Marine Interpretation Message
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
AGNT40 KWNM 250131
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
931 PM EDT Wed May 24 2017

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

No significant changes anticipated to the forecast or headlines in
the next package.

Latest surface observations showing winds below gale force at
this time. However, there are currently no observations near
potential gale area in NT2 waters. Latest global model guidance
continues to show enhanced southerly winds developing ahead of a
cold front to move off the southeast coast later tonight into
Thursday. Highest winds look to be in and near the gulf stream
where the greatest instability is located, and will allow for
gales to mix down to the surface. Current headlines look good for
now and do not plan on making any significant changes to them.

SEAS...WNA within a foot or two of current obsevations. Had
recent ship report of 10 ft off North Carolina coast. Expect
building seas overnight to near 14 ft by morning.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

Over the short term, overall the new 12Z models are in excellent
agreement. The models share very similar forecast timing for a
cold front to push off the SE coast into the SW most NT2 waters
tonight, then continue E across the waters Thu/Thu night. In the
meantime, with minor timing/track differences, the models
forecast an associated attendant surface low to track NE along
the Srn New England coast Thu night, continue NE across the Gulf
of Maine Fri, then pass E of the NT1 waters Fri night. In regards
to the forecast gradients associated with this front, all of the
12Z models now forecast prefrontal Sly gale force boundary layer
(BL) winds to develop across the NT2 waters (primarily from the
gulf stream Swd) by late tonight and continue Thu/Thu night,
followed by postfrontal Wly gale force BL winds developing across
the central NT2 waters late Thu and persisting into Fri.
Therefore, continue to have relatively high forecast confidence
in the previously forecasted gale warnings associated with this
fropa. Overall, believe the 12Z GFS solution for this fropa looks
representative. Therefore for tonight through Fri night, will
populate 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 (primarily from the
gulf stream northward). So then will make some minor additional
edits to these winds primarily in deference to the 12Z ECMWF and
to maintain the forecast continuity of the associated gale
warnings.

In the long range, the 12Z global models agree that a more quiet
weather pattern will develop (with no associated warnings
required). Versus its previous respective runs, the 12Z GFS has
now trended slower with a warm front expected to move NE off the
mid Atlantic coast and into the central/Nrn NT2 waters Sat night
into Sun night, then continue into the NT1 waters Mon/Mon night.
The 12Z global GEM looks too amplified with the strong surface
low it forecasts to move off the mid Atlantic coast Sat night/Sun
and hence will be disregarded, while the 12Z UKMET does not look
progressive enough with the warm front. With the 12Z GFS
trending towards its slower solution, will favor the more
consistent 12Z ECMWF solution for the warm fropa and as a result
will transition to populating with 12Z ECMWF BL winds on Sat
through Sun night. Then on Mon/Mon night, the disparity between
the 12Z global models increases significantly. The 12Z GEFS Mean
indicates that the 12Z GFS solution then is too progressive.
Therefore, with not a particularly high level of forecast
confidence but since its supported by the 12Z UKMET, will
continue to favor the 12Z ECMWF solution of the warm front
stalling across the northern NT2 waters and a frontal wave
passing E along the front. Though based on the weak upper level
support forecasted, am concerned that the 12Z ECMWF is
overforecasting the strength of its frontal wave. So will
continue to populate with 12Z ECMWF BL winds on Mon/Mon night,
capped at 25 kt for now.

.Seas...A compromise between the slightly higher 12Z ECMWF
WAM versus the 12Z Wavewatch III initializes the current seas
best at the moment. With this in mind and with their associated
12Z GFS/ECMWF solutions being similar, will populate our forecast
wave grids with a 50/50 blend of the 12Z Wavewatch III and 12Z
ECMWF WAM seas for tonight through Fri night. Then since the 12Z
ECMWF solution will become favored, will transition to populating
with all 12Z ECMWF WAM seas on Sat through Mon night.

.Extratropical storm surge guidance...N/A.


.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Thursday into Friday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Thursday night into Friday.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale tonight into Thursday night.
.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 into Thursday night.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale tonight into Thursday night.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale tonight into Thursday night.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale tonight into Thursday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale tonight into Thursday.

$$

.Forecaster Achorn/Vukits. Ocean Prediction Center.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.