Disruptive coastal storm to bring tropical storm conditions from the Carolinas to mid-Atlantic

Subtropical development possible with newly minted Invest 99L, but regardless gusty winds, heavy rain, rough seas and coastal flooding expected beginning tomorrow

Thursday morning satellite of newly designated Invest 99L off the southeast U.S. coast. Credit: NOAA.

It may or may not garner a name, but the coastal storm developing off the southeast U.S. today (now designated Invest 99L by the National Hurricane Center) will bring tropical storm conditions to a wide stretch of shoreline from Myrtle Beach northward through the Outer Banks and into the Virginia Tidewater starting tomorrow into Saturday.

While the NHC gives the area a medium chance of developing into a named subtropical storm, whether it does so will have little bearing on coastal impacts. Wind gusts of 40-50 mph will churn up seas and the strong onshore winds are expected to produce areas of minor to moderate coastal flooding, especially around the times of high tide. The coastal flood threat will be greatest from the Outer Banks into the lower Chesapeake from Friday afternoon through Saturday but could extend up to the southern New Jersey coast by Saturday afternoon and evening.

The heaviest rainfall with the storm will be confined to the immediate coastal areas in eastern North Carolina and along the Delmarva. Rain totals up to 4-6 inches could cause localized flash flood issues, especially in lower lying areas. The storm, while disruptive along the coast and dangerous for those on or in the water, isn’t expected to produce widespread damage inland.

Whether or not the system can gather enough characteristics to be deemed subtropical will hinge on how much of a convective boost it can get from the nearby Gulf Stream tomorrow. We’ll be watching for more consolidated storminess near the low-pressure center rather than away from the center as is typical for non-tropical storm systems.

Invest 99L is not a threat to South Florida.

Watching the westward trends in the Atlantic for next week

The disturbance we’ve been following off Africa is showing some signs of organization today. The system isn’t expected to develop quickly but has a high chance of becoming a named storm by next week.

The models have trended west with the system, which means those in the islands will need to pay closer attention to this for next week.

Low pressure tracks from the European ensemble modeling system through next Wednesday evening, September 27th. Model guidance suggests a strengthening tropical cyclone approaching the islands for mid-week. It’s too soon to know if the system will bend north before or after reaching the Lesser Antilles so interests in the islands should closely monitor the forecasts. Credit: Weathernerds.org

Right now, forecast guidance shows a bend northward very near the islands around mid-week. It’s too far out to know whether this will happen before or after it reaches the Lesser Antilles, but regardless, models are on board with a strengthening tropical system approaching the Leeward Islands by next Tuesday into Wednesday.

Nigel accelerating into the far North Atlantic

Hurricane Nigel has persisted against increasingly hostile upper-level winds as it accelerates into the far North Atlantic. The hurricane is expected to transition into an extratropical cyclone by later today or tomorrow and become absorbed by a much larger North Atlantic storm system over the weekend.

About the Author:

Michael Lowry is Local 10's Hurricane Specialist and Storm Surge Expert.