marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 233 am EST sun Nov 19 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Over the short term, gales will continue to overspread most of the offshore waters this morning as a strong cold front reaches the E coast by around 12z, and then slides E and se over the waters throughout today, passing E and se of the area tonight. An ascat pass from last evening around 0238z indicated SW gales just off the Delmarva coast, which is in good agreement with the latest grids and 00z GFS guidance. We will maintain storm warnings for portions of the northern nt2 waters today, which will also maintain forecast continuity. We still expect storm force winds to develop over the offshore zones of anz920 by around 18z today, and the outer zones of anz905 and 910 by later today with these zones remaining close to the north wall of the Gulf Stream and near a strong low-level jet, and also in the vicinity of thunderstorms that will form near and in advance of the strong cold front. Thunderstorms are most likely from southern nt1 waters southward over nt2 waters today into this evening per the latest sref thunderstorm guidance. Very gusty winds and very rough seas are likely in and near any of the stronger thunderstorms. Slowly improving conditions are expected tonight into Tue as high pressure slowly builds E over nt2 waters later Mon into early Tue. Gales are still forecast to briefly end over the waters early tonight, and then re-develop once stronger cold air advection develops later tonight into Mon night mainly over nt1 and northern nt2 waters, or similar to the past few opc forecasts. As the high moves E of the waters by later Tue a return to S and SW winds is forecast to develop over the offshore waters with the next cold front moving E and se from the eastern Great Lakes.
Short term model preference...the 00z GFS and continued use of the smart tool placing the higher first sigma layer winds over the unstable areas and lower 10 meter winds over the stable areas for today through Tue. Confidence levels somewhat above average.
Over the medium range, the 00z GFS and 00z ECMWF are coming into better agreement over the region for Tue night into Wed night. A cold front will move se over the waters Tue night as low pressure forms along the front off the S and N Carolina coasts. The low will slowly develop and track NE over the eastern portions of the nt2 waters Wed. At this time, we feel confident enough to add minimal gales to the eastern or outermost nt2 waters beginning Tue night, and then moving NE with the low toward NE nt2 waters Wed, moving E of the waters Wed night as the low moves further E. For now we will cap winds at 35 kt over these waters Tue night through Wed, and continue to evaluate future models cycles and adjust the forecast as needed. By Thu and Thu night the 00z models are a little stronger and a little further W with low pressure moving NE toward the southern nt2 waters from near Florida. For now, we will return to the previous grids and 12z ECMWF guidance from yesterday for the forecast for Thu and Thu night, and adjust the forecast over the next few days as guidance comes into better agreement.
Medium range model preference...00z ECMWF Tue night into Wed night, with winds capped at 35 kt. Thu and Thu night...previous grids or close to the 12z Sat ECMWF guidance. Some manual edits to blend the forecast and grids with nearby coastal WFO and TAFB grids. Confidence levels slightly below average.
.Seas...We will stay close to the previous sea height grids over the offshore waters for today into tonight as the wind grids have changed little during the next 24 hours or so. Sea heights currently, as of 07z or 0200am EST, range from near 14 to 15 feet off the Jersey Shore to 5 feet over the northern Gulf of Maine per the latest observations. These heights match the ongoing grids and forecast quite well. To match the wind forecast we will rely on the 00z wavewatch for Mon through Tue over the waters with a few manual edits in deference to nearby coastal and TAFB grids. For Tue night into Wed night, we will use a 80 percent wam and 20 percent wavewatch blend and cap sea heights at 13 feet over the eastern nt2 waters near the marginal gale force wind areas for now, where winds are capped at 35 kt. Further adjustments during this time frame are likely over the next few days. For Thu and Thu night, we will return to the previous grids or closer to the 12z wam from yesterday to match the wind forecast.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... .anz800...Gulf of Maine... gale today into Monday night. .Anz805...Georges Bank west of 68w... gale today into Monday night. .Anz900...Georges Bank east of 68w... gale today into Monday night. .Anz810...South of New England... gale today. Gale Monday. .Anz815...South of Long Island... gale today into tonight.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale today. .Anz915...Hudson Canyon to the great South Channel... gale today into Monday. .Anz920...Baltimore Canyon to the great South Channel... gale today. Storm today. Gale possible Wednesday. .Anz905...The great South Channel to the Hague line... storm today. Gale tonight into Monday night. .Anz910...East of the great South Channel and south of 39n... gale today. Storm today. Gale Monday. Gale possible Wednesday. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale today. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale today. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale today. Gale possible Wednesday. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale today. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale today. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale today. Gale possible Tuesday night into Wednesday. .Anz835...Inner waters from Cape Fear to 31n... gale today. .Anz935...Outer waters from Cape Fear to 31n... gale today. Gale possible Tuesday night.
.Forecaster Mills. Ocean prediction center.