000
AGNT40 KWNM 202018
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
320 PM EST SUN 20 JAN 2019

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

This mornings 1420Z and 15Z Ascat overpasses across the offshore
waters confirmed widespread gale force winds east of the strong
cold front. Peak winds observed were 40 to 43 kt over ANZ835,
ANZ925, and ANZ920, all near the Gulf Stream. Winds to 43 kt
were also seen across the Bay of Fundy. The previous OPC wind
grids which were based on a blend of the ECMWF and HiResW/ARW
agreed well with the Ascat data. The 12Z models continue to
consistently initialize storm force winds across the northern
outer NT2 zones, and as a result our confidence with these gale
and storm hazards is well above average. Also, the latest model
soundings still support a deep enough mixed layer to get some
storm force winds to the surface over these warmer Gulf Stream
waters through this evening. The 12Z models are then consistent
in moving the arctic airmass offshore this evening through Mon
night which is expected to be the coldest airmass of this winter
season, with widespread west to northwest gale force winds
persisting across the offshore waters through at least Tue.
Given the current observations across southeast Canada and New
England, the models generally are not initialized cold enough.
The 12Z model soundings unanimously support strong gales, and
even to storm force across the ANZ910 and ANZ920 zones near the
warmer Gulf Stream waters, where the vertical mixing will be
further enhanced. Through 12Z Tue, we populated the wind grids
with 80 percent previous grid and 20 percent 12Z HiResW/ARW
blend. For the strong cold air advection, especially given the
models handle on this airmass, we elected to boost the higher
blended winds by about 10 percent Mon and Mon night. The 12Z
ECMWF continued to be stronger than the 12Z GFS with the peak
winds through the mixed layer at that time. We will include
storm force winds across the ANZ920 and ANZ910 zones late Mon
and Mon night mainly in the vicinity of the Gulf Stream. Our
forecast confidence remains above average with these gale and
storm warnings.

The strong cold air advection will persist into Tue into Tue
night over the waters while slowly shifting eastward as high
pressure builds from the Ohio Valley E and SE, reaching the
coast by Tue evening, and overspreading the waters later Tue
night. The 12Z ECMWF and 12Z GFS have then come into much better
agreement with the timing of the pair of upper level troughs
expected to move off the coast Thu evening and Fri night. The
12Z GFS is now only 3 to 6 hours or so faster than the ECMWF and
UKMET with the associated cold front Thu and Thu night. There is
a high probability that fairly widespread gales will again
develop east of the approaching cold front Wed night into Thu
night, with potential for storm force winds to develop which
would be most likely across the favored ANZ920, ANZ910, and
ANZ925 zones similar to the current cold front. Given some model
disparity with respect to the strength of the low level jet and
subsequent mixing levels, for now we will cap winds at 45 kt.
Forecast confidence with these forecast gales is slightly above
average. By the end of the week, the disparity between the
models increases with the 12Z GFS/UKMET much more amplified and
less progresive than the 12Z ECMWF with the upper trough through
the lower Great Lakes and New England late Fri/Fri night. The
latest ensembles are not offering much support for a solution as
strong as the 12Z GFS. We are favoring the weaker ECMWF at this
time, which is also more supported by the WPC medium range. By
late in the week into the weekend, our forecast confidence
becomes well below average.

.Seas: Both the 12Z Wavewatch and 12Z ECMWF WAM are
significantly underdone with wave heights across the Gulf of
Maine this afternoon. Buoy 44034 just off the Maine coast
observed wave heights as high as 19 ft within the last couple
hours. So although we will be using the higher 12Z ECMWF WAM as
a start for the wave height grids, significant adjustments will
be needed through the near term. Given the uncertainty with the
strength of the pre frontal winds Wed night into Thu night, and
with the ECMWF WAM generating wave heights close to 30 ft in the
southerly flow, we reduced the ECMWF WAM wave height values by
about 10 percent Wed night through Thu night.

.EXTRATROPICAL STORM SURGE GUIDANCE: Water levels from the
Virginia tidewater area north to the New England coast,
including Long Island Sound, are running about 1 ft to 2 ft
higher than predicted levels which suggest that the ETSS and to
a somewhat lesser extent, the ESTOFS, are underdone with the
storm surge impacting the coast this afternoon. Storm surge is
expected to diminish tonight as winds become offshore and
increase with an increasingly negative surge developing later
tonight through Mon. Please monitor the latest advisories,
warnings, forecasts and statements from coastal National Weather
Service forecast offices for more details.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Clark. Ocean Prediction Center.