marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 752 PM EST Wed Nov 25 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
No significant changes to the fcst anticipated attm.
High pres over the nrn waters combined with a stationary front to the the E of the area is currently producing winds in the 20 to 30 kt range over the se portions of the nt2 waters. Looks like any sustained gales will remain E of the offshr waters...with gusts to gale force possible over portions of the se nt2 waters.
Over the nrn waters...quieter conditions are currently observed as high pres dominates the region.
Seas...wna version of wwiii still about 1 to 2 ft underdone off the Carolina coast. Will make necessary adjustments to the grids to account for current conditions. Otw...seas within a ft or two elsewhere across the cstl/offshr waters.
----------------------------------------------------------------- Previous discussion...
14z high resolution ascat-a returned NE 25 kt over eastern most portions of mid Atlc outer zones S of 34n. Anomalously strong high pres along the Maine coast will continue to strenghten this afternoon into Thu while stationary front E and se of Bermuda retrogrades westward. 12z models in good agreement that NE winds to 25 kt should expand in coverage over nt2 waters tonight. Earlier ascat confirmed the NE gales E and se of Bermuda and based on strength of high to the N would not be surprised to see some storm force winds develop just N of front from 45w to 55w. For offshore winds opc preference remains with slightly stronger GFS 30m winds through Thu night which does show some 30 kt over outer waters beginning tonight. Models differ Fri into the weekend as to how far W the front will retrograde toward mid Atlc waters. 12z NAM and 12z global Gem continue to be outliers with their agressive depiction of sfc low development along the front and associated gales into offshore zones...and will be disregarded. 12z UKMET and 00z ECMWF are much weaker with front and indicate front should stall again just W of Bermuda and hence are weaker with offshore winds. 12z GFS looks like a compromise between two model camps. Will blend GFS and ECMWF Fri through Sat night and limit winds over southern nt2 zones to 25 kt which is slightly weaker than 12z GFS.
Over past few cycles models have come into better agreement with timing of the cold front to move off the New England coast early Sat. Also 12z GFS has now come in line with UKMET and ECMWF... that is weaker with Post frontal winds over New England waters Sat. The previously preferred GFS 30m and ECMWF blend looks OK for winds Sat and Sat night. There is moderate agreement among models that this weakening cold front will stall near Cape Hatteras sun and Sun night. Then as high pres again builds se off the New England coast winds immediately N of stalled front should increase Mon and Mon night. GFS and ECMWF look reasonable with limited area of N winds to 25 kt at that time.
.Seas...Already have some 6 and 7 ft buoy reports off NC and SC coasts this afternoon...about 2 ft higher than either multigrid wavewatch iii or ECMWF wam. This trend is likely to continue over the near term as the NE 25 kt winds offshore from Hatteras southward expand in coverage tonight and Thu. Will add about 10 percent to models significant wave heights over these areas tonight thru Thu night.
Mww3 and ECMWF wam both indicate longer period E to se swell will move into mid Atlc waters Thu and southern new engl waters late Thu night and early Fri. Mww3 showing slighly longer periods and about three to six hours faster with swell than shown by ECMWF wam.
.Extratropical storm surge guidance...Given the persistent E to NE winds expected from Cape Lookout to the FL coast into Fri... the surge indicated by estofs of about 1.0 along the coast looks reasonable. Past several runs of etss do not seem to be capturing this.
.Nt1 New England waters... None.
.Nt2 mid Atlc waters... None.
.Forecaster achorn/Clark. Ocean prediction center.