marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 856 PM EDT Wed Jul 29 2015
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
A quiet pattern persists acrs the wtrs as a weak high pres ridge acrs the cntrl nt2 wtrs is maintaining weak gradients thrut the cstl/ofshr wtrs with Max winds gnrly in the 10-15 kt range...or less. These weak winds are sprtg Max seas of only 4-6 ft...highest acrs the srn nt2 wtrs...which are being handled comparably by the 18z wavewatch iii and 12z ECMWF wam.
Over the short term...the latest mdls cont to differ in their fcst strength of a sfc low fcst to track NE acrs the nt2 wtrs Thu thru Fri nite. The 18z GFS is smlr to its prev 12z run but fcsts a slightly stronger sfc low with sm gale force ascd 30m bl winds over the immed se quadrant of its fcst low...which is smlr to the 18z 4km NAM and 12z Gem. The 12z UKMET is smlr to the 12z/18z GFS solution...but smwht weaker. The 12z ECMWF fcsts its sfc low to weaken into just a sfc trof Thu nite/Fri. Wuld not be shocked to see this system turn into a tropical cyclone smlr to what Claudette prevly did. But for now as a compromise btwn the stronger 18z GFS and weaker 12z ECMWF solutions wl stay the course with the prevly populated 12z GFS 10m bl winds thru the short term.
In the long range...weak cold fronts movg to or just off the new engld and nrn mid Atlc coasts before wkng Sat nite/sun and then late Mon/Mon nite wl sprt a mod strong sswly gradient thrut much of the ofshr wtrs which wl be accentuated by the Bermuda high strengthening smwht. The prev fcst package contd to use the 12z GFS 10m bl winds thru the long range which stil looks representative. But by late sun thru Mon nite plan on blending these winds 50/50 with the 12z ECMWF bl winds as a better compromise then. So as a result wl also do the same 50/50 blend with the 12z wavewatch iii and 12z ECMWF wam mdls for the fcst seas then.
----------------------------------------------------------------- Previous discussion...
Summary...12z NCEP sfc analysis shows a hurcn force low cntrd well E of the ofshr areas near 40n58w...with ascatb-hires pass at 1430z indicating 65 kt winds with the low and obsvtn wdg4279 near 41n56w at 18z shows a 70 kt wind with 22 ft sea hts. Stnry fnt extndg over the srn nt2 wtrs and a weak cold fnt just N of zone 800 in the nt1 wtrs...but otherwise weak hi pres rdg prevails across the ofshr wtrs. Latest avail ascatb- hires passes from this mrng show S to SW winds of 20 to 25 kt over the outer zones of the srn nt2 wtrs...but light winds 15 kt or less across the ofshr wtrs N of Cape Hatteras. Lightning density data at 1850z this mrng shows areas of sct showers/tstms arnd the stnry fnt in the srn nt2 wtrs. Weak cold fnts will move across the nt1 and nrn nt2 wtrs this evng and tonite...Fri into early Sat...then again Sat nite and sun. A stgr cold fnt is expected to move se and aprch the ern Seaboard Mon nite.
Models...the 12z Med rng mdls are in gud overall agreemnt across the ofshr wtrs thru the fcst prd. The UKMET which had been an outlyer soln yday...has now converged into close agreemnt with the GFS. The GFS conts to look vry representative and has had gud run to run consistency...and also it has gud support from the latest wpc Med rng fcstr guidance. The 12z GFS 10m soln looks like a gud median soln btwn the 12z GFS 30m and 12z ecwmf...so it will be used for the wind grids thru the entire fcst prd.
Seas...wna version of the 12z wavewatch iii mdl and 12z ECMWF wam both initialized well over the ofshr wtrs versus latest buoy obs and Jason passes. The mdls are in gud overall agreemnt for most of the fcst prd...and the 12z wna wavewatch iii mdl will be used for the sea ht grids thru the fcst prd in order to match up with the preferred GFS atmos mdl.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid Atlc waters... None.
.Forecaster vukits/Scovil. Ocean prediction center.