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Coastal storm update: More heavy rain, wind tonight

A coastal storm, developing as a result of a powerful mid and upper level system, developed today from the Delaware Coast to a position off the coast of the Mid-Atlantic states. Heavy rain moved through much of the area as a result of an inverted trough, and shifted from north to south throughout the day as the surface low moved more seaward. Since then, precipitation has become much more showery in nature — absent are the areas of heavy rain and thunderstorms. Northeasterly winds have increased in intensity along the coast.

Through the evening, the surface low off the coast is expected to strengthen slightly as the mid and upper level systems move south of Long Island. In a form more typical to winter-time systems, the surface low may actually hook back westward later tonight. While the storm itself isn’t necessarily strong in regards to its central pressure, the gradient between the developing surface low and the higher pressures around it will aid in the development of strengthening surface winds, especially along the coast.

With the surface low moving back westward a bit, forecast models indicate increased lift and the potential for another period of very heavy rain. The latest HRRR and high resolution NAM models actually back the surface low over parts of Western Long Island, bringing winds over 40 miles per hour and heavy rain with thunderstorms. This increased lift may spread westward over time, moving over New York City and New Jersey tonight into the early morning hours of Thursday.

Simulated radar on the HRRR model overnight tonight into Thursday morning.

Simulated radar on the HRRR model overnight tonight into Thursday morning.

While the HRRR may be somewhat overdone in its depiction of the surface low track and surface winds, the mid level height pattern argues that the system may very well bring another period of heavy rain to our area. A closed 500mb low will move south of Long Island tonight into Thursday, and a closed 700mb low will travel along a path which has historically brought our area very heavy precipitation. If the surface low does back westward a bit as modeled, another period of moderate to heavy rain is very likely tonight.

NAM 500mb forecast showing a closed low south of Long Island tonight.

NAM 500mb forecast showing a closed low south of Long Island tonight.

The winds which develop will depend greatly on any developing convection, and the exact track of the storm itself. It will be up to convection to mix down stronger winds which are just above the surface. Still, moderate wind gusts will be possible as the surface low comes closer to our area and the pressure gradient tightens. Northeast winds will become very gusty tonight, especially along the area beaches.

Stay tuned over the next few hours for updates, including a possible live blog where our meteorologists will update information on the Nor’Easter this evening.

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