Marine Interpretation Message
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192
AGNT40 KWNM 180809
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
409 AM EDT Wed Oct 18 2017

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

High pressure will persist to the west of the forecast waters
and a relaxed pressure gradient across the region will keep winds
below gale force threshold. Geocolor satellite images show
mostly clear skies inland west of the forecast waters but mostly
cloudy areas over the southern waters with some convection
confined to the far southern and southeastern waters. This is in
line with inland high pressure and a surface cold front across
the southeastern and far southern waters. Winds are mainly from
the northeast with weaker winds over the north areas and they
increase southward with maximum winds to 30 kt over the southern
waters in the vicinity of the front. NCEP map at 06Z still has
inland high pressure over the southern states that extends its
ridge northeast across the mid Atlantic states into New England
and that has northeast winds to the east which is mainly the
forecast waters. Another high pressure 1030 MB to the east of the
southern waters generates southwest winds to the east of the
region. Low pressure 1003 MB northeast of the waters has its cold
front that stretches southwest into another low pressure 1012 MB
240 NM east of the Baltimore Canyon, front continues southwest
between the two highs, just east of the waters then into the
southern waters. Latest scatterometer pass at 0244Z this morning
indicated areas of 30 kt winds confined to the far southern
portion of zone ANZ935.

Models GFS/CMC/UKMETHR/ECMWFHR/NOGAPS/NAM/GFSMEAN have
initialized the 06Z main synoptic features fairly well with just
minor differences on the actual position for the central pressure
value of the inland high and UKMETHR is the only model that does
not have a closed low just east of the Baltimore Canyon but a
deep trough. Models have trended weaker and have pushed highest
winds that were east of the forecast waters farther east. In the
short term, models have a general agreement on keeping high
pressure just west of the region and that will block strong
frontal boundaries from reaching the waters and so the pressure
gradient will remain relaxed over the waters through the forecast
period. The models have also indicated some instability to
persist over the southeastern waters as indicated by the
persistent negative lifted index and that will sustain some
mixing that will keep winds relatively higher to the southeast of
the Gulf stream with maximum winds over the far southern waters.
Will continue with GFS for consistency and also that models are
in generally good agreement.

.SEAS...Seas are relatively smaller to the north of the Gulf
stream with 6 ft along the gulf stream and just 2 ft over the far
northwest waters. Otherwise, seas mostly range between 6 and 9 ft
except the southeastern zones where seas are over 9 ft with a
peak at 13 ft. Jason 3 pass about 1908Z returned peak significant
wave height of 13 ft over the southeastern waters. NWW3 generally
fits very well the observed seas pattern but just underdone by a
foot on the peak value. ECMWFWAVE matches the peak value but not
so much in line with observations to the north as it extends its
6 ft line farther north of the gulf stream. As such, an equal
blend of the two wave models is a better compromise and so will
go ahead with a blend.

.EXTRATROPICAL STORM SURGE GUIDANCE...n/a.

.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
     None.

$$

.Forecaster Musonda. Ocean Prediction Center.



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