfall is possible for the Outer Banks, the Delmarva Peninsula and Cape Cod. A solid soaking is also possible for Washington, Philadelphia, New York and Boston, but these cities could also miss the bulk of the rain if the storm tracks more to the east.

There are also two other systems to track in the tropics, including Nigel, an ongoing hurricane that’s expected to stay west of the Azores, and another tropical wave that’s predicted to roll off the coast of Africa later on Wednesday. That one will probably develop and may whir disconcertingly close to the Lesser Antilles.

A possible subtropical storm

A stalled front draped across South Florida brought showers and thunderstorms to the peninsula for much of the first half of the workweek. A weak surface low will form along the front Thursday into Friday east of Florida and be energized by an approaching upper-air disturbance dropping out of the northwest.

That will intensify the surface low, which will blossom into a potential tropical-storm-force low as it meanders northeastward. It won’t be tropical, since it will have formed through nontropical processes. By Saturday though, it might start drawing upon the warm waters of the Gulf Stream, which would bolster convection, or thunderstorm activity, near the center. That would render the system “subtropical.”

Expected impacts

Regardless of the storm’s classification, its impacts will remain unchanged.

The storm will dump plenty of rain, with 3 to 5 inches possible within a two-day span where the heaviest rain occurs. The rain will affect the Carolinas on Friday, the Mid-Atlantic late Friday into Saturday and the Northeast over the weekend.

Onshore winds of 35 to 45 mph will buffet the coastline, with gusts near 50 mph possible in the coastal Mid-Atlantic if the storm jogs westward. The American GFS model simulates that this is in the realm of possibilities. In this scenario, gusts of 30 to 45 mph could extend as far west as the Interstate 95 corridor.

The storm may whip up waves of 25 to 30 feet just off the coast, which translates to near-shore rip currents and rough surf. Entering the water will be dangerous.

Areas of coastal flooding are also possible, especially around high tide.

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The strength of the system is in question, as is its eventual path. Both the American GFS and the European models indicate the storm will probably form Friday, but they then diverge markedly in their depictions of what will happen next.

The American GFS model simulates a stronger upper-air disturbance, which, in addition to making for a more intense surface low, will tug the storm farther west. That would lead to a possible landfall in the Mid-Atlantic and bring heavy precipitation farther inland. Washington, for example, would be absolutely drenched.

The European model, conversely, suggests that the parent upper-air disturbance will remain weaker. The storm system will still be waterlogged, but the upper-air disturbance won’t be able to pinwheel it back toward the coast. The result? A farther offshore track that only grazes the coastline, with a sharp cutoff to precipitation just inland. The nation’s capital would miss out almost entirely on rain.

It’s worth noting that some weather models, more seldom used — such as the Canadian model — project widespread significant rainfall along the Interstate 95 corridor. Again, that’s predicated on a stronger system taking a more westward track. We’ll be able to iron- out the details with greater confidence by late Thursday.

Other systems to watch

Elsewhere in the Atlantic, there are two other systems to watch. Nigel is a Category 1 hurricane about 650 miles east-northeast of Bermuda. It remains an “annular” cyclone, or one solid ring of thunderstorms surrounding an enlarged eye. It’s set to remain west of the Azores, then pass northward and dissipate before nearing Europe.

There’s also another tropical wave exiting the coast of Africa. The National Hurricane Center projects a 70 percent chance of eventual development. Weather models are bullish on its prospects for intensification into a named storm.

While odds favor it “recurving” northward before approaching the Lesser Antilles, at least some opportunity remains for it to shift farther south. That, in turn, could bring a greater risk for impacts to the Leeward Islands, but it’s too early to say anything definitively or to project its longer-term path.

Source: The Washington Post