Tropical Watch: Low off the Mid-Atlantic Coast

Good afternoon.

A relatively quiet weekend is underway in the Northeast, with little in the way of significant weather. There is a significant severe weather threat through Tuesday, but it should remain well south and west of the region (mainly in the Midwest and Southeast). The greatest area of interest, therefore, lies just offshore.

General Analysis

A low pressure area has developed about 150 miles offshore of Cape Hatteras over the Gulf Stream, and is currently producing a disorganized area of thunderstorms. Water temperatures there are certainly warm enough for development, with the sea surface temperatures generally in the 80-85F (27-29C) range over the Gulf Stream, although cooler water exists to the north and east. Wind shear is moderate (about 10 to 20 knots), but it is not inhospitable like it is in the Caribbean (which is why most forecasts are for a slow hurricane season overall). The National Hurricane Center (NHC) has tagged it as “Invest 92L” and currently estimates that it has a 20% chance of development into a tropical or subtropical cyclone, most likely in the next 24 to 36 hours if it does develop. I would personally estimate the chance to be somewhat higher, about 40-50%, given the model support it has.

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Sea surface temperatures off the Northeast and Mid-Atlantic coast. Notice the orange and red areas the low is currently over, and should remain over in the short term. Water warm enough for development reaches as far north as 39N latitude.

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Wind shear map at the upper levels. The low lies in an area of low to moderate wind shear, with higher (but decreasing) shear to the north.

Models are divided over this storm. The broader models don’t want to develop this system much, however, the mesoscale models seem to really be jumping on this one. In fact, some runs even produced a strong and well organized tropical storm SE of Long Island by late Monday. I wouldn’t rule out this possibility, but it is certainly not the most likely scenario. A weak, disorganized (sub)tropical cyclone is most likely. The next name on the tropical storm list is Claudette.

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WRF-ARW model run, courtesy of TropicalTidbits.com, valid for 8 pm EDT Monday evening . Notice a well organized tropical storm.

Impact Potential

The upper-level ridge over New England and eastern Canada, plus the incoming trough, should prevent this system from moving northward towards land. It would likely track eastward out to sea, with any land impact limited to the beaches. Surf levels may be higher than normal, and rip currents at the beaches also possible. However, the small size and distance from land should prevent any direct land impacts from this system. Offshore interests should be closely monitoring, however.

This is definitely a reminder that hurricane season is here, and early season impacts in the Northeast are rarely severe, but they do happen sometimes (example being Agnes in June 1972). Most severe Northeast hurricanes were from mid-August to early November. However, we always have to be on our toes – even in slow hurricane seasons. Most threats this year should be near shore due to a very hostile deep tropical environment, so watching our own backyards is critical. Remember that Bob in 1991 formed near shore (off the Florida coast) and rode the Gulf Stream as a strong hurricane.

Forecaster Craig Ceecee

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