marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 325 am EST Sat 23 Feb 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
The 02z and 0203z ascat overpasses confirmed 25 to 30 kt winds west of the Gulf Stream from near Cape Hatteras extending southwest offshore just south of Cape Fear. The 00z models were generally initialized too low with these winds. Through today, we populated the wind grids with the 00z hiresw/arw and then made adjustments to increase them across the southern nt2 waters north of the statationary front and surface low. So will carry some winds to 30 kt over these areas into the early afternoon. As the coastal front migrates northward today and the surface low southeast of Cape Fear along the warm front weakens, these east to northeast winds should diminish somewhat today and tonight. Will still likely be some winds north of the warm front to 25 kt today and then increasing to 30 kt across the central nt2 waters after midnight tonight.
The 00z models remained quite consistent with the developing coastal surface low and strong cold front expected to impact the nt2/nt1 offshore waters this weekend and early next week. The models also share a similar timing with the front and widespread gales developing ahead of the cold front sun, and winds further increasing (likely to storm force across Georges Bank and the outer northern nt2 zones Mon into Mon night) in the cold air advection in the wake of the cold front Sun night and Mon. We used a blend of the 00z ECMWF and 00z GFS for the wind grids Sat night through Wed. However, to account for the cold air advection Sun night through Tue night, we used a boosted version of the ECMWF winds in the blend during that time. Overall there was not much change to the previous gale and storm warnings. The GFS and ECMWF continued to indicate 925mb winds in the 55 to 65 kt range behind the cold front Sun night and Mon, which given the steep low level lapse rates, even over the colder waters north of the Gulf Stream, should be sufficient to get some storm force winds mixing to the surface. The 00z GFS/fv3-GFS have shown excellent run to run continuity and remained somewhat stronger than the ECMWF and UKMET with these westerly winds. However, when the low bias of the ECMWF and UKMET is taken into consideration in these codl air advection cases, they too support the storm warnings. Given the model consistency, we continue to have well above average confidence with the gale and storm hazards forecast across the offshore waters sun through Tue night.
Model differences then increase greatly across the west Atlantic by the middle of the week. The GFS/fv3-GFS/UKMET are much stronger with the south to southwest gradients across the offshore waters late Wed and Wed night ahead of a developing surface low and cold front, while the ECMWF has consistently offered a more suppressed surface low off the southeast coast. Given the forecast uncertainty which arises, we are choosing to use a blend of the GFS/ECMWF with more weight given to the weaker ECMWF at this time. This will result in a wind field which is generally in line with the latest wpc medium range guidance Wed/Thu which is much weaker than the GFS/fv3-GFS/UKMET solutions.
.Seas: the higher ECMWF wam is better initialized than the wavewatch off the North Carolina coast this morning. Also, during the gale/storm force winds, the wam is also higher, generally 10 to 15 percent, than the ww3. We will be populating the wave height grids with a 75/25 wam/ww3 blend. We did then adjust the near term wave heights higher by about 15 percent or so off the coast of the Carolinas to better match the buoy observations.
.Extratropical storm surge guidance...The 00z estofs shows surge values around 1 to 1.5 ft over the southern and northern New England coasts sun into Sun night as the onshore flow north of the warm front increases. The 00z etss is well below 1 ft, except near the eastern coast of Maine and Bay of Fundy where it shows surge up to 1.5 to 2 ft sun evening. The etss appears too low at least across Long Island Sound. The models do indicate any surge should be relatively short lived which seems reasonable given the rapid northward movement of the warm front. For more details please monitor the latest forecast and information from your local National Weather Service office.
.Nt1 New England waters... .anz800...Gulf of Maine... gale Sunday into Sunday night. Gale possible Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday. .Anz805...Georges Bank west of 68w... gale Sunday into Sunday night. Storm possible Monday into Monday night. Gale possible Tuesday into Wednesday. .Anz900...Georges Bank east of 68w... gale Sunday night. Storm possible Monday into Monday night. Gale possible Tuesday into Wednesday. .Anz810...South of New England... gale Sunday into Sunday night. Storm possible Monday. Gale possible Monday night into Tuesday. .Anz815...South of Long Island... gale Sunday night. Gale possible Monday into Monday night.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale Sunday night. Gale possible Monday into Monday night. .Anz915...Hudson Canyon to the great South Channel... gale Sunday into Sunday night. Storm possible Monday. Gale possible Monday night into Tuesday. .Anz920...Baltimore Canyon to the great South Channel... gale Sunday into Sunday night. Gale possible Monday into Tuesday. .Anz905...The great South Channel to the Hague line... gale Sunday into Sunday night. Storm possible Monday into Monday night. Gale possible Tuesday into Wednesday. .Anz910...East of the great South Channel and south of 39n... gale Sunday into Sunday night. Storm possible Monday into Monday night. Gale possible Tuesday into Wednesday. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale Sunday into Sunday night. Gale possible Monday. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale Sunday into Sunday night. Gale possible Monday. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale Sunday into Sunday night. Gale possible Monday into Monday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale Sunday into Sunday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale Sunday into Sunday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale Sunday into Sunday night. .Anz835...Inner waters from Cape Fear to 31n... gale Sunday into Sunday night. .Anz935...Outer waters from Cape Fear to 31n... gale Sunday into Sunday night.
.Forecaster Clark. Ocean prediction center.