marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 259 PM EDT sun Apr 19 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Over the short term...the new 12z mdls remain consistent in fcstg a warm front to mov NE off the mid Atlc coast late tonite...then cont NE up the coast thru Tue with a strong (gale force) esely gradient dvlpg to its immed N and NE. In rgrds to the fcst timing of this warm fropa the differences btwn the 12z mdls are negligible. In rgrds to its ascd fcst gradients blv the very consistent 12z GFS solution looks lk a rsnbl compromise btwn the slightly stronger 12z NAM/Gem and slightly weaker 12z UKMET/ECMWF solutions. Therefore smlr to the prev ofshr fcsts wl populate our fcst wind grids with the slightly mr conservative 12z GFS 10m bl winds (to better account for the warm air advection in this gradient acrs the colder nrn wtrs that wl limit the low level mixing) for tonite into Tue which wl result in only very minor chngs to the prevly fcstd gale wrngs and ascd fcst conds. Then again as was done prevly...to better account for the cold air advection ascd with the weak cold front fcst to sweep ofshr late Mon nite/Tue wl transition to populating with the 12z GFS 30m bl winds later Tue/Tue nite. So overall anticipate making no sig short term chngs in the next ofshr fcst package.
In the long range...the new 12z global mdls gnrly agree that a closed upr low wl translate ever so slowly E acrs srn Quebec by Wed nite into Fri nite with a series of S/W trof rotating around it. At the sfc...tho they hv timing differences...the 12z global mdls gnrly agree that a cold front wl move ofshr into the nrn wtrs Wed nite...then push se acrs the ofshr wtrs Thu into Fri. By late Thu into Fri nite the disparity btwn the 12z global mdls increases in rgrds to frontal waves dvlpg and intensfyg E of the ofshr wtrs. The 12z ECMWF fcsts the most amplified solution with an intense sfc low dvlpg E of Georges Bank Fri nite. The 12z UKMET flws the trends of the 12z ECMWF but is weaker. The 12z GFS tho fcsts a less amplified ptrn that is sprtd by the 12z Gem/gefs and is mr in line with the latest wpc medium range guidance. Therefore with low fcst confidence...wl populate our fcst wind grids with the 12z GFS 10m bl winds Wed into early Thu...then wl transition to the 12z GFS 30m bl winds later Thu into Fri nite. So due to the large disparity btwn the mdls wl hold off on fcstg any ascd psbl gale wrngs in the long range.
.Seas...With the differences btwn the two mdls rmng minimal...smlr to the prev ofshr fcst package...wl use a 2 to 1 blend of the 12z wavewatch iii/12z ECMWF wam for tonite thru Tue nite. Then wl populate with all 12z wavewatch iii from Wed thru Fri nite with low fcst confidence.
.Extratropical storm surge guidance...As the sely gradient is fcst to strengthen tonite sun and then shift newd up the coast into Tue nite...the 12z estofs conts its prev trends of fcstg a slightly mr sig positive surge spread nwd up the coast than fcst by the 12z etss. Blv a compromise btwn the two mdls wl lkly verify best for this surge.
.Nt1 New England waters... .anz800...Gulf of Maine... gale Mon night into Tue. .Anz805...Georges Bank west of 68w... gale Mon night. .Anz900...Georges Bank east of 68w... gale Mon night into Tue. .Anz810...South of New England... gale Mon into Mon night. .Anz815...South of Long Island... gale Mon into Mon night.
.Nt2 mid Atlc waters... .anz820...Hudson Canyon to Baltimore Canyon... gale Mon. .Anz915...Hudson Canyon to the great South Channel... gale Mon into Mon night. .Anz920...Baltimore Canyon to the great South Channel... gale Mon into Mon night. .Anz905...The great South Channel to the Hague line... gale Mon into Tue. .Anz910...East of the great South Channel and south of 39n... gale Mon into Mon night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale tonight into Mon. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale tonight into Mon.
.Forecaster vukits. Ocean prediction center.