12:15 PM | ****East coast tropical storm to be impactful all the way from the Carolinas to southern New England…heavy rain, strong winds, coastal flooding, rough surf…all on the table****

Low pressure is beginning to form over the southwestern Atlantic Ocean along a frontal boundary zone. There is even the beginnings of a “swirl” in the cloud pattern over this part of the Atlantic Ocean which remains at very warm levels. This tropical storm will intensify during the next 24-48 hours as it heads in a general northward direction. It will take on tropical characteristics and can become a named tropical storm (would be “Opehia”) and has an outside chance of reaching category 1 hurricane status. Images courtesy NOAA (GOES-East)

Overview

A storm is beginning to take shape today over the southwestern Atlantic Ocean where sea surface temperatures remain at unusually warm levels as high as 30 degrees (Celsius). This developing system will take on tropical characteristics and move in a general north-to-northwest direction over the next couple of days. Later in the weekend, this storm is likely to slow down some as it makes a turn from a northerly direction to northeast. Whether or not it becomes a named tropical storm by NOAA’s National Hurricane Center (and there is an outside chance of it reaching category 1 hurricane status), this system will be quite impactful in terms of rain, wind and surf all the way from the Carolinas to southern New England.

Winds can gust to 50+ mph along coastal sections from the southern Mid-Atlantic-to-Long island-to-southern New England and potentially to 60+ mph along the Carolina coastline depending on the rapidity of the intensification. Map courtesy ECMWF (00Z Euro), Weather Bell Analytics (Meteorologist Joe Bastardi, Twitter)

Details

Typically, the second half of the Atlantic Basin tropical season features more in the way of tropical systems that develop relatively close to the US rather than the “long-tracking” waves that come off Africa’s west coast such as what took place recently with Hurricane Lee. These “nearby” tropical systems can form closer to the US in locations like the Gulf of Mexico, Caribbean Sea or the southwestern Atlantic Ocean where sea surface temperatures remain very warm and are currently as high as 30 degrees (C). Indeed, a storm is beginning to take shape today off the Southeast US coastline and it is likely to take on tropical characteristics as it should spend quite a bit of time over the open warm waters of the SW Atlantic (tropical characteristics meaning it’ll evolve into a “warm” core system up to mid-levels of the atmosphere). Whether or not this system is ultimately officially deemed “tropical” and named by NOAA’s National Hurricane Center remains to be seen. (If it does become a named tropical storm by NOAA, it would be “Opheila” and there is an outside chance it reaches category 1 hurricane status).

Sea surface temperatures remain very warm across the Gulf of Mexico and the southwestern Atlantic Ocean which is where tropical low pressure will intensify over the next 24-36 hours. In fact, temperatures are as high as 30 degrees (Celsius) in the Gulf and in this part of the Atlantic Ocean - plenty warm enough for development and intensification of a tropical system. Map courtesy NOAA, tropicaltidbits.com

On Friday, strong and intensifying high pressure will shift to eastern New England at the same time the tropical low pressure system intensifies off the Carolina coastline. The pressure gradient between the strong high pressure system to the north and the intensifying tropical storm to the south will tighten and surface winds will respond by strengthening; especially, along coastal sections. Those strengthening onshore winds (E-NE direction) will be persistent for an extended period of time and this will result in beach erosion, rough surf, and likely coastal flooding at times of high tide all the way from the Carolinas to southern New England. Winds can gust to 50+ mph in coastal areas from the southern Mid-Atlantic-to-Long Island-to-southern New England and potentially to 60+ mph along the Carolina coastline depending on the rapidity of the intensification of this storm before landfall (and I think it will be rapid).

This storm will likely make landfall sometime early Saturday in the eastern part of North Carolina classified as a strong tropical storm or perhaps as a category 1 hurricane (if deemed tropical in nature by NOAA’s NHC). By late Saturday/early Sunday, the storm will tend to slow down some as it reaches the Chesapeake Bay region and turn from a northward direction to northeast and it’ll continue to slowly weaken from its peak strength reached just before landfall.

Total precipitation amounts for the upcoming tropical weather event as depicted by a blend of computer forecast models. Map courtesy Pivotal Weather, NOAA

In the immediate DC-to-Philly-to-NYC corridor, rain and wind will become issues later tomorrow night and continue through much of the weekend as the system will slow down upon reaching the Chesapeake Bay. The rain can be heavy at times this weekend with a few inches on the table, but it is not likely to be raining all the time. Indeed, as it pretty typical with tropical systems, rotating bands of rain are likely to develop meaning it can rain hard for awhile in a given location, slacken off to little or nothing, and then return back to bursts of heavy rain. One final note, it is still a little difficult to determine how far to the north and west this coastal storm’s rain shield will end up going on Saturday (i.e., how far inland). However, it is looking increasingly likely that it’ll push all the way into eastern West Virginia and central Pennsylvania which certainly can have an impact on Penn State’s (night) game in University Park where it is looking wet and quite chilly.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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