marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 831 am EST Sat Dec 3 2016
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Last evenings ascat overpasses did not yet show any gale force winds across the New England and northern mid Atlantic waters. However higher resolution models including the hrrr and 4km NAM both indicate winds have increased somewhat since then and initialize marginal northwest gales across the warmer northern outer nt2 waters this morning. Made some slight adjustments to the wind grids tonight to extend the gales through 09z/04 over these outer waters based on the 00z ECMWF. Otherwise over the short term the previous grids look on target. By early next week the 00z ECMWF continued to offer a compromised timing between the more progressive UKMET and slower GFS with the developing surface low forecast to move off the North Carolina coast early Monday. Later in the week, when compared to its previous run, the 06z GFS trended further north with the track of the next developing low, and offers more differences from the preferred ECMWF/UKMET. With this mornings updates will not be making any changes to the grids at days 3-6.
The previously favored wave height blend of the 00z ECMWF wam and 00z wavewatch iii is in good agreement with this mornings west atlanctic ship and buoy observations. Will not be making any significant adjustments to the previous wave height grids.
----------------------------------------------------------------- Previous discussion...
Over the short term...the new 00z models remain remarkably consistent and in good agreement that as a series of surface trofs sweep offshore a strong WNW gradient with gale force associated boundary layer winds will persist across the nt1 and nrn/central nt2 waters today into tonight. Then Sunday into Sunday night the 00z models all forecast a high pressure ridge to build offshore causing the WNW gradient to gradually weaken with its associated winds diminishing from W to E. Therefore with the models remaining consistent...see no reason to repopulate the previous official wind grids for today into Sunday night...which were primarily the 12z GFS first sigma level winds. So will just make some additional minor edits to these wind grids mainly in deference to the 00z GFS/ECMWF which will not result in any significant changes to the previously forecasted gale warnings for today into tonight.
In the long range...late Sunday night into Monday night...versus its previous 18z run...the 00z GFS remains consistent in forecasting a frontal low to develop off the se coast and then track ewd across the S central nt2 waters...which is supported best by the 00z ECMWF. In general the 00z Gem supports this GFS solution...but the 00z UKMET is more progressive. Therefore...for now as a compromise will populate our forecast winds using our smart tool that will place stronger 00z GFS first sigma winds in unstable areas and weaker 00z GFS 10m boundary layer winds in stable areas and then will blend these winds 50/50 with the 00z ECMWF boundary layer winds for Monday/Monday night.
Then with some timing differences...the 00z global models agree that a stronger surface low will develop and track NE up the se coast Tuesday...then continue NE to near Hatteras Canyon Tuesday night. Overall the similar 00z GFS/UKMET/ECMWF solutions...which are supported by the 00z gefs mean...look more representative for this system than the slower 00z Gem solution. Therefore will continue to populate with a 50/50 blend of the 00z ECMWF boundary layer winds and the 00z GFS first sigma and 10m boundary layer winds for Tuesday/Tuesday night.
Then Wednesday/Wednesday night...the disparity increases between the 00z global models. Versus its previous runs...the 00z GFS now forecasts its surface low to track further N. The 00z gefs mean indicates that the 00z GFS track may be too far N. The 00z Gem track looks like a northern outlier. Therefore would favor the more consistent and more suppressed 00z UKMET/ECMWF solution on Wednesday/Wednesday night. Therefore will transition to populating with the 00z ECMWF boundary layer winds for Wednesday/Wednesday night.
Seas...since the short term winds will not be repopulated...and since the 00z wavewatch iii and 00z ECMWF wam models remain consistent...will continue to the use the previous official forecast wave grids...which were a 50/50 blend of the 12z wavewatch iii and 12z ECMWF wam...for today through Sunday night. Then since a compromise 00z GFS/ECMWF solution will be favored...will transition to populating with a 50/50 blend of the 00z wavewatch iii and 00z ECMWF wam for Monday through Tuesday night. Then since the 00z ECMWF solution will become favored...will switch to populating with all 00z ECMWF wam forecast seas for Wednesday/Wednesday night.
.Extratropical storm surge guidance...In the current strong WNW gradient...similar to its previous respective runs...the 00z estofs continues to forecast a more significant negative surge along the coast from Delaware Bay to Long Island Sound today into tonight than forecast by the 00z etss model. Would again recommend a compromise between the two models for this surge.
.Nt1 New England waters... .anz810...south of New England... gale today. .Anz815...South of Long Island... gale today.
.Nt2 mid-Atlantic waters... .anz915...Hudson Canyon to the great South Channel... gale today into tonight. .Anz920...Baltimore Canyon to the great South Channel... gale today into tonight. .Anz905...The great South Channel to the Hague line... gale today into tonight. .Anz910...East of the great South Channel and south of 39n... gale today into tonight. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale today into tonight. Gale possible Tuesday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Tuesday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Tuesday. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale possible Tuesday into Tuesday night. .Anz835...Inner waters from Cape Fear to 31n... gale possible Tuesday. .Anz935...Outer waters from Cape Fear to 31n... gale possible Tuesday into Tuesday night.
.Forecaster Clark/vukits. Ocean prediction center.