marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 430 PM EDT Tue 19 Mar 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
The 1420z and 1450z ascat overpasses returned an expansive area of north to northeast winds 25 to 30 kt across the offshore waters south of about 36n. Ascat also indicated the coastal front developing over the inner zones from east of Cape Hatteras southward. Based on the 12z high resolution models, we will retain the gale warnings across the inner zones south of Cape Hatteras through 12z Wed. Across the outer nt2 zones south of Hatteras Canyon, the 12z models are consistent that more widespread easterly gales will occur tonight into early Wed afternoon. Through Wed, the updated wind grids are based on a blend of the 12z ECMWF and 12z hiresw/nmm. Once the persistent high pressure ridge across the nt1 and northern nt2 waters shifts east of the offshore waters, low pressure is expected to develop off the southeast coast along the stationary front late Wed and Wed night.
Over the last day or so, the GFS/ECMWF/fv3-GFS have exhibited a notable westward shift with the coastal low track Thu/Thu night, and now are showing a track which hugs the coast. The models have also trended weaker with the associated winds. The 12z gefs and 00z ECMWF ensemble means were slightly east of the aformenetioned deterministic cluster. To incorporate the weaker westward trend, we are opting to update our wind grids for the Wed night through Thu night period with a 2:1 blend of the 12z ECMWF and the previous wind grids. We will be dropping the gale force winds in the southerly flow across the inner nt2 zones as well as over the south of New England zones. Given the continued model discrepancies as well as the lack of much run to run continuity, our confidence with these gale hazards remains slightly below average. Our confidence is then far greater with the northwest gales expected in the wake of the low Fri into the weekend. The 12z models are very consistent that the strong low slowly migrates northeast near the Canadian Maritimes and high presssure builds east toward the New England and mid-Atlantic coasts. By sun and Sun night, winds should finally begin to diminish as high pressure builds across the nt2 waters and the low accelerates further northeast across the North Atlantic. To account for the cold air advection, we used a boosted version of the 12z ECMWF winds blended with the 12z GFS Fri through sun. The west to northwest gale force winds will be quite widespread across the offshore waters north of Hatteras Canyon.
.Seas: we will generally base the near term grids on the latest ECMWF wam guidance, however in strong to gale force winds opposing the Gulf Stream, will continue to make 15-20 percent increases to this model guidance. Later in the week, will use a 2:1 blend of the 12z ECMWF wam and 12z wavewatch.
Extratropical storm surge guidance: the persistent strong to gale force northeast flow across the southern mid Atlc waters through about Wed is expected to support surge values around 1 to 1.5 ft, perhaps up to 2 ft from Cape Lookout to the Georgia coast Wed into Wed night. This is consistent with the 12z estofs which is much higher than the 12z etss. The with the developing coastal low causing onshore flow up the coast, there is potential for minor to moderate surge from the New Jersey coast along the New England coast including Long Island Sound late Thu into early Fri. Again the higher 12z etofs appears more representative. With the GFS winds appearing somewhat weaker than some other models, even these estofs surge values may be too low. Consult your local National Weather Service office for more detailed information.
.nt1 New England waters... .Anz800...Gulf of Maine... gale possible Friday. Gale possible Saturday. .Anz805...Georges Bank west of 68w... gale possible Friday into Saturday. .Anz900...Georges Bank east of 68w... gale possible Thursday night into Saturday night. .Anz810...South of New England... gale possible Friday into Saturday night. .Anz815...South of Long Island... gale possible Friday into Saturday night.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale possible Friday into Saturday night. .Anz915...Hudson Canyon to the great South Channel... gale possible Friday into Saturday night. .Anz920...Baltimore Canyon to the great South Channel... gale possible Thursday night into Saturday night. .Anz905...The great South Channel to the Hague line... gale possible Thursday night into Saturday night. .Anz910...East of the great South Channel and south of 39n... gale possible Thursday night into Saturday night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale possible Friday night into Saturday. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale possible Friday night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale Thursday. Gale possible Thursday night into Saturday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Friday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale today into Wednesday. Gale possible Friday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale tonight into Wednesday. Gale possible Friday night. .Anz835...Inner waters from Cape Fear to 31n... gale today into Wednesday. .Anz935...Outer waters from Cape Fear to 31n... gale tonight into Wednesday.
.Forecaster Clark. Ocean prediction center.