marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 849 PM EDT Wed Jun 29 2016
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
As a sfc trof conts to push E acrs the ofshr wtrs suspect that the prevly noted 25-30 kt winds are stil present in its advance acrs the outermost cntrl and nern nt2 wtrs. Max seas over these wtrs are lkly in the 6-9 ft range which are in line with the 18z wavewatch iii and 12z ECMWF wam mdls.
Over the short term...the latest mdls remain in good agrmt that the sfc trof and its higher winds wl pass E of the ofshr wtrs by Thu morning. Otherwise wuld favor the smlr 18z/12z GFS and 12z UKMET/ECMWF solutions of a weak cold front pushing se acrs the nt1 and nrn nt2 wtrs tonite into Thu...bcmg stnry acrs the N cntrl nt2 wtrs late Thu/Thu nite...then return N as a warm front Fri/Fri night. So with the 18z GFS fcstg smlr ascd gradients as its prev 12z run...wl cont to use the prev blend of 12z GFS 10m and 12z ECMWF bl winds noted below with just sm minor additional edits in deference to the 18z GFS.
In the long range...overall the latest mdls again share smlr fcst timing for another weak cold front to push slowly ofshr acrs the nt1 and nrn/cntrl nt2 wtrs late Fri nite into Sat nite...then bcm qstnry acrs the cntrl nt2 wtrs sun into Mon nite with prhps a weak frontal wave movg ofshr Mon nite. Again with the 18z GFS rmng consistent...wl cont with the 50/50 blend of 12z GFS 10m and 12z ECMWF bl winds Sat thru sun nite. So then wl cont to transition to using the 12z ECMWF bl winds Mon/Mon nite...but in deference to the slower 18z/12z solutions and slower 12z ecens mean solution wl time shift the winds 6hrs slower Mon nite for the frontal wave movg ofshr (the same time shift wl be done to the 12z ECMWF wam fcst seas on Mon nite).
----------------------------------------------------------------- Previous discussion...
1415z and 15z metop-a and -b ascat overpasses indicated two distinct low pres centers both over the Gulf Stream...near 37n73w and 35n75w. Ascat returned a few areas of S winds to 30 kt also had S winds up to 30 kt over the E semicircle of the southern low as well as outer nt2 waters S of Baltimore Canyon. These ascat winds were slighly higher than 12z models initialized. 12z ECMWF is only global model which initialized two lows...and also is stronger with winds associated with low across northern nt2 waters tonight...with 1/4 deg ECMWF even showing some marginal gales. So for wind grids over next 12 to 24 hours will use a 50/50 blend of the 12z GFS and 12z ecwmf...then increase the blend by about 10 percent to expand area of 30 kt to all outer nt2 zones N of Baltimore Canyon.
12z models as well as 12z gefs and 00z ECMWF eps continued to be in well above average agreement across the W Atlc for the next several days. The weakening cold front should then become nearly stationary off the NC coast late tonight into Thu night before lifting back N Thu night and Fri. Will continue to use a 50/50 blend of 12z GFS and 12z ECMWF through Fri...but again adjust blended winds up by 10 percent to be more in line with deterministic wind speeds. There is excellent model agreement with the timing of the weekend cold front. The GFS and ECMWF have come into better agreement that this front will reach Cape Hatteras and stall Sat night. Do not anticipate any prefrontal winds higher than 25 kt over the weekend. Model disparity increases by early next week with GFS/Gem stronger and less progressive than ECMWF/UKMET with a mid/upper level shortwave moving E through Ohio Valley. 12z ECMWF and 12z UKMET both show the associated surface low moving offshore near the Delmarva Mon night. 12z GFS was a big change from its previous runs which moved a stronger low off the coast earlier. Beginning Mon night am favoring the 12z ECMWF winds.
Latest W Atlc ship/buoy obs are indicating that both the 12z wavewatch iii and 12z ECMWF wam are well initialized this afternoon...and are in reasonably good agreement through the weekend. Plan to populate wave height grids with a 50/50 blend of the above guidance through Mon...then will use the 12z ECMWF wam thereafter.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid Atlc waters... None.
.Forecaster vukits/Clark. Ocean prediction center.