Potential Tropical Cyclone Ten Update: Rain, Winds, Rough Surf for the Mid-Atlantic Coast Tuesday

Good afternoon! Our forecasting team continues to monitor Potential Tropical Cyclone Ten, currently sitting off the South Carolina coast. The system still looks lacks a well-defined center of circulation this afternoon. However, deep convection has increased around and east of the center. It still possible that storm will gain enough organization for it to be classified as tropical depression or Tropical Storm Irma tonight or Tuesday. Tropical Storm Warnings have now been issued for parts of the North Carolina coast.

The storm is still underneath some strong west-southwesterly shear. If this becomes a tropical cyclone, it’s unlikely that this system will intensify into a hurricane before becoming a non-tropical storm or Nor’easter by Tuesday night or Wednesday off the Delmarva. Regardless of classification, potential impacts are not likely to change along the Mid-Atlantic and Southern New England Coasts. Heavy rainfall will likely spread northward over Eastern North Carolina and Southeast Virginia later tonight. Rainfall totals between 2” to 4” with locally higher amounts are likely. East-northeast winds will likely gust to tropical storm force between 40mph and 60mph.

There is some uncertainty from this point forward regarding how far north the storm will track — and accordingly, the northern extent of heavy rainfall and tropical storm force winds.  Shortwave energy digging into the Ohio Valley is expected to interact with this storm and lead to some intensification. The storm is over the warmer waters of the Gulf Stream, so it may be able to obtain tropical characteristics. However,  mostly sheared vorticity and a broad upper-level trough suggest phasing will be slow and sloppy. This will keep the flow more southwest to northeast, with Potential Tropical Cyclone Ten or Irma moving out into the Western Atlantic on Tuesday and Wednesday.

NAM model show more phasing of robust 500mb shortwave energy, underneath a dual jet at 300mb leading caust track further north with more heavy rainfall.

NAM model show more phasing of robust 500mb shortwave energy, underneath a dual jet at 300mb leading cause more rainfall to spread northward.

However, with a dual upper-level jet streak, enough divergence of lift with tropical moisture, is likely to result in some moderate to heavy rainbands to spread northward into Maryland, Central and Southern New Jersey and Delaware by Tuesday afternoon and evening. Rainfall totals could be between 0.50” to 1.00”, with some locally higher totals again between 1” to 2”. The pressure gradient between high pressure to the north will also cause winds to increase to between 15 to 30mph with gusts up to 45mph possible, especially along the New Jersey shore.

Rainfall may continue spread as far north Southeast New York including New York and Southern New England by Tuesday night. But generally light rainfall totals are expected, high pressure will be stronger further north. Mostly cloudy, damp raw conditions are expected for tomorrow. Temperatures will likely not get out of 60s for much of the day. These temperatures are well below normal for the last few days of August.

RGEM models showing strong winds impacting Mid-Atlantic coast from North Carolina to Central New Jersey

RGEM model today showing winds around tropical storm force impacts parts of Mid-Atlantic shores from North Carolina to New Jersey

The storm will also generate swells with rough surf and rip currents along the coast. Worst conditions will be on Tuesday and Tuesday night. Some minor beach erosion is possible. But astronomically lower tides with the half moon phase will likely mitigate any serious coastal flooding issues. Check our ShoreCast page for more updates and information on weather and sea conditions tomorrow along the shores and beaches tomorrow.

This storm should move will be moving farther out into Atlantic on Wednesday. Any lingering clouds and showers during the morning, over coastal sections, should give away to more sunshine by the afternoon hours. Northwest downsloping winds should temperatures warm up back into mid-upper 70s. Surf along the shores will start to subside. But there could still be a high risk of currents and breezy conditions especially during the morning.

Stay tuned for premium and public updates tonight and tomorrow on this storm. You can also check the tropical weather dashboard for updates on more tropical potential and impacts with this storm.