Marine Interpretation Message
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125
AGNT40 KWNM 170812
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
312 AM EST Mon Dec 17 2018

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

The GOES infrared satellite imagery indicates an area of low
pressure tracking E to the S of southern New England, and the
associated occluded front moving across the northern offshore
waters. Ascat wind retrievals from 02Z indicated gales over
Georges Bank ahead of the front, though coastal buoys to the N of
the system show nothing more than 25 kt. However, all of the
observations are fairly well displaced from where Ascat indicated
the higher winds, while the 00Z GFS and ECMWF are both showing
winds in the 25 to 30 kt range in NT1, and 30 to 35 kt in the
cold air advection behind a secondary cold surge over NT2. The
high resolution 00Z ARW is initialized well when compared with
the data, and indicates areas of gales over the Gulf of Maine
and also in the cold advection mainly in the vicinity of the Gulf
Stream. The models maintain the strongest cold advection over
the offshore waters through Tue while indicating several
additional surges behind the main cold front now E of the area.
This matches well with the upper levels as the GFS/ECMWF
indicate a few weak shortwave troughs moving across the northern
zones before a stronger one moves across the area on Tue. The 00Z
guidance is in good agreement on the features in the short range,
so planning on starting out with the 00Z ARW in the next forecast
as it seems representative of the 00Z guidance and also picks up
on some of the more subtle features mainly over the Gulf Stream.
As far as the headlines are concerned, am planning on maintaining
gales across the northern zones today into Tue night as
confidence is above average.

The 00Z models then show high pressure building across the W
Atlc Wed before it passed E of the offshore waters Thu. The 00Z
GFS then indicates another developing low will move N to the W of
the offshore waters Fri as its associated cold front passes E
over the area. The 00Z GFS/ECMWF have been consistent on gales
in the southerly flow over the warmer waters in NT2 as a strong
low level jet sets up ahead of the front and increases the mixing
with the enhancement from the vertical shear. However, the 00Z
GFS is a bit faster with the front than the rest of the 00Z
guidance, and also seems a bit strong with the southerly flow
over the colder SSTs in the Gulf of Maine by late Fri into Fri
night. The previous forecast had gales for mainly the NT2 zones
with the negative static stability expected at that time, and
also over Georges Bank where SSTs are up to 4 degrees Celsius
anomalously warm. This still seems reasonable, especially
considering the models underforecasting with high SST anomalies.
Confidence is about average on gales for starting late Thu into
Fri, so planning on maintaining previous headlines since the 00Z
guidance still supports them. As far as the wind grids are
concerned, am planning on switching to the 00Z ECMWF on Tue
night and continuing with it through the remainder of the
forecast period.

.Seas...A Jason-3 altimeter pass from 0430 UTC this morning
showed wave heights up to 14 ft in nrn NT2 in the vicinity of
cold air advection across the Gulf Stream. It also indicated 14
ft in Georges Bank where Ascat wind retrievals showed a few
gales overnight. The 00Z ECMWF WAM was initialized a bit better
than the 00Z Wavewatch when compared with the data, so planning
on starting out with the 00Z ECMWF WAM in the next forecast. Will
then continue with it through the rest of the forecast period as
it reflects the forcing from the preferred 00Z ECMWF winds.

.EXTRATROPICAL STORM SURGE GUIDANCE...The 00Z ESTOFS has been
within 0.5 ft of current stations along the Mid Atlc and srn New
England coasts this morning in the strong easterly fetch N of the
aforementioned low pressure in the offshore waters. The ESTOFS
shows about 1.5 ft surge in these areas, but subsides the surge
by this afternoon while building to near 1.0 ft along the nrn New
England coast. The ESTOFS seems reasonable in the short range,
but looks a tad fast with the next surge late Fri with the strong
southerly flow ahead of the next strong cold front. Please
monitor coastal flood/tidal products from your local National
Weather Service forecast office for more information.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Kells. Ocean Prediction Center.



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