AGNT40 KWNM 170233
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
933 PM EST Wed Jan 16 2019

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

Per the 00Z NCEP surface analysis a high pressure ridge was
located over the central and southern NT2 offshore waters with
winds less than 20 kt, while to the N west winds were increasing
ahead of a cold front approaching the New England coast. Over
the NT1 waters at 01Z buoy 44037 in the Gulf of Maine reported W
19 with gusts to 23 kt while the somewhat elevated C/MAN MISM1
reported W 27 with gusts to 35 kt.

Don't plan to make significant changes to the ongoing forecast
in place, but did update the near term through 18Z Thu with the
current 18Z GFS preferring the higher first sigma level winds
with strong cold advection as the cold front moves rapidly
offshore tonight, and also leading to freezing spray concerns.
Greatest chance of moderate is near the Maine coast where air
temperatures will be coldest. This gives maximum winds of 30 kt
in the Gulf of Maine tonight. The 18Z GFS/NAM were otherwise in
good agreement with the 12Z guidance through Thu morning with
differences then remaining later Thu through Sat morning in
regards to a weak system expected to pass E across the OPC waters
Thu night Thu Fri night. With the models yet to come to a
complete consensus with this system, feel it's reasonable to
await 00Z guidance before making any potential changes to the
grids for that later Thu through Sat time period. Beyond that
attention then turns to strong low pressure and its associated
strong front approaching, then moving E across the entire OPC
offshore region Sun and Sun night with widespread gales impacting
every zone Sun and Sun night as a result. Will leave previous
grids in place based on old ECMWF which agrees with model
consensus for an initial inland track over the mid-Atlantic
states and then NE across the NT1 waters Sun into Sun night,
somewhat slower than the GFS/NAVGEM, leaving possible storm force
S winds in the NE NT2 waters Sun night.

Updated wave grids with a 3:1 blend of the 12Z ECMWF WAM with the
current 18Z WW3/WNA initially and through 18Z Thu, and leave the
remainder of the grids unchanged.

Please see the previous discussion for additional information.

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PREVIOUS DISCUSSION...

Per the 18Z NCEP surface analysis a high pressure ridge was
located over the OPC offshore waters. ASCAT high resolution
retrieval data, where available, revealed 15-25 kt winds over
much of the NT1 waters, except over the SE parts where 10-15 kt
winds were noted. 10-20 kt winds were noted over the outer NT2
waters.

Upon reviewing the 12Z model guidance I plan to populate the
grids through Thu night with the 12Z GFS, then the 12Z ECMWF
through Fri night, then allow the ongoing grids based off the 00Z
ECMWF to remain in the grids for the rest of the period. Though
some edits by hand will be made over the weekend, concerning the
impacts expected from the strong cold front still anticipated to
pass E through the waters.

High pressure over the offshore waters, weakens over the NT1 and
N parts of the NT2 waters tonight as a cold front over New
England, moves E towards the coast and eventually through the
NT1 and N parts of the NT2 waters later tonight into early Thu.
Model guidance has remained in very good agreement concerning the
timing of frontal passage and strength of this front. Continue
to anticipate winds remaining below warning level criteria as
this front moves through, with the strongest winds expected in
the vicinity of the Gulf of Maine, where we've been carrying 30
kt in the forecast. Differences among the guidance remain Thu
through Sat morning in regards to a system expected to pass E
across the OPC waters Thu night Thu Fri night. Though the 12Z
ECMWF/UKMET are similar with this feature, showing a weak closed
low moving E across the central NT2 waters Thu night into Fri
night as compared to the 12Z GFS which has a weak frontal feature
moving E, to the N, across the N NT2 waters and the NT1 waters. With
the models yet to come to a complete consensus with this system,
had been sticking with an ECMWF solution during this time frame.
For this package will continue with that thinking but will
populate the grids with the 12Z ECMWF Thu night into Fri night,
with confidence still remaining below average in regards to the
exact evolution of this low and or possible frontal boundary.

Beyond that attention then turns to strong low pressure and its
associated strong front expected to approach, then move E across
the entire OPC offshore region Sat night through Sun night. Widespread
gales impacting every OPC offshore zone is expected both ahead of
the front and in the wake of the front in strong cold air
advection. For the last few days now guidance has been fairly
consistent on the idea of said front, and its parent low to the
N, impacting the region during said time frame, with fairly good
consensus concerning the timing and strength of the front. Though
the guidance isn't exactly right on top of one another, it's
consistent enough to where confidence in said widespread gales
are moderate, despite it being day 4 and 5. The overnight
forecast upgraded a few of the outer NE NT2 zones to include
small areas of storm force winds, in the vicinity of the Gulf
Stream, in the very strong S to SW flow ahead of the front
overnight Sun into early Mon. The 12Z GFS/CMC/NAVGEM continue
with this scenario and have pockets of 50 kt surface winds in
their solutions, with the 12Z UKMET/ECMWF both showing areas of
45 kt winds. At the 925mb level for that part of the NT2 waters
Sun night into very early Mon, the 12Z GFS/ECMWF both suggest 70-80
kt winds. For the GFS this is about 10 kt weaker than what it
showed at 06Z but consistent for the ECMWF when compared to its
00Z run. With this noted, the continued expected strength of the
front, high pressure expected to the E, feel it's reasonable to
continue with the storm warnings in the forecast Sun night over
a part of the outer NE NT2 waters.

.SEAS...The 12Z Wavewatch III and ECMWF WAM initialized fairly
well when compared to 12Z and 18Z buoy and ship observations with
values generally within 1-2 feet of the observations. For this
forecast issuance, the choice of wave models will reflect the
choice of models for winds, also meaning for parts of the
forecast where the ongoing wind grids were allowed to remain, the
old wave grids remained as well.

.EXTRATROPICAL STORM SURGE GUIDANCE...No significant positive
surge events appear likely for the next few days.



.WARNINGS...Preliminary.

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

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

$$

.Forecaster Bancroft/Holley. Ocean Prediction Center.