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000
AGNT40 KWNM 231406
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
1006 AM EDT Thu Mar 23 2017

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Atlantic Ocean W of 50W from 30N to 50N.

At 12Z strong high pressure was over PA/MD and moves off the
Delmarva coast late this afternoon. Strong winds were along the
eastern areas of the New England into northern Mid Atlantic where
winds were to 30 kt and just E of this area winds were at least
to 35 kt. As the high pressure moves further E into the waters
today the strongest winds will continue to shift E of the area.
By later tonight winds will become light at 20 kt or less
throughout the offshore waters. This period of light winds will
be brief and continue into early Friday. An apparent warm front
will move NE over the northern New England waters. Am not
confident that SWly winds be as strong as 30 kt over the nrn
areas of the New England late on Friday into Friday night. Will
maintain current winds as they are and look for any changes to
12Z model guidance when it comes in. Low pressure will pass N of
the New England waters Friday night and move a cold front S into
the waters. The front stalls S of the New England waters over the
northern Mid Atlantic later Sat into Sunday night...before
lifting back to the N Monday. The GFS has trended towards the
ECMWF with regards to low pressure developing on the front over
the New England waters. As has been the case the past several
days will continue to favor the ECMWF from Friday through the end
of the forecast period.

Seas...At 12Z the ECMWF wam in close to observed seas over the
offshore waters especially along the eastern areas of the
northern Mid Atlantic into the New England waters. The WWIII wave
guidance is about 3 to 4 ft lower than the buoy near Georges
Bank. Will use the 00Z ECMWF wam for today into tonight with no
change to grids from Friday through the end of the forecast
period.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

Summary...The 00z ncep surface analysis shows a 999 mb low
centered over central nova scotia, with an associated cold front
arcing e of the nt1 and nrn nt2 waters. The analysis also shows
a strong high pres ridge building e and se into the offshore
waters. Latest available ascat hi-res and ascat passes from a few
hours ago show 25 to 35 kt winds over almost the entire offshore
waters forecast area, with the 35 kt winds concentrated over the
nt1 and nrn nt2 waters.

Models...The 00z medium range models are in good overall
agreement across the offshore waters for today into fri, so the
representative 00z gfs 10m/30m solution with the stability smart
tool will be used for the wind grids during this timeframe. The
gfs is 5 to 10 kt stronger than the other models with the sw flow
over the nt1 and nrn nt2 waters for later fri and fri night, and
also the 00z gfs is a little faster than most of the models with
the cold front sweeping over the nt1 waters for fri night
through sat night. So the more representative 00z ecmwf will be
used for late fri through the rest of the forecast period, but
with a small wind boost due to the low bias of the ecmwf winds.

Seas...Both the 00z wna wavewatch and 00z ecmwf wam initialized
well over the coastal/offshore waters. The models are in decent
agreement across the offshore waters during the forecast period,
although the 00z ecmwf wam trends a few feet higher with the
seas at times. Will go with a 50/50 blend of 00z wavewatch/wam
through the entire forecast period in order to resolve the model
differences.

.Extratropical Storm Surge Guidance...N/A.


.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale today.

.NT2 Mid-Atlantic Waters...
.ANZ905...The Great South Channel to the Hague Line...
     Gale today.

$$

.Forecaster Rowland/Scovil. Ocean Prediction Center.


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