marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 318 am EDT Tue Jun 27 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
02z ascat winds from late last night indicated variable winds up to 15 kt over a majority of the offshore waters, and a very small area with up to 20 kt over the srn nt2 waters in the vicinity of a weak frontal boundary. The infrared satellite imagery indicates cloud tops becoming colder over srn nt2, and the lightning density product indicates convective activity developing along the front. GFS stability indices indicate a marginally unstable environment over central and srn nt2, and the sref indicates tstms will continue with this boundary as it moves slowly to the east. Will maintain mention of showers and tstms in the next forecast as a result. In addition, the 00z GFS/ECMWF/UKMET/Gem all indicate an upper trough currently over the Great Lakes will move east into the area over the next 24 hours or so and take the front to the east while developing it. The models agree fairly well on the timing, and all show stronger winds ahead of the front after it passes to the east of the area. The GFS indicates no more than 20 kt over the offshore waters with this feature, and the rest of the 00z guidance agrees with the GFS on timing and intensity. Will start out with the 00z GFS 10m winds in the next forecast, but will use the first sigma winds over unstable areas to account for the slightly deeper mixed boundary layer.
The 00z models then indicate several weak surface boundaries will move through nt1 into Wed, before a high pres ridge builds across the nt2 waters Wed into Thu. The models remain in good overall agreement on the synoptic pattern through Thu, so will continue with the 00z GFS which seems representative of the overall consensus. The 00z models then indicate a cold front will approach from the NW Thu night before low pres passes north of the offshore waters Fri which pulls the front across the area. The GFS is a little slower than the 00z ECMWF with the low passing to the north, and also with the next frontal system approaching from the W on Sat. The 00z UKMET/Gem has trended towards the faster ECMWF solution, and although the timing difference is slight, the 00z GFS is a bit of a slow outlier. As a result, am preferring the 00z ECMWF solution from 00z Sat Onward.
.Seas...The 00z wavewatch and ECMWF wam are well initialized when compared with current observations that indicate up to 4 ft seas in the W Atlc this morning. The models agree generally well throughout the forecast period, so will use a 50/50 blend of the two solutions.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid-Atlantic waters... None.
.Forecaster Kells. Ocean prediction center.