marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 250 am EDT Sat Oct 25 2014
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Over the short term...an earlier 0052z ascat-b pass confirmed that Max winds in the nwly gradient acrs the ern nt1 and NE most nt2 wtrs were up to 25-30 kt as prevly expected. The new 00z mdls remain in good agrmt that this gradient wl cont to weaken with dmshng conds into this afternoon. Then the 00z mdls remain consistent and in overall good agrmt timing-wise that conds wl begin to incrs again later today as the next cold front aprchs FM the NW...pushes se ofshr into the nt1 and NW nt2 wtrs tonite...then passes se of the ofshr wtrs by late sun. The mdls all cont to fcst a mod strong wnwly gradient to dvlp bhnd this front with the 00z GFS contg to fcst the strongest gradient. The biggest fcst problem is whether this gradient wl strengthen to gale force or not. Smlr to its prev respective runs...as the attendant sfc low is fcst to strengthen NE of the area and mod negative static stabilities dvlp bhnd the front the 00z GFS conts to fcst gale force 30m bl winds to dvlp in this gradient for a brief period early sun nite...but now over a smwht larger area acrs the srn nt1 and NE nt2 wtrs. With the 00z gefs mean indicating that the 00z GFS may not be strengthening the attendant sfc low fast enuf and with the usually mr conservative 00z UKMET now fcstg a smwht stronger gradient (with solid 25-30 kt bl winds) than its prev 12z run over these same wtrs...hv a slightly higher level of fcst confidence (tho overall stil low) that gales wl dvlp. Therefore plan on populating our short term wind grids with the 00z GFS 10m bl winds for today...then wl transition to its 30m bl winds for tonite thru sun nite. So as a result the most sig short term chngs wl be to make sm areal coverage chngs to the prevly fcstd psbl gales for sun nite.
In the long range...the 00z mdls are in rsnbly good agrmt that as a high pres ridge blds to the coast late Mon/Mon nite that dmnshg conds wl dvlp thrut the cstl/ofshr wtrs...flwd by lite conds contg Tue into Tue nite as the ridge crosses E acrs the wtrs. Then Wed/Wed nite...the 00z GFS/UKMET share smlr timing for the next weaker cold front to push se ofshr acrs the nt1 and nrn/cntrl nt2 wtrs which is about 3-6 hrs on average faster than the 00z Gem/ECMWF fropa. Therefore blv a compromise 00z GFS/ECMWF fropa timing looks rsnbl for now. In regards to the ascd fcst gradients with this fropa...blv a compromise 00z GFS 10m and 00z ECMWF bl solution looks rsnbl. Therefore in the long range wl cont to populate with the 00z GFS 30m bl winds on Mon/Mon nite...then wl transition to its 10m bl winds for Tue/Tue nite. Then Wed/Wed nite wl use a 50/50 blend of the 00z GFS 10m bl winds (time shifted 3hrs slower) and the 00z ECMWF bl winds. So as a result anticipate making only minor long range chngs in the next ofshr fcst package.
Seas...since the differences btwn the two mdls are not sig plan on using a 50/50 blend of the 00z wavewatch iii and 00z ECMWF wam thru Wed nite...except wl go all 00z wavewatch iii for sun thru Mon nite to get slightly higher seas than fcst by the 00z ECMWF wam.
.Extratropical storm surge guidance...Smlr to its prev respective runs...vs the 00z etss the 00z estofs conts to fcst a slightly mr sig negative surge to dvlp along the nrn mid Atlc then new engld coasts in the postfrontal gradient tonite into Mon which per the 00z GFS does not look unreasonable.
.Nt1 New England waters... .anz805...Georges Bank west of 68w... gale Sun night. .Anz810...South of New England... gale Sun night. .Anz815...South of Long Island... gale Sun night.
.Nt2 mid Atlc waters... .anz915...Hudson Canyon to the great South Channel... gale Sun night. .Anz905...The great South Channel to the Hague line... gale Sun night. .Anz910...East of the great South Channel and south of 39n... gale Sun night.
.Forecaster vukits. Ocean prediction center.