Marine Interpretation Message
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000
AGNT40 KWNM 241308
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
808 AM EST Fri Nov 24 2017

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

The latest model guidance indicates that low pressure currently
east of northern Florida will track northeast across the southern
nt2 waters today into Saturday. Minimal gales are still expected
across the southern nt2 waters today and then should remain just
east of the nt2 waters tonight into Saturday night. Northwest
flow will then increase across the northern portion of the
offshore waters by Sunday with winds still expected as high as 30
knots or so. Mainly light winds are then expected across most of
the offshore waters by Monday night as strong high pressure moves
off the Mid Atlantic coast. A cold front will then approach the
New England coast by Tuesday night with minimal gales possible
across the far northern nt1 waters. The front will then move
across the nt1 waters by Wednesday night. For wind grids will
continue to use the current grids throughout the forecast period.
Current warnings look reasonable and few changes should be needed
on the next offshore waters forecast.

For wave height grids will also continue to use the current grids
throughout the forecast period.

Extratropical storm surge guidance...n/a.

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PREVIOUS DISCUSSION...

Geocolor satellite images still show cold clouds over most of
the region with lightning density map showing TSTMS moving
northeast across Florida and now entering the far southern
waters. Satellite images also continue to show fewer clouds
across New England and the mid Atlantic states which is in line
with the observed surface features. At 06Z the NCEP weather map
has a cold front to the east of the region that turns into a
nearly stationary front as it enters and lies across the far
southern waters. High pressure 1019 MB over waters adjacent to
Virginia has ridges into the northern and central waters.
Pressure gradient is still very relaxed across most of the region
except near the frontal boundary over the southern waters. Winds
are mainly from the west over the north waters and from the
north and northeast over the rest of the region. Higher winds in
gale force range are confined to the southern waters in the
vicinity of the stationary front.

In the upper levels, an upper level ridge extends northeast from
the southwestern states while an upper level trough lies just
west of the forecast waters across the great lakes into the
southeastern states. There is some energy embedded in the upper
level trough that will pass east over the waters in the short
term. Another upper level trough will approach the waters and
bring some energy especially to the northern waters Sunday.
Currently there is energy associated with surface storm warning
in the Gulf of Alaska that will eventually track through Canada
and reach the northern waters toward the end of the period and
both ECMWFHR and GFS are in a good agreement on timing of this
energy. So with moderate confidence, will initiate gale warnings
over the far northern waters in the extended period.

Models GFS/CMC/NOGAPS/UKMETHR/ECMWFHR/NAM have initialized the
06Z surface observations fairly well especially over the forecast
waters. In the short term, models generally agree on low
pressure moving northeast from the Gulf of Mexico into the
southeastern portion of the southern waters but differences are
on the actual track of the low center. The models have difficulty
in locating the center as low pressure moves into the waters.
More models suggest a complex low over the southeastern waters.
The position of the low center will help to determine if winds
will reach gale force over the waters. For this issuance, I plan
to just retain the previous models choice which is using GFS
initially then switch to ECMWFHR.

.SEAS...Seas are generally small across the region with a peak at
8 ft over the Baltimore Canyon. Seas range between 3 and 6 ft
over the western half north of 34N while they range between 6 and
7 ft over the rest of the area. NWW3 and ECMWFWAVE models agree
well with the observed 06Z seas pattern. The wave models agree in
the short term on keeping seas less than 8 ft across the region
but will be relatively higher over the northern waters. Will just
use the NWW3 guidance in the short term and extend seas 5
through 7 days with ECMWFWAVE.

.EXTRATROPICAL STORM SURGE GUIDANCE...Storm surge from Georgia to
North Carolina will be positive but less than a foot. This is
in response to the gales in the vicinity of the front and so the
surge will quickly subside by tonight.


.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Possible Tuesday night.

.NT2 Mid-Atlantic Waters...
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale today.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale today.

$$

.Forecaster Nolt/Musonda. Ocean Prediction Center.



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