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AGNT40 KWNM 251848
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
248 PM EDT Thu May 25 2017

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

Over the short term, the new 12Z models have converged towards
very similar forecast tracks for the surface low now approaching
the Nrn mid Atlantic coast to track NE across the Srn New
England coast tonight, pass E across the Gulf of Maine Fri, then
pass E of the NT1 waters Fri night into Sat. The models also
share similar timing for an associated warm front to lift N into
the NT1 waters tonight/early Fri, while at the same time the low
pulls a cold front E across the waters tonight into late Fri. In
regards to the forecast gradients associated with these fronts, N
of the warm front per the now slightly weaker 12Z GFS it looks
more marginal if the previously forecasted Ely gales will develop
in NT1 zone ANZ800 early tonight. But for now with the 12Z
NAM/GEM forecasting slightly stronger Ely gradients and the
usually conservative 12Z UKMET/ECMWF forecasting solid 25-30 kt
boundary layer (BL) winds, will go ahead and continue with this
gale warning. Further S in association with the cold front, with
all of the models forecasting gale force associated BL winds
(which were confirmed by an earlier 1528Z high resolution ASCAT-A
scatterometer pass), forecast confidence is significantly higher
that gales will continue across the central NT2 waters,
primarily in the vicinity of the gulf stream. Therefore, similar
to the previous offshore forecast package for tonight through
Sat, plan on populating our forecast wind grids with our smart
tool that will place stronger 12Z GFS first sigma level winds in
unstable areas and weaker 12Z GFS 10m winds in stable areas
(which will be primarily from the gulf stream northward). So per
these winds, do not anticipate making any major timing and/or
areal coverage changes to the previously forecasted gale
warnings.

In the long range, the 12Z models continue to forecast an ill
defined pattern with weak associated features (with sub gale
force winds). Versus its previous respective runs, the 12Z GFS
is now more progressive in forecasting a weak surface low to
track E along a stationary front across the central NT2 waters
Sat night into Sun night. The 12Z GEM supports this solution, but
the 12Z GEFS Mean indicates that the 12Z GFS is likely too fast
with this low, which is also evidenced by the less progressive
12Z UKMET/ECMWF solutions. The 12Z GFS/GEM are then similar in
forecasting the front to lift slowly Nwd Mon/Mon night with
several weak lows tracking E along the front, while the 12Z UKMET
forecasts a more progressive warm fropa with a stronger
associated frontal wave. Since its less progressive than the 12Z
UKMET and not quite as slow as the 12Z GFS/GEM, the 12Z ECMWF
looks like perhaps a reasonable compromise for this warm fropa.
Then the 12Z global models come into somewhat better agreement
that a weak cold front will approach from the NW Tue, then push
offshore into the Nrn waters Tue night. So since its been
somewhat more consistent, plan on favoring the 12Z ECMWF solution
for this long range pattern and as a result will populate with
its BL winds on Sat night through Tue night.

.SEAS...The slightly higher 12Z Wavewatch III has intitialized
the current seas better than the 12Z ECMWF WAM. With this in
mind and since the 12Z GFS solution will be favored, will
populate our forecast wave grids with 12Z Wavewatch III seas for
tonight through Sat. Then since the 12Z ECMWF solution will
become favored, will transition to populating with 12Z ECMWF WAM
seas on Sat night through Tue night.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale tonight.

.NT2 Mid-Atlantic Waters...
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale tonight into Friday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale tonight into Friday.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale tonight.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
 Gale tonight into Friday.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
 Gale tonight.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale today.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
 Gale tonight.

$$

.Forecaster Vukits. Ocean Prediction Center.



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