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000
AGNT40 KWNM 221358
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
958 AM EDT Tue May 22 2018

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

A weakening stationary front extends from the Virginia-North
Carolina border area eastward over the central NT2 offshore
waters this morning, with high pressure near 40N 64W or east of
Georges Bank moving east, per the 12Z preliminary OPC-NCEP
surface analysis. The 06Z guidance is very similiar to the 00Z
cycle, and we will not make major changes to the ongoing
forecast for the late morning update. We will adjust wind grids
slightly to fit with nearby coastal WFO and TAFB grids a little
better, and also adjust grids to conditions noted just prior to
forecast issuance. Also, scattered thunderstorms are noted
mainly near the stationary front and points to the SW off the SE
coast this morning. Scattered thunderstorms are likely near this
front today, and then tonight and Wed near a cold front moving
SE over the region. Locally very strong winds near or exceeding
gale force and rough seas are possible in and near any of the
stronger thunderstorms over the waters during the next couple of
days.

Seas...Sea heights generally range from 3 to 5 feet over the
offshore waters this morning per the latest observations and
altimeter data. Little change appears needed to the ongoing
forecast for the morning update. We will make a few adjustments
to the previous grids in deference to nearby coastal WFO and TAFB
grids over the region during the next few days.

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

Current Conditions...The 00z ncep surface analysis shows a
stationary front extending roughly E to W across the central nt2
waters and into the Cape Hatteras region. The analysis also
indicates another cold front approaching the northern Gulf of
Maine from the N, with high pressure ridging over the offshore
waters N and S of the stationary front. Latest available ascat
and ascat hi-res passes from a few hours ago show 5 to 15 kt
winds over the offshore waters. Lightning density product data
over the past few hours shows few isolated to scattered showers
and tstms near the 1000 fathoms curve in the central nt2 waters.

Models/Forecast...The 00z medium range models are in very good
agreement across the offshore waters for today and tonight, so
will use a 50/50 blend of the 00z/12z Warw model for the wind
grids during this timeframe to maintain forecast continuity. The
models are also in good agreement for the Wed through Thu night
period, so the 00z gfs 10m/30m solution with the stability smart
tool will be used for Wed through Thu night since it looks like
a representative model solution. The 00z gfs becomes an outlyer
solution for Fri through Sat night, since it is much stronger
than the other models with a northern stream low tracking across
the Gulf of Saint Lawrence. So will use the more consistent and
representative 00z ecmwf for the wind grids for Fri through the
rest of the forecast period. Confidence in the forecast is
average through the forecast period.

Seas...The 00z wna wavewatch and 00z ecmwf wam both initialized
well over the coastal/offshore waters. Will use the 00z
wavewatch for the sea height grids for today through Thu night,
in order to be consistent with the preferred 00z gfs wind grids.
Then will switch to using the 00z ecmwf wam for Fri through the
rest of the forecast period, to match up with the preferred 00z
ecmwf wind grids.

Extratropical Storm Surge Guidance...N/A.


.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
     None.

$$

.Forecaster Mills/Scovil. Ocean Prediction Center.



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