marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 259 PM EDT sun Apr 30 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, the new 12z models overall remain consistent and in very good agreement in regards to the expected synoptic pattern. The models share similar forecast timing for a stationary front now across the nrn nt2 waters to return nwd across the waters as a warm front later tonight into Mon night with a gradually strengthening sly gradient developing throughout the waters. Then late Mon night into Tue as a cold front is forecast to push offshore the 12z GFS remains very consistent versus its previous respective runs in forecasting the sly gradient to strengthen to gale force across the nt2 waters S of the Gulf Stream. With the 12z GFS forecasting an associated 45-60 kt sly low level 925 mb jet to develop over the nt2 waters in association with this cold fropa and the usually conservative 12z UKMET/ECMWF now also forecasting gale force sly prefrontal boundary layer (bl) winds, forecast confidence is now high that these gales will develop. Therefore as has been done for the past several forecast packages, plan on populating our forecast wind grids with the respresentative 12z GFS solution for tonight through Tue night using our smart tool that will place stronger 12z GFS first sigma level winds in unstable areas and weaker 12z GFS 10m winds in stable areas (which will be over the majority of the waters). So per these winds do not anticipate making any significant timing and/or areal coverage changes to the previously forecasted gale warnings on Mon night/Tue.
In the long range, by late Tue/Tue night the 12z models agree that the cold front will wash out and be followed by a secondary cold front sweeping offshore Tue night/Wed, then stalling across the S central nt2 waters Wed night with moderately strong (generally up to 20-25 kt) associated gradients. So will continue to populate with the representative 12z GFS first sigma and 10m winds on Wed/Wed night with some minor additional edits in deference to the 12z ECMWF.
Then further out in the long range, though they differ in regards to their forecast tracks of the associated attendant surface low tracking slowly NE from the se conus Thu/Thu night towards New York state by late Fri/Fri night, the 12z global models in general agree that the stalled front will slowly lift back nwd across the waters as a warm front Thu into Fri night, followed by a cold front pushing offshore late Fri/Fri night. The primary result of this pattern will be a strengthening sly gradient developing late Thu across the srn nt2 waters and then spreading nwd Thu night into Fri night, with gale force winds likely developing again across the nt2 waters primarily from the Gulf Stream swd. Overall will favor the 12z GFS solution for these fropas since its supported by the 12z Gem/UKMET/gefs mean and is only slightly less progressive than the 12z ECMWF. Therefore will continue to populate 12z GFS first sigma and 10m winds on Thu through Fri night.
Seas...the 12z wavewatch iii and 12z ECMWF wam models have both initialized the current seas throughout equally well. With this in mind and since their associated 12z GFS and 12z ECMWF solutions are similar and their forecast differences generally remain in the 1-2 ft range, will populate our forecast wave grids with a 50/50 blend of the 12z wavewatch iii and 12z ECMWF wam for tonight through Wed night. Then Thu and beyond since the 12z GFS solution will become preferred, will transition to populating with all 12z wavewatch iii seas then.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid-Atlantic waters... .anz920...Baltimore Canyon to the great South Channel... gale Monday night into Tuesday. Gale possible Tuesday night. Gale possible Friday night. .Anz910...East of the great South Channel and south of 39n... gale Tuesday. Gale possible Tuesday night. Gale possible Friday night. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale Monday night into Tuesday. Gale possible Friday into Friday night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale Monday night into Tuesday. Gale possible Friday into Friday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale Monday night into Tuesday. Gale possible Friday into Friday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale Monday night into Tuesday. Gale possible Friday into Friday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale Tuesday. Gale possible Friday into Friday night. .Anz835...Inner waters from Cape Fear to 31n... gale possible Thursday night into Friday. .Anz935...Outer waters from Cape Fear to 31n... gale possible Friday night.
.Forecaster vukits. Ocean prediction center.