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000
AGNT40 KWNM 220748
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
248 AM EST Mon Jan 22 2018

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

As high pressure currently dominates the offshore waters, an
earlier ASCAT overpass from around 0215Z returned light winds
mostly ranging from 5 to 15 kt over the offshore waters. A front
over the Gulf of Maine is becoming nearly stationary early this
morning, with a weak cold front east of the central NT2 waters
drifting SE, and high pressure centered about 100 nm E of Cape
Fear per the 06Z preliminary OPC-NCEP surface analysis. Overall,
the 00Z model guidance initialized well over the region and has
remained quite consistent, with decent model agreement noted
over the region for the next few days. This leads to above
normal confidence levels in the forecast for the early morning
package.

The main forecast concern will continue to be the extent of gale
force winds expected with the passage of a strong cold front
which will move E over the waters later Tue and Tue night,
pushing E of the region Wed. For the early morning package, we
will populate grids with the 00Z GFS for today into tonight, as
excellent model agreement is noted over the short term. We will
remain close to the 10 meter winds as conditions are expected to
remain fairly stable over the water today into early tonight as
high pressure slowly moves E away from the region. This will
result in little change from the past few forecasts, with just a
refreshing of the grids for the most part into tonight. For Tue
through Wed, we will rely on the previous grids and forecast,
except in deference to the slightly stronger 00Z GFS and 00Z NAM
guidance, expand the previously forecast gale force winds to
include the inner NT2 zones of ANZ820 and 825, or those zones
off the Delmarva coast and Jersey shore. We will also go ahead
and bump up the previous forecast by 5 kt or so, mainly E and S
of the gulf stream, over outer NT2 zones of ANZ910 and 920, with
maximum winds around 45 kt now forecast by Tue eve. Model
guidance shows a low-level 925mb jet over 60 kt in this region
later Tue into Tue night. SREF guidance also suggests an
increase in thunderstorms over most of the NT2 waters Tue
afternoon into Tue night. The thunderstorms will likely help to
mix these stronger winds toward the surface, so we feel
confident in boosting the winds a little higher at this time.
We would not rule out a period of storm force winds especially
near, E and S of the gulf stream by Tue night, especially over
the outer central or northern NT2 waters. The potential for
storm force winds will be the focus of the forecast over the
next day or two. Please closely monitor the latest OPC forecast.
Wind gusts exceeding storm force will be possible in and near
any of the stronger thunderstorms that cross the waters Tue and
Tue night.

For Wed night through Fri night, the 00Z guidance has remained
very consistent from the 12Z cycle of yesterday. As a result, we
see no need to alter the previous grids and forecast during this
time frame. We will make only minor adjustments mainly closer to
the TAFB and coastal WFO boundaries, with no hazards likely from
Wed night through Fri night over the region. A secondary cold
front is still forecast to push SE over the region Wed afternoon
and night, with low pressure still forecast to form along the
front E of the northern NT2 waters early Thu. Any gales
associated with this low should remain E of the waters Thu. We
will monitor this system over the next few days and adjust the
forecast as needed. Otherwise, we still expect high pressure to
build E toward the coast by Fri, and then slide E over the
waters Fri night. The high is forecast to move E of the waters
early Sat, with the next cold front moving E from the midwest
and Great Lakes.

Seas: Per the latest observations and altimeter data over the
offshore waters, both the 00Z Wavewatch and 00Z ECMWF WAM
initialized quite well early this morning, with sea heights
ranging from 1 to 5 feet over the waters. For the early morning
package, we will use a 50/50 blend of the 00Z Wavewatch and WAM
for today, transition toward the previous grids tonight, rely on
the previous grids Tue through Wed, and then use the 50/50 blend
once again Wed night through Fri night over the region, which
appears as if it matches up fairly well with the wind forecast
during that time frame. Very rough seas can occur in or near any
thunderstorms that develop over the waters Tue and Tue night.
Caution is advised, especially during this time period.

.EXTRATROPICAL STORM SURGE GUIDANCE...No major deviation from
the latest surge guidance appears necessary over the next few
days across the area.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Mills. Ocean Prediction Center.



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