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AGNT40 KWNM 270207

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
1007 PM EDT Fri May 26 2017

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

At 00Z low pressure is analyzed near Cape Sable with a 998 mb
pressure and a low pressure trough extending SW from the center
to Cape Cod. The associated frontal system with gales has moved
well E of the offshore waters. The latest models are initialized
well with this low and are in agreement showing strongest winds
20 to 25 kt in the westerly flow S of the trough and over the
central NT2 waters along and S of the Gulf Stream. For the
evening update with overall model agreement with the pattern
evolving into a weak zonal flow with weak gradients especially
from later Sunday on, the current wind grids using the 12Z GFS
with the 10m_30m stability tool look reasonable. The only change
made is to the near term overnight with wind grids repopulated
with the 12Z ECMWF with its 10m boundary layer winds boosted
along and to the south of the Gulf Stream to have conditions more
closely match recent buoy observations east of the North Carolina

Seas...Although the first period wind grids are repopulated with
the 12Z ECMWF, chose not to repopulate with the associated wave
model as the 12Z NWW3 closely matches the 00Z sea state analysis,
and appears representative and will be retained through the
forecast period.

The gale warnings in the NT2 zones have diminished and no
warnings are expected through the forecast period. The satellite
images still show cyclonic circulation in the vicinity of the NT1
waters and clouds with cold tops still covering the north
waters. The lightning density map continues to show intense
lightning northeast and east of the region associated with a
front that extends from the circulation. Highest winds are now
just below gale force range over the northern waters of NT2. At
1800Z the NCEP map has low pressure 996 mb over maine waters that
has an occlusion stretching northeast. High Pressure 1026 MB
near 31N50W still extends a weak ridge into the far southern
waters. The pressure gradient over the north waters has relaxed.

In the upper levels, the models GFS/CMC/ECMWFHR/UKMETHR indicate
upperlevel cut-off low with some energy embedded in it over the
north waters. An upper level ridge extends north across the
southern waters and just west of the central and northern waters.
In the short term the models suggest the ridge will persist west
of the region then slowly drift east into the waters in the
extended period. As such, the synoptic pattern over the region
will not vary much and there will only be little variations in
the resultant winds.

The models GFS/CMC/ECMWFHR/UKMETHR have initialized well the
1800Z surface observations with just minor differences still on
the actual location of the low pressure center over the maine
waters. The models also have slight differences on the areal
coverage of the gale force winds just east of the region. ECMWFHR
and UKMETHR are still weaker than the observed winds while CMC
is stronger than GFS and the observed winds. Will stay close to
GFS guidance.

.SEAS...The seas are largest over the Baltimore canyon with a
peak at 16 ft. Seas range between 9 and 15 ft over the north and
central waters while they range between 3 and 9 ft over the
southern waters with smallest seas over the southwest portion.
The wave models NWW3 and ECMWFWAVE have matched well the observed
seas pattern and both wave models have shown consistency in the
previous runs.



.NT1 New England Waters...

.NT2 Mid-Atlantic Waters...


.Forecaster Bancroft/Musonda. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.