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000
AGNT40 KWNM 300106
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
806 PM EST Sun Nov 29 2020

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

The latest model guidance indicates that a high pressure ridge
centered over the northern nt2 waters will move east of the
offshore waters tonight. Low pressure is still expected to move
northeast over the eastern U.S. tonight through Tuesday. Gale
force winds will spread across the offshore waters from south to
north beginning tonight and lasting into Tuesday with storm force
winds still likely in the vicinity of the Gulf Stream Monday into
Monday night. Another high pressure ridge will then build across
the offshore waters Wednesday into Thursday night. Another low
will then develop near the coast by Friday. For wind grids will
continue to use the current grids throughout the forecast period.
Current warnings look reasonable and few changes should be needed
on the next offshore waters forecast.

For wave height grids will also continue to use the current grids
throughout the forecast period.

.EXTRATROPICAL STORM SURGE GUIDANCE...A modest to a more
significant positive surge event will likely develop from S to N
along most of the E coast tonight into Tue, before winds become
more offshore and the surge subsides by later Tue and Tue night.
The 18z ESTOFS values indicate surge levels up to 2 to 2.5 feet
or slightly higher developing along the northern Mid-Atlantic and
southern New England coasts Mon into Tue. The ETSS is still
showing surge levels about half those of the ESTOFS. For now,
with the strong onshore winds more likely, and the GFS winds
still appearing reasonable over the area, it appears that values
closer to the higher ESTOFS guidance may occur. Please monitor
the latest information from local National Weather Service
offices.

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

Very hazardous conditions are expected to develop from S to N
over the offshore waters tonight, Mon through Tue as a strong low
pressure system impacts most of the eastern U.S. and western
North Atlantic Ocean. Widespread gale force and patches of storm
force winds are expected over the offshore waters tonight into
early Tue night. All marine interests should use extreme caution
during this time period, and use avoidance plans as needed.

Overall, the 12Z models are in very good agreement and remain
fairly consistent across the region tonight into Thu night. We
will populate grids with the 12Z GFS winds tonight into Thu
night, and run the smart tool to place the stronger first sigma
layer winds where the most unstable conditions are likely, and
the slightly less 10 meter winds where conditions will be more
stable, and likely over the cooler SSTs north of the Gulf Stream.
This will result in little change from the past few OPC
forecasts and hazards across the region over the next few days.
Storm force winds remain the most likely near the north wall of
the Gulf Stream, off the central and northern Mid-Atlantic coast
Mon and Mon night, ahead of a strong cold front sliding E over
the region. Widespread, locally strong, thunderstorms will
develop from SW to NE over the NT2 into the southern New England
or NT1 waters tonight through Mon into Tue, with the
thunderstorm chances diminishing with frontal passage Mon night
into early Tue night. Any of the stronger thunderstorms have the
potential to produce winds to storm force or briefly higher and
very rough waves. Hazard-level winds will diminish Tue night in
the wake of the strong cold front, with winds likely holding
below gale force for Wed through Thu night across the region as
high pressure moves rather slowly E off the SE U.S. coast. To the
N, a series of weak cold fronts or low pressure troughs will
move E off the New England and northern Mid-Atlantic coasts
during midweek. Forecast confidence through Thu night is above
average.

For Fri and Fri night, we will trend grids closer to the middle
of the road 12Z ECMWF winds, with the 12Z GFS likely a little too
progressive with the next potentially significant low pressure
system expected to impact waters late in the week and next
weekend. This idea is also close to the latest WPC medium range
forecast. The high will move off to the E of the NT2 waters Fri
into Fri night with the next low pressure system approaches the
SE U.S. coast from the SW. For now, we will not bring winds to
gale force over the waters through Fri night, as models diverge
and confidence in any one solution falls to below average. For
Sat and Sun, days 6-7, we will also cap winds below gale force
for now as there will likely be hazard-level winds somewhere
over the region, but because of the current model uncertainty we
cannot be confident enough to add them to the OPC grids. Please
monitor the latest forecasts over the next few days.

Seas: Both the 12Z Wavewatch and ECMWF WAM have initialized well
over the waters per the latest observations with wave heights
ranging from 3 to 6 ft over the offshore waters per the latest
observations. For the afternoon package, as we are relying on the
GFS for winds we will rely on the Wavewatch guidance for the most
part tonight into Thu night, and add up to 1-2 ft near the north
wall of the gulf stream and near the storm force wind areas by Mon
night into Tue, with waves to 24 to 26 ft or so likely in this
region. As we transition winds more towards the ECMWF guidance by
Fri and Fri night we will transition wave heights closer to the
WAM guidance. We will also cap waves closer to 12 ft to match the
capped winds for days 6-7, or next weekend, with further
adjustments in the forecast likely in the coming days.


.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Monday into Tuesday.
.ANZ805...Georges Bank west of 68W...
     Gale Monday into Tuesday.
.ANZ900...Georges Bank east of 68W...
     Gale Monday night into Tuesday.
.ANZ810...South of New England...
     Gale Monday into Tuesday.
.ANZ815...South of Long Island...
     Gale Monday.
     Gale Tuesday.

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Gale Monday.
     Gale Tuesday.
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Monday into Tuesday.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Storm Monday into Monday night.
     Gale Tuesday.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Monday into Tuesday.
     Gale Possible Tuesday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Monday.
     Storm Monday night.
     Gale Tuesday.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles Light...
     Gale Monday.
     Gale Tuesday.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale tonight into Tuesday.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale tonight.
     Storm Monday into Monday night.
     Gale Tuesday.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale tonight into Tuesday.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale tonight into Monday night.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale tonight into Monday night.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale tonight into Monday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale tonight into Monday.

$$

.Forecaster Nolt/Mills. Ocean Prediction Center.


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