marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 830 am EDT Thu 24 Apr 2014
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
NW winds over outer new engl and NE mid Atlc waters should increase slightly thru afternoon into the evening. Obviously have confidence with gales tda and tngt but moderate confidence that winds will reach storm for a brief period late this afternoon and evening over outer anz910 and anz905 waters. So thru the short term will not be making much adjustment to grids. Mdls have then shown respective run to run continuity with sfc low dlvpg along cold front near mid Atlc coast Fri ngt. 00z ECMWF and 00z UKMET were both stronger than GFS and indicat gales associated with low Sat into sun. In addition past couple runs of GFS have been slighly more progressive and further N with track of low when compared to ECMWF/UKMET. For this mornings update will continue with previously preferred ECMWF/GFS blend. However 00z gefs mean is S of 00z/06z GFS op runs with track and is also has same cntrl pres as op runs so am leaning toward trending forecast more toward stronger ecwmf/UKMET. Will retain previously forecast gales over W and SW quads of low as it moves E along 1000 FM Sat into sun.
10z altimeter overpass along 70w and 69w returned 14 to 16 ft over mid Atlc waters with 19 ft Max invof 36n69w just E of waters. This indicates 00z/06z multigrid wavewatch iii is slightly underdone with sig WV hgts. Will populate with 00z ECMWF wave mdl as a start which is higher than mww3 and make adjustments from there.
---------------------------------------------------------------- ...Previous discussion...
The global models are in pretty good agreement through thr forecast period regarding the track and positioning of forecast lows that will be effecting our offshore waters. In the early part of the fcst gales are occuring as evidence by the most recent ascat pass. As the low intensiifies E of the offshore waters the gale conditions will increase to near storm force in the NW flow...especially in far NE portion of nt2 waters. Once this system exits the region there will be brief respit as a ridge moves across inave of the next low center moving off the Delmarva Fri night. Although all the global models agree on a low forming on the front with pretty much the same track...they differ on the intensity. The UKMET/ECMWF fall into the stronger group...while the GFS/CMC were weaker. I decided to use a blend of the GFS/ECMWF models for the period after 12z Fri and this produced some gale conditions in the offshore waters...although not quite as strong as ECMWF would indicate. I also blend the ww3 and ECMWF wave guidance throughout the forecast period. Through the next 24 hours I populated the grids using the 30m GFS winds with an 10 percent increase on far NE portion of nt2 zones.
.Extratropical storm surge guidance...00z estofs indicating a negative surge more than double that of the 00z etss with values -1.5 to -2 ft from Delaware Bay to Long Island Sound Thu and Thu ngt. Whereas 12z etss is in 0 to -0.5 range. Based on previous cases the estofs is likely overdone with negative surge...with etss or at least a blend of the two seeming more reasonable.
.Nt1 New England waters... .anz800...Gulf of Maine... gale today into tonight. .Anz805...Georges Bank east of 68w... gale today into tonight. Gale possible Sat night. .Anz900...Georges Bank west of 68w... gale today into tonight. .Anz810...South of New England... gale today. Gale possible Sat. .Anz815...South of Long Island... gale today.
.Nt2 mid Atlc waters... .anz915...Hudson Canyon to the great South Channel... gale today into tonight. Gale possible Sat. .Anz920...Baltimore Canyon to the great South Channel... gale today into tonight. .Anz905...The great South Channel to the Hague line... storm today into tonight. Gale possible Sat night. .Anz910...East of the great South Channel and south of 39n... storm today into tonight. Gale possible Sat night.
.Forecaster Clark/Shaw. Ocean prediction center.