000
AGNT40 KWNM 251412
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
1007 AM EDT Sun Oct 25 2020

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

At 12z, a high pressure ridge was located over the New England
and the Mid-Atlantic waters. A cold front stretched from off the
southern North Carolina coast, and NE 36N73W, then ENE to 36N70W.
GOES-16 satellite imagery showed showers and thunderstorms along
the front and to its S over the SE U.S. offshore waters. I will
not be making changes to the ongoing grids in this intermediate
forecast update.

Please refer to the previous discussion below for additional
information.

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PREVIOUS DISCUSSION...

The GOES infrared satellite shows Hurricane Epsilon S of
Newfoundland this morning, and moving quickly off to the NE and
away from the offshore waters. Ascat wind retrievals from 01Z
showed 25 kt winds over the far outer nrn NT2 offshore waters
last night, and the 00Z model guidance indicates the higher
winds
have passed E of the offshore waters at 06Z, and current surface
reports show generally the same. In addition, the latest NCEP
surface analysis shows a weak cold front across the nrn zones,
and the surface reports indicate winds to 25 kt N of the front
in
the cold advection. Ascat from last night indicated a few 25 kt
winds in the Gulf of Maine, with a few higher barbs in the
coastal waters. The 00Z GFS and ECMWF both show the front
stalling over nrn NT2 early today, as high pressure builds N of
the area into tonight. The GFS/ECMWF also agree on the front
lifting back N as warm front tonight into Mon, and increasing
the
pressure gradient between the high and the front. The GFS is
slightly stronger than the ECMWF with the winds, but generally
shows no more than 25 kt to the S of Long Island and Georges
Bank
into Mon before shifting E of the area Mon night. ThE ECMWF is
slightly weaker with the winds, but generally agrees well with
the GFS on the timing and track of the front. In addition, the
models agree on low pressure forming over srn NT2 tonight, and
then show the low moving NE across the central waters Mon before
passing E of the area Mon night and developing further. The 00Z
GFS and ECMWF are also close to the previous wind grids, so
planning on blending them into the previous grids over the short
term.

Going into the medium range, the GFS and ECMWF have trended
towards each other with the next cold front to move over the
area
Tue. The guidance then shows another high moving into the region
on Wed, and the ECMWF has trended faster and is now much closer
to the GFS from the previous run. The GFS timing is also
supported by the 00Z GEM and UKMET solutions, so confidence is
increasing with the 00Z GFS/ECMWF since the models spread is
fairly small through Wed. However, there is also another front
expected to move across the area late Wed into Thu, with a
strong frontal wave developing along it from the remnants of
the tropical system currently in the Gulf of Mexico. There is a
moderately strong signal in the GFS for the development of gales

in the offshore waters near the front and especially near the
wave, and the 00Z ECMWF trended N and towards the GFS solution.
The ECMWF also indicated gales developing in the offshore waters
on Thu, and the 00Z UKMET/GEM shows it as well. However, there
are still some differences on the location of the gales, so
would
prefer to see a more consistent location in the guidance before
adding them to forecast. Otherwise, am planning on continuing
the
blend of the 00Z ECMWF and GFS with the previous grids to trend
the forecast towards the 00Z guidance.

.SEAS...In order to match up with the blend used with the winds,
am planning on using a blend of the previous wave height grids
with the 00Z Wavewatch and ECMWF WAM throughout the forecast
period.

.EXTRATROPICAL STORM SURGE GUIDANCE...The 12Z ETSS and the
ESTOFS
show positive surge developing along the Mid-Atlantic coast today

into Mon night, generally from .5 up to 1 ft from Cape Henry
north to Montauk. With most of the global models echoing the GFS

with relatively strong E-NE onshore winds poleward of a stalled
cold front, these values appear reasonable. Consult your local
National Weather Service coastal office for more detailed
information.

.WARNINGS...Preliminary.

.NT1 New England Waters...
None.

.NT2 Mid-Atlantic Waters...
None.

$$

.FORECASTER HOLLEY/KELLS. Ocean Prediction Center.