marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 343 PM EDT Mon Sep 22 2014
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Cold front moving E across the offshore waters this afternoon will move E of the waters by Tue mrng...shooved se by strng high pres building in FM the NW. Scatterometer pass FM 15z today showed mod winds N of balt cnyn...which were closer to the GFS 30m winds.
Fcst condifedence soon takes lowers significanly as the models differ with the fcst of the an inverted trough and/or sfc low to dvlp off the se coast Tue/Tue ngt and psbly off the mid Atlc coast Wed. Aloft...the models are in fairly decent general agreement overall but the dffrncs in the details is making for the sig dffrnc on the placement and dvlmnt of sfc trof/low scenario. All models agree on upr low closing off ovr the se states by tngt... mvg E...then turn NE Tue and opening up. Each models difers on the placement of S/W energy shearing and/or mvg out to the NE as the main trof retrogrates wwrd.
On the sfc...the on and off sfc low depends on the model and the model run. The models agree on broad sfc trof dvlpng off the coast Tue...and xtndng NE to httrs cnyn by 12z Wed. The GFS/NAM favor a trof closer to the coast while the UKMET extends the trof fthr eastward and the ECMWF has the a weaker trof slgtly inland. Models...GFS/UKMET/Gem in general agreement in a 20 to 30 kt NE gradient just W of the front. The fcst dffrncs incrs in time as the GFS/Gem dvlps a gale just E of the mid Atlc coast while the UKMET and NAM favor a weaker low. The ECMWF remains the flattest... dvlpng a weak low E of the mid Atlc coast Fri. The GFS ll vort hint that it may hv some gridscale feedback here. Considering the gefs only gives wk support to the oprnl GFS...the GFS and Gem solution are cnsdrd a strong outlier. Since the UKMET takes The Middle Ground inbeteeen the strngr GFS/Gem and the much weaker ECMWF...will use blend it and blend in the UKMET Tue...then use it 100 pct for Wed through Sat ngt...with condifence starting out low to mod and decreasing in time. This will kp an area of mod E to NE winds off the mid Atlc and just off the se coast for Wed into Fri...with lgt winds ovr the nrn waters.
.Seas...Is major forecast prblm nbr two. Today...the 12z multigrid wavewatch initlzd well with the subsiding seas in the wake of gale cntr and cold front. Guidance looks good tngt and Tue...then GOES downhill as there is not a UKMET wav model to fllw. Will incrs seas 25 to 45 pct in the NE flow off the se coast Tue ngt and Wed as the models usaually underdoes seas in mod NE flow... against the Gulf Stream. Since a UKMET wave model is not avbl...will blend the wave watch and ECMWF wam...placing more weight...likely 60 to 80 pct on the wam. Will manually adjust seas accrndg to the winds when and where psbl.
.Extratropical storm surge guidance...On Wed...the 12z estofs fcsts a positive surge of 1 to 2 ft FM Long Island S...and 2 to 3 ft along the mid Atlc coast Wed ngt into Thu...before slowly dmnshg later Thu into Sat. The etss models has values to 1 ft. Since the GFS is not the preferred modle aft Tue ngt...neither gdnc looks reasonable.
.Nt1 New England waters... None.
.Nt2 mid Atlc waters... None.
.Forecaster prosise. Ocean prediction center.