marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 244 PM EST Mon Dec 18 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Current conditions...the 12z NCEP surface analysis shows a weak 1017 mb low centered in the waters near the New Jersey coast, with an associated front extending se from the low and across the northern nt2 waters, with a cold front extending SW over the central and southern nt2 waters. Otherwise, the analysis shows high pres ridging over the offshore waters. Latest available ascat and ascat hi-res passes from last night indicate 20 to 25 kt winds over the outer of the northern and central nt2 waters, and 10 to 20 kt winds across much of the remaining offshore waters. The weak low will pass E over the northern nt2 waters later today, then move off to the E and strengthen tonight. A strong cold front will pass se over the offshore waters Tue night and Wed, then stall across the southern nt2 waters late Wed and Wed night, so we continue to have gale warnings up that timeframe for the nt1 and NE nt2 waters with average confidence. Another low will pass E across the southern nt2 waters Wed night into Thu while pulling a second cold front over the area. A large high pres ridge will work its way E across the offshore waters late Thu through Fri night. Another cold front will approach the New England and New Jersey coasts late Sat, then move offshore Sat night.
Models/forecast...the 12z medium range models are in good overall agreement across the offshore waters during the forecast period, except the 12z GFS looks like a significantly fast and strong outlyer solution for Fri through Sat. The ascat winds have been coming in a bit stronger than what has been suggested by the ECMWF, so will be going with a 50/50 blend of the 12z ECMWF and the more robust 12z GFS 30m solution for tonight through Wed. The more consistent and representative 12z ECMWF will be used exclusively for the wind grids for Wed night through the rest of the forecast period.
Seas...the 12z wna wavewatch and 12z ECMWF wam both initialized well across the offshore waters. The wavewatch and ECMWF wam are in good agreement over the offshore waters for tonight through Wed, with only minor differences noted in a few areas, so will use a 50/50 blend of the 12z wavewatch/wam for the wave height grids during this timeframe to smooth out the model differences. Then will go exclusively with the 12z ECMWF wam for Wed night through the rest of the forecast period, in order to be consistent with the strongly preferred 12z ECMWF wind grids.
Extratropical storm surge guidance...N/A.
.Nt1 New England waters... .anz800...Gulf of Maine... gale Tuesday night into Wednesday. Gale possible Saturday. .Anz805...Georges Bank west of 68w... gale Tuesday night. .Anz900...Georges Bank east of 68w... gale Tuesday night into Wednesday.
.Nt2 mid-Atlantic waters... .anz905...the great South Channel to the Hague line... gale Tuesday night into Wednesday.
.Forecaster Scovil. Ocean prediction center.