marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 953 am EDT Wed Apr 1 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
The Sat img has most of the conv clds ovr the ern wtrs where there is strng ind of dense lightng strikes. Radar shows no tstms cells ovr the wtrs mainly because its coverage does not extnd to the ern wtrs. Sref indct that there is up to 25 percent chance of sev tsms ovr the ern parts of the region today. At 1200z low pres 999 mb ovr the far N-ern balt cnyn has a cld frnt that stretches SW to pass just E of the cntrl region and then acrs the srn wtrs. Inland hgh pres has wk ridge just behind the frnt ovr the srn wtrs. The pres grdnt is fairly tight ovr the N-ern wtrs where there are Max winds reaching gale force. The hgst seas are also ovr the N-ern parts with 13 ft peaks. Seas subside to 4 ft ovr the S-wrn wtrs and the N-wrn wtrs.
The mdls hv initialized well and they contne to be in gud agrmnt and so will will upadte the fcst with mnr chnges from the previous fcst and will retain most of the wrngs follwing GFS. In the short term low pres will zoom NE while a hgh pres moves into the srn wtrs. The pres grdnt will relax and allow winds to diminsh to below gale force.
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Crnt NCEP final anal for 06z has clipper-type low S of Nantucket nr 39n with a trailing fntl bndry extending SW to nr hat cnyn and ascat image FM 0210z shows SW winds at or nr gale force at pass edge FM zone 920 swd mainly alg and S of glf stream. Current ltgng data indc strikes alng the bndry...mainly ovr warmer wtrs S of 38n...and ovr outer ofshr wtrs where fnt is most active. With the rapid movmt of system gales are lkly sprdg rpdly ENE so current fcst apprs on target. 00z GFS apprs well initialized with low which wl pass E and NE of nernmost nt2 zone Wed mrng and ascd GFS bl wnds are slgtly higher than other mdls but have been consistent. Favor 00z GFS 30m wnds both with low and the incrg caa bhnd the low thru Wed night.
Otrw...the 00z mdls are in gud agrmt thru Sat night with the prgrsv pttn...indcg a rdg wl build in behind the front today thru Thu. The 00z mdls then indc anthr pair of shrtwvs wl cross the W Atlc Fri and Sat...and the 00z GFS after trending twd more consistent ECMWF 6 hrs earlier has gone back to a more srn track thru srn New England of the stronger of a pair of low pres waves. Then 00z mdls indc a frtnl bndry wl stall ovr nrn nt1 Fri...before the second shrtwv and low moves off the nrn mid Atlc coast Fri ngt into Sat. The assoc frntl bndry is xpctd to mov E off the coast...as the sfc low passes just N of nt1 Sat. The GFS is also a bit faster than other mdls with stronger low and remains stronger with sfc wnds than the ecwmf...and indc storm frc winds ahd of the sfc frnt in srly flow. The GFS seems overdone...so confdc with the storm frc is low attm. However...confdc is abt MDT to hi in the gales...as most solns indc at least that intnsty. Attm planning on shftg FM 00z GFS to 00z ECMWF after 06z Fri sprtd by 00z Gem/UKMET.
The 00z mdls also indc anthr shrtwv wl cross nt1 with a cdfnt at the sfc sun. The GFS is again stgr with the wnds...versus other mdls...and confdc with gales is low...and system passes thru vry quickly. Again favoring 00z ECMWF which is consistent into sun and then late sun and Sun night prefer old 12z ECMWF which is more lk UKMET/Gem stalling a fnt S of New England but does not dvlp a strong low ovr New England Sun night that newer run is doing.
Seas...the 00z mww3 and ECMWF are init within a ft of the crnt data ovr most of the W Atlc. The 00z mdls seem rsnbl...and only differ with the aforementioned diff in wx mdl intnsty. As a result...planning on using a 50/50 blend of wave hgts initially thru Thu night where GFS sfc fcst is preferred...then shift to 00z ECMWF wave mdl excp after sun the older 12z/31 ECMWF wam.
.Extratropical storm surge guidance...00z guid indc a slgt neg surge with stg NW ofshr flow behind series of fast movg fnts thrut the pd. Largest neg surge 1 to 2 ft dvlps mid Atlc CST with the strong fnt movg thru the watlc Sat into sun...and neg surge looks a ltl high in that time frame.
.Nt1 New England waters... .anz800...Gulf of Maine... gale possible Sat into Sun night. .Anz805...Georges Bank west of 68w... gale possible Fri night into Sat. Gale possible sun. .Anz900...Georges Bank east of 68w... gale possible Fri into Sat. Gale possible sun into Sun night. .Anz810...South of New England... gale possible Fri night into Sat. Gale possible sun. .Anz815...South of Long Island... gale possible Fri into Sat. Gale possible sun.
.Nt2 mid Atlc waters... .anz820...Hudson Canyon to Baltimore Canyon... gale Thu night. Gale possible Fri into Sat. .Anz915...Hudson Canyon to the great South Channel... gale possible Fri into Sat. Gale possible sun. .Anz920...Baltimore Canyon to the great South Channel... gale possible Fri into Sat. Gale possible sun. .Anz905...The great South Channel to the Hague line... gale Thu night. Gale possible Fri into Fri night. Storm possible Sat. Gale possible sun into Sun night. .Anz910...East of the great South Channel and south of 39n... gale possible Fri into Fri night. Storm possible Sat. Gale possible sun into Sun night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale possible Fri into Sat. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale possible Fri into Sat. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale Thu night. Gale possible Fri into Sat. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Fri night into Sat. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Fri night into Sat. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale possible Fri night into Sat.
.Forecaster musonda/Bancroft. Ocean prediction center.