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000
AGNT40 KWNM 230806
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
306 AM EST Sun Feb 23 2020

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

Over the short term, the 00Z models remain very consistent and in
excellent agreement. We will populate grids with the
representative 00Z high resolution Wnmm winds today through Mon,
which will result in little change from the past few OPC
forecasts, with hazard-level winds unlikely over the short term.
ASCAT overpasses from last evening indicate moderate winds up to
25 kt or so occurring roughly along 40N or so, from S of Long
Island eastward, with winds of 20 kt or less elsewhere as high
pressure builds E over waters from the Delmarva coast southward,
and low pressure troughs cross waters N of the Delmarva today
into tonight. By later tonight and Mon we still expect the high
to begin shifting E of the waters, with a weak cold front moving
SE over New England during the day Mon. Forecast confidence over
the short term remains above average.

Over the medium range, Mon night through Thu night, a more active
wather pattern will likely develop over the region, with the
overall scenerio remaining consistent across the offshore
waters. A cold front will move SE over the Gulf of Maine Tue as
a warm front develops from the Delmarva eastward, as high
pressure moves E from near Bermuda, and low pressure tracks E
from the Ohio Valley. The cold front will merge with a
stationary front extending eastward from the northern Delmarva
Tue night. The front will persist in this same general area Wed
as low pressure forms over Delaware or southern New Jersey. The
low will strengthen and move NE along the New England coast Wed
night with the warm front lifting N and a trailing strong cold
front moving E over the offshore waters. The cold front will
clear E of the waters early Thu as the low moves from coastal
Maine towards New Brunswick, Canada. A secondary cold front will
cross the water Thu night as the low moves NE over the Canadian
Maritimes with strong cold air advection likely over the region
by Thu night. Again, the main concern over the medium range
continues to be the potential for gale force winds across the
offshore waters. The 00Z GFS and 00Z ECMWF remain in generally
good agreement over the region Mon night into Tue night, and we
will use an even blend of these two models during this time
frame, and use the first sigma layer winds from the GFS for the
blend which will serve to enhance winds somewhat Mon night into
Tue night, but keep winds below gale force, which at this time
appears the most likely. For Wed through Thu night, we will then
transition grids more toward the very consistent 00Z ECMWF winds
which are about in the middle of the overall model consensus,
with the 00Z GFS trending a little faster with the low verses
the remaining guidance. We will boost the ECMWF winds by 10
percent or so in the gulf stream, with the ECMWF winds known low
wind bias especially in and near the warmer SSTs of the gulf
stream. This will allow for winds to approach gale force Wed
over the outer southern NT2 waters, but we prefer to keep them
just below gale force for now until better model agreement
develops. We will, however, go ahead and add gale force winds
possible to outer central and northern NT2 waters near the north
wall of the gulf stream Wed night, where the stronger, enhanced,
winds currently appear the most likely, and then also for the
Gulf of Maine where strong onshore winds are likely just ahead
of the warm front and approaching low pressure area, with
current guidance indicating that these areas have the best
chance for gales for Wed night and early Thu. Strong cold air
advection is then forecast to develop over the waters by Thu
night, with the best chance for gales currently expected to
again be near the north wall of the gulf stream, or over NE NT2
waters. Therefore, we will go ahead and add gale force winds
possible to these waters for the early morning package. Overall,
forecast confidence remains above average over the medium range,
and near average for the possible gale force winds. Additional
adjustments to these hazards can be expected over the next few
days, and all marine interests should closely monitor the latest
OPC forecast.

.Seas: Seas heights early this morning range from 8 to 10 ft over
the outer southern NT2 waters, to 4 to 7 ft over the New England
waters. It appears that both the 00Z Wavewatch and 00Z ECMWF WAM
guidance have initialized well over the region early this
morning. For the early morning package, we will use an even
blend of these two wave models for today into Tue night. For Wed
through Thu night, we will then trend sea heights more closely
toward the 00Z WAM, but add up to 10 to 15 percent mainly in and
near the gulf stream and gales over the Gulf of Maine as the WAM
guidance typically underperforms in these areas, with these
stronger winds.

Extratropical Storm Surge Guidance: No significant positive
surge events are expected over the next few days. A moderate
positive surge event may develop mainly from the northern New
Jersey coast northward by later Wed into Thu as strong onshore
winds develop. For more detailed forecasts and information,
please use information provided by your local coastal National
Weather Service forecast offices.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Possible Wednesday night into Thursday.

.NT2 Mid-Atlantic Waters...
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Possible Thursday night.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Possible Wednesday night.
     Gale Possible Thursday night.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Possible Thursday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Possible Wednesday night.
     Gale Possible Thursday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale Possible Wednesday night.

$$

.Forecaster Mills. Ocean Prediction Center.



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