marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 812 PM EST sun Mar 1 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
No sig changes to the fcst or headlines for this package.
Low pres expected to move NE across nt1/nrn nt2 tonight while intensifying. Gales expected to dvlp in the swly flow ahead of the front over the nrn nt2 waters tonight. Low expected to push strong cold front across the region tonight into Mon...with gales across nt1 and nrn/cntrl nt2 in the strong cca behind the front. Will not make any changes to the timing of the headlines attm.
Seas...wna version of wwiii within a ft or two of current obs.
----------------------------------------------------------------- Previous discussion...
Summary...high pres ovr NE nt2 and se nt1 off wtrs this aftn will slide E away from the region tngt. Eariler ascat and r-scat passes indicated winds at 25 kt or less ovr the off wtrs this morning. Obs from the region still indicate the strongest winds ovr srn nt2 wtrs...up to 25 kt or so. The main wx features that will impact conditions ovr the region during the next several days will cont to be a series of strong cold frontal passages. The first in the series of strong cold fronts will sweep E over the offshore waters tonight into Mon as high pres moves E away from the region. Another strong high pres area will build E toward the waters in the wake of the front later Mon into Tue. The second strong front will approach the waters Tue night into early Wed...movg se ovr the nt1 and nrn nt2 wtrs during Wed...and then slowly movg se ovr central and srn nt2 wtrs Wed ngt into Thu as weak low pres slides E along the front. Strong high pres will once again follow...and build E ovr the wtrs later Thu into Fri ngt.
Models and headlines...for tngt thru Wed the 12z glbl mdls remain in vry good agreement ovr the off wtrs. We will therefore remain close to what was used previously and use the 12z GFS 10m winds ahead of each cold front in the SW flow...and then switch to using the higher 30m winds from the 12z GFS in the stronger cold air advection behind each cold front thru Wed. This will result in little change to the prev fcst and headlines ovr the off wtrs for tngt thru Wed...with confdc lvls abv average. For Wed ngt thru the remainder of the fcst we will trend the off wtrs fcst toward the 12z ECMWF as it appears to depict the passage of the ltr Wed into Thu front a little better than the 12z GFS in that the frontal passage is a tad slower than the 12z GFS which appears to be a slightly faster outlier...and also indicates a wk low movg NE along the front similar to the 12z UKMET mdl guid. We will boost the 12z ECMWF winds in the NW to N wind flow behind the front...espec in and near the Gulf Stream Wed ngt into Thu ngt. This will keep gales going ovr portions of the srn and central nt2 off wtrs Wed ngt into Thu...or similiar to the past few opc fcsts. Confdc lvls in these gales occurring is close to average.
Seas...both the 12z wna ww3 mdl and 12z ECMWF wam mdl guid appear to have initialized well ovr the off wtrs per the 18z ra1 opc sea state analysis and latest altimeter passes. For the fcst tngt thru Wed we will use a 50-50 blend of the ww3 and ec-wam mdls as a result. For Wed ngt thru the rest of the fcst...we will trend the fcst/grids toward the 12z ECMWF wam WV guid as we switch to using the 12z ECMWF winds for that portion of the fcst.
.Extratropical storm surge guidance...Both the latest estof and etss mdls indicate that a neg surge up to 1 to 2 ft will occur mainly from the VA CAPES northward Mon into Mon ngt in the stronger W-NW wind flow behind the first strong cold front as noted abv. This seem reasonable as we are staying close to the latest GFS wind guid thru the first part of the week. By later in the week as we are leaning towards the slightly slower timing of the next strong cold front crossing the wtrs Wed into Thu...it appears as if the next neg surge could be delayed slightly from what is currently being depicted as we trend the off wtrs fcst toward the slightly slower frontal passage as shown by the 12z ECMWF mdl...which has good support from the 12z UKMET and 12z Canadian glbl mdls.
.Nt1 New England waters... .anz800...Gulf of Maine... gale Mon into Mon night. .Anz805...Georges Bank west of 68w... gale Mon into Mon night. Gale possible Tue night into Wed. .Anz900...Georges Bank east of 68w... gale Mon into Mon night. Gale possible Tue night into Wed. .Anz810...South of New England... gale Mon into Mon night. Gale possible Tue night. .Anz815...South of Long Island... gale Mon. Gale possible Tue night.
.Nt2 mid Atlc waters... .anz820...Hudson Canyon to Baltimore Canyon... gale Mon. Gale possible Tue night into Wed. .Anz915...Hudson Canyon to the great South Channel... gale tonight into Mon night. Gale possible Tue night into Wed. .Anz920...Baltimore Canyon to the great South Channel... gale tonight into Mon. Gale possible Tue night into Thu. .Anz905...The great South Channel to the Hague line... gale tonight into Mon night. Gale possible Tue night into Thu. .Anz910...East of the great South Channel and south of 39n... gale tonight into Mon night. Gale possible Tue night into Thu. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale possible Tue night into Wed. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale possible Tue night into Wed. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale tonight into Mon. Gale possible Tue night into Wed. Gale possible Thu night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Tue night into Wed. Gale possible Thu into Thu night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Thu into Thu night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale possible Tue night. Gale possible Thu night. .Anz835...Inner waters from Cape Fear to 31n... gale possible Thu into Thu night. .Anz935...Outer waters from Cape Fear to 31n... gale possible Thu night.
.Forecaster achorn/Mills. Ocean prediction center.