marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 817 PM EST Tue Mar 3 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
GOES IR imgry indc a powerful hurricane force low pres system well to the NE of the wtrs...and a dvlpg sys to the W of the wtrs inlnd ovr the grt lks rgn. In btwn the two systems...the GOES WV imgry indc a rdg...crntly acrs the ofshr wts...but movg quickly to the E. The 1905z and 2045z rscat wnd rtrvls indc high pres acrs the NE ptn of the ofshr wtrs...and S to se flow along the coast...ahd of the aprchg frntl sys. The GFS indc the srly winds wl incrs as the frnt moves off the coast...up to gales frc with the stg frntl frcg. The GFS indc nr 45 kt in the NE ofshr wtrs...then storm frc E of the waters Wed. The 30m wnds seem a ltl overdone ovr the cd wtrs N of the glf strm...which shud inhibit the stgr wnds aloft FM mxg dn to the extent shown by the 30m GFS wnds. The prev favored the 30m wnds ovr the less stable wtrs to the S and E of the flg strm...and 10m wnds to the N and W of it. The prev fcst then switched to all 30m wnds as the frnt clears the area...lvg the ofshr zones under the influence of stg caa. Gales seem likely...but storm frc seems to stg. The rest of the mdls agree fairly well with the GFS on the tmg and intsty of this sys...so as a result planning attm on not mkg any sig changes FM the prev fcst.
Also...the mdls indc the tail end of the frnt wl hang up ovr the srn wtrs Thu into Fri...as a high pres rdg extends E to the N of the frntl bndry. This wl lv zones to the N of it in a N to NE flow regime...which looks to be unstable with a stg pres grad. The prev fcst had gales for this pd...which seems rsnbl with the caa ovr the glf strm. Confdc with the gales is low to MDT...so planning on keeping them in the update pkg.
Otrw 12z/18z mdls agree fairly well in the extended pd...and indc a wkr pttn. There are some diffs on the details...esp with low pres that the GFS shows dvlpg ovr the N ptn sun. The rest of the mdls do now indc much of a low...and in fact the ecwmf indc a high pres rdg wl move more slowly than the GFS. The ecwmf has a bit more support FM the rest of the 12z guid...so with theprev fcst favoring it...planning on staying with the ecwmf in the extended.
----------------------------------------------------------------- Previous discussion...
12z global models in good agrmt thru most of the fcst period...with some differences noted in the day 4-5 time frame. Populated wind grids from the 12z GFS thru 00z Sat...then transition to 12z ECMWF thru the remainder of the period.
Latest ascat passes FM 128z and 1428z show gale conditions S of Nova Scotia and arnd island of nfld excp storm NE of nfld while ovr ofshr and cstl wtrs wnds are less then 20 kt in rdg conds excp Ely flow noted S of Hatteras with hint of a wrm fntl bndry and dvlpg cstl trof/fnt focusing stronger wnds arnd 20 kt in hi res ascat-a data. Passes miss outer wtrs.
Models continue to be in good agrmt with timing and strength of next system to affect the region tonight into Wed night. Front approaches coast tonight and moves offshr Wed. Front stalls across cntrl nt2 waters Wed night...with frontal wave(s) moving NE along the front and across the cntrl nt2 waters Wed night into Thu night. Final wave then pushes fnt S thru srn waters Thu and Thu night...with strong high pres building in behind the front. Will continue to populate wind grids with 10m winds for the sly flow ahead of the front...especially in the more stable and cooler SSTs over nt1 waters. For winds behind the front...with more unstable conditions dvlpg in the strong cca behind the front...will populate with the 30m winds in the nly flow behind the front. Main change for gales ahd of fnt is to add gale to NE glf of Maine with more channeling close to Nova Scotia and Bay of Fundy with more enhanced flow ahd of wrmfnt movg into that area late tonight based on the GFS 10m wnds. Otrw no major changes to the gales ahead of the front...with gales expected across srn nt1 as well as nrn and cntrl nt2 waters in the sly flow ahead of the front. For Post frontal gales...will continue with gales for the srn and cntrl nt2 waters Thu into Thu night...extending briefly into nrn nt2 zones S of 38n Thu night.
For Sat and sun...another front expected to move off the coast late in dasy then sweep offshore. Will continue with trend of using more stable 10m winds for the sly flow ahead of the front. GFS/ECMWF/UKMET in fairly good agrmt with the timing and strength of the front. GFS does dvlp low along the remnants of the frontal boundary to push thru area earlier in the week S of the area and moves it into srn waters late in the period. Both the ECMWF and the UKMET keep any low dvlpmt weak and suprressed to the S thru the fcst period...and rdg blds ovr area sun with lgt wnds. Will transition wind grids to 12z ECMWF beginning 00z Sat and continue thru the remainder of the fcst period.
.Seas...Populateed wave grids with 12z ECMWF wam thru 00z Wed then 50/50 blend of the 12z ECMWF wave and 12z wna until 00z Thu as it continues to be a good compromise between the higher values of the ECMWF wave and the lower values of the wna. After 00z Thu and until 00z Sat used 12z wna and after that 12z ECMWF wave and continue thru the remainder of the fcst period...as am leaning towards ECMWF solution for winds during this portion of the fcst.
.Extratropical storm surge guidance...12z estofs showing between a half a ft to a ft surge along the Maine coast tonight in the sly flow ahead of the front excp 1.5 ft in Bay of Fundy...abt hlf ft more than etss..and estofs picks up on dvlpg neg surge mid Atlc CST to srn New England bhnd fnt more than etss later Wed into Wed night.
.Nt1 New England waters... .anz800...Gulf of Maine... gale tonight. .Anz805...Georges Bank west of 68w... gale tonight. .Anz900...Georges Bank east of 68w... gale tonight into Wed.
.Nt2 mid Atlc waters... .anz915...Hudson Canyon to the great South Channel... gale tonight into Wed. .Anz920...Baltimore Canyon to the great South Channel... gale tonight into Wed. Gale possible Thu night. .Anz905...The great South Channel to the Hague line... gale tonight into Wed. .Anz910...East of the great South Channel and south of 39n... gale tonight into Wed. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale possible Thu night. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale tonight into Wed night. Gale possible Thu night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale tonight into Wed night. Gale possible Thu night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Thu night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Thu night into Fri. .Anz835...Inner waters from Cape Fear to 31n... gale possible Thu night into Fri.
.Forecaster Kells/Bancroft. Ocean prediction center.