marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 357 PM EST Mon Jan 21 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Per the 18z NCEP surface analysis a trough of low pressure, associated with a strong 987 mb low over the Gulf of Saint Lawrence, was draped across the Gulf of main over the far N nt1 waters. A broad high pressure, centered over the Great Lakes, extended its ridge into the nt2 waters. The latest available ascat high resolution data revealed 25-35 kt winds over the nt1 waters, except over the Gulf of main where 20-25 kt winds were noted. A large area of 25-35 kt was noted over the outer nt2 waters, with 20-30 kt winds over the SW nt2 waters.
For the most part the latest 12z guidance had fairly good agreement through Fri 18z. Feel it's reasonable in the near term to allow the ongoing wind grids to remain in place through Wed 03z. Per observations from ascat, ongoing gales are confirmed over the opc offshore waters. As the parent low, over the Gulf of Saint Lawrence, continues moving NE, strong cold air advection overspreading the region will allow for continued gales through late Tue night. Concerning storm force winds over parts of the outer nt2 waters, the 12z GFS/ECMWF/UKMET continue to show 40 kt surface winds along the north wall of the Gulf Stream. Adding in model consistency and taking into account the fact that this is some of the coldest air aloft of the year moving offshore, continue to feel the chance for periods of storm force conditions in the aforementioned waters remain valid. Some small edits to slightly increase the spatial coverage of the storm force winds were made, but nothing that will result in significant changes to the ongoing storm warnings. Still unstopped winds finally subsiding below warning criteria late Tue night as high pressure moves E off the eastern U.S. Seaboard and across the waters.
Next system approaches the eastern Seaboard Thu, with low pressure moving NE through New England while pulling its strong front E through the waters later Thu through Fri. Here the 12z GFS is slightly faster than the 12z ECMWF/UKMET/CMC concerning passage of the front initially, though by Fri once the front has cleared the waters, the location of the front among the guidance comes into better agreement. Despite the slight timing differences, the idea of widespread southerly gales over the opc offshore waters ahead of the front is apparent in all the guidance. Additionally both the 12z GFS/ECMWF continue to suggest the chance for pockets of southerly storm force winds in the outer nt2 waters in the vicinity of the Gulf Stream late Thu night. This was also present in the ongoing forecast as well. With that noted, feel using the 12z ECMWF from about Wed 06z through Fri 18z is a good compromise here. This will result in warning hazards generally remaining the same early Thu into Fri.
By Sat day 5, guidance remains divergent in regards to the next system impacting the waters. Guidance suggest the potential for low pressure to move through the waters, or just to the se, but the spread in the guidance concerning the strength and track is noticeable. The 12z GFS moves a weak low along the NC coast before absorbing it into a cold front moving offshore late Sat, the 12z ECMWF has low pressure moving off of se VA/NE NC and into the northern nt1 waters by late Sat, the 12z UKMET develops a gale low E of the southern nt2 waters Sat and moves it NE, while the 12z CMC develops a low just E of the FL/GA border. So with the amount of uncertainty seen on day 5, feel it makes sense to go with a persistence forecast here, maintaining the existing grids in place.
.Seas...Through Wed 03z will allow the ongoing grids to remain in place given only minor adjustments will be made to the grids, mainly increasing the spatial area of the storm force winds in the outer nt2 waters a bit overnight into Tue. Afterwards, preference is to favor the 12z ECMWF wam through Fri 18z given the choice to use the 12z ECMWF winds. With the strong southerly flow anticipated ahead of the cold front Thu into Fri, the latest wam model increases seas a bit higher than what the previous guidance had, actually suggesting a brief period of 30 ft seas overnight Thu into Fri in the vicinity of the Gulf Stream. However, for now feel that may be a bit to high, hence will cap seas at 28 ft during the Thu night into early Fri time frame, which is still a bit higher than the previous forecast which had 26 ft for the same time frame and locations. For the remainder of the period after Fri 18z, will transition back to the ongoing grids given the choice to continue with a persistence forecast given the aforementioned differences seen in the global guidance.
.Extratropical storm surge guidance...No significant positive surge events are likely into Tue over the region with offshore winds prevailing over most areas and a negative surge forecast for most areas into Tue. The next potential for a positive surge event will be Wed into Thu as the next low pressure system approaches the region from the W, and strong southerly winds develop over the waters. Please monitor the latest more detailed information from the coastal National Weather Service forecast offices over the next few days.
.Nt1 New England waters... .anz800...Gulf of Maine... gale tonight into Tuesday. Heavy freezing spray tonight into Tuesday. Gale possible Thursday into Thursday night. .Anz805...Georges Bank west of 68w... gale today into Tuesday. Heavy freezing spray tonight into Tuesday. Gale possible Thursday into Thursday night. .Anz900...Georges Bank east of 68w... gale today into Tuesday. Gale possible Thursday into Thursday night. .Anz810...South of New England... gale today into Tuesday. Heavy freezing spray tonight. Gale possible Thursday into Thursday night. .Anz815...South of Long Island... gale today into Tuesday. Gale possible Thursday.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale today into tonight. Gale possible Thursday. .Anz915...Hudson Canyon to the great South Channel... gale today into Tuesday. Gale possible Thursday. Storm possible Thursday night. .Anz920...Baltimore Canyon to the great South Channel... storm today into tonight. Gale Tuesday. Gale possible Wednesday night into Thursday. Storm possible Thursday night. .Anz905...The great South Channel to the Hague line... gale today into Tuesday night. Gale possible Thursday. Storm possible Thursday night. .Anz910...East of the great South Channel and south of 39n... storm today into tonight. Gale Tuesday. Gale possible Thursday. Storm possible Thursday night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale today into tonight. Gale possible Thursday. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale today into tonight. Gale possible Wednesday night into Thursday. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale today into Tuesday. Gale possible Wednesday night into Thursday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale today into tonight. Gale possible Wednesday night into Thursday. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Wednesday night into Thursday. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale today into tonight. Gale possible Thursday into Thursday night. .Anz835...Inner waters from Cape Fear to 31n... gale possible Wednesday night into Thursday. .Anz935...Outer waters from Cape Fear to 31n... gale possible Wednesday night into Thursday night.
.Forecaster Holley. Ocean prediction center.