Marine Interpretation Message
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
AGNT40 KWNM 230026
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
726 PM EST SUN JAN 22 2017

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

A strong low pressure system will impact the offshore waters
during the next 48 to 60 hours.

No change to the previous headlines appears necessary for the
evening update as the 18Z GFS and NAM models are fairly similar
to their 12Z cycles. We will, however, bump up winds to 55 KT
just south of Long Island for later Monday to fit a little better
with the adjacent coastal WFO forecast, where they have issued a
Hurricane Force Wind Warning, for these very strong winds in
gusts Monday afternoon into Monday night. We will closely examine
the 00Z guidance once it arrives later this evening to see if OPC
needs to upgrade the current storm warning to a hurricane force
wind warning.

The latest radar, satellite and lightning density data indicates
strong thunderstorms occurring over most of the southern NT2
offshore waters this evening, from the Georgia and Carolina
coasts eastward into the offshore waters. For the evening update
we will add higher winds in or near the stronger thunderstorms to
the ongoing forecast, and also attempt to fit the forecast with
the current conditions and nearby WFO and TAFB grids. Otherwise,
we will not be making major changes to the previous forecast and
headlines at this time, with gale to storm force winds likely
over most of the region during the next couple of days.

Widespread thunderstorm activity will likely impact most of the
southern and central NT2 waters tonight, and most of the NT2
waters Monday into Monday night. Extreme caution is advised in
and near the stronger thunderstorms impacting especially NT2
waters over the next 24-36 hours.

Seas...Sea heights will be adjusted to fit current conditions, but
otherwise, we see no need for major changes to the ongoing OPC
forecast at this time. Locally very rough seas can be found in or
near the stronger thunderstorms, especially over southern into
central NT2 waters tonight, and most most of the NT2 waters
Monday into Monday night.

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

Over the short term...In regards to the overall synoptic pattern,
the new 12Z models remain consistent verus their previous
respective runs. The models are in good agreement that the low
pressure center now tracking E across the NT2 waters along a
stationary front will pass E of the area tonight while weakening.
But at the same time tonight as high pressure builds in from the N
and a cold front pushes off the SE coast, per a consensus of the
12Z models expect gale force Ely and SSW gradients to develop N of
the stationary front and E of the cold front, respectively. Then
in response to a closed upper low forecast to swing towards the
mid Atlantic coast, the 12Z models now share similar forecast
tracks for a strong associated triple point surface low (a
nor`easter) to develop and move NNE off the mid Atlantic coast
late Mon/Mon night causing the Ely gradient N of its Nwd moving
warm/occluded front to strengthen further to storm force. Then
Tue/Tue night would favor a compromise 12Z GFS/UKMET/ECMWF
solution (which is supported by the 12Z GEFS Mean) for the low to
track NE across the NT1 waters while pulling a trailing cold front
SE across the NT2 waters. Per the 12Z GFS/UKMET/ECMWF, still
expect the associated occluded front to bow far enough NE that the
associated gales will shift NE of the NT1 waters by Tue night,
while postfrontal WNW gales develop late Tue/Tue night in the
vicinity of the gulf stream across the outer central NT2 waters.
Therefore with the 12Z models remaining consistent for tonight
through Tue night, do not plan on repopulating the previous
forecast wind grids, which were a 00Z GFS 10m/first sigma level
mix, and will just continue to make some additional edits in
deference to the 12Z GFS/UKMET/ECMWF. So as a result do not
anticipate making any major short term timing and/or areal
coverage changes to the previously forecasted gale/storm warnings.

In the long range, the 12Z global models generally agree that
the most significant weather feature will be cold front forecast
to push SE across the waters late Wed night into Thu night (with
gales likely developing near the gulf stream across the NT2 waters
Thu/Thu night), followed then by a series of surface troughes
passing SE across the Nrn waters in the WNW postfrontal gradient.
Overall would favor the similar 12Z GFS/ECMWF solutions for this
long range pattern. So to smooth out the minor timing and strength
differences, plan on populating our forecast wind grids with a
50/50 blend of the 12Z GFS (using our smart tool to place 10m
winds in stable areas and first sigma level winds in unstable
areas) with the 12Z ECMWF boundary layer winds for Wed through
Thu. Then as the cold air advection sets in, will transition to
populating with a 50/50 blend of the 12Z GFS first sigma level
winds and 12Z ECMWF boundary layer winds on Thu night through Fri
night.

.Seas...Since the previous official wind grids will be used for
tonight through Tue night, will not be repopulating the
previously blended 00Z Wavewatch III/00Z ECMWF WAM forecast seas.
Then since a compromise 12Z GFS/ECMWF solution will be used for
Wed through Fri night, will then populate our forecast wave grids
with a 50/50 blend of the 12Z Wavewatch III/12Z ECMWF WAM.

.Extratropical Storm Surge Guidance...In the strong Ely gradient
forecast to develop N of the front tonight and then shift Nwd
through Mon night, the 12Z ESTOFS remains consistent in
forecasting a slightly more significant surge (up to 3-4 FT,
which may be somewhat too low) to develop Nwd up the coast from
Delaware to SW New England than forecast by the 12Z ETSS. Would
continue to favor the higher 12Z ESTOFS solution.


.WARNINGS...Preliminary.

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

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

$$

.Forecaster Mills/Vukits. Ocean Prediction Center.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.