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 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
AGNT40 KWNM 110750
MIMATN

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
250 AM EST MON 11 DEC 2017

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

The highest Ascat wind retrievals from last evening were to 25
kt across the NT1 and northern NT2 zones. The 00Z models were
all slightly weaker than this Ascat data. The previous OPC wind
grids which blended the higher GFS first sigma level winds with
the ECMWF 10m winds appeared well initialized.  The most recent
GOES water vapor imagery clearly depicts the first few upper
level features forecast to impact the offshore waters over the
next few days. The first upper level shortwave trough is moving
E across the Ohio Valley and the 00Z models are consistent that
this feature will exit the northern Mid Atlantic and New England
coasts later this morning into early this afternoon and support
a developing cold front across the offshore waters. As a weak
surface low passes just N of the NT1 waters and pulls the cold
front across the area, the guidance is consistent that will see
some enhancement in the surface winds, only to 25 kt or so,
today. A weak high pressure ridge should then rapidly pass E
across the waters tonight. Based on its superior initialization,
will update the today/tonight wind grids with the same even
blend of the 00Z GFS first sigma level and 00Z ECMWF 10m winds.


The next more vigorous upper level feature is dropping SE across
the Northern Plains this morning and is expected to approach the
Mid Atlantic coast Tue while weakening. Another sharply
amplified upper shortwave trough should then quickly follow
later Tue/Tue night with the resultant upper low becoming
negatively tilted off the northern Mid Atlantic and New England
early Wed. The 00Z models have converged with the track and
timing of intensifying surface moving northward through New
England and Quebec late Tue through Wed night. Gale headlines
will remain in the forecast for southerly winds ahead of the
cold front beginning Tue. Then by Tue night and extending into
Thu, the 00Z models are consistent that the gales will become
widespread across the offshore waters in some of the strongest
cold air advection of the season so far. We have well above
average forecast confidence with these gales. Will be
maintaining continuity with the wind grids and using the same
even blend of the ECMWF 10m and GFS first sigma level winds
through Thu. Guidance is then rapidly moving a clipper type low
off the Mid Atlantic coast Thu and suggesting another round of
potential gales across the NT2 waters. Both the 00Z ECMWF and
00Z UKMET are faster than the 00Z GFS. With the lack of ensemble
consensus with this system, will hold off on adding any gales to
the forecast at this time. However we do favor the more
progressive ECMWF/UKMET.

The discrepancy between the models then increases significantly
with yet another amplified upper level trough forecast to
approach the coast Fri and move offshore Fri night. The GFS has
consistently been the more amplified outlier, and the 00Z GFS
even trended slightly stronger from its previous run. With
forecast uncertainty higher than normal at days 4/5 and to
maintain continuity, we will be opting to populate our wind
grids with the WPC medium range guidance, which does increase
winds to 30 kt across the NT2 waters Fri and Fri night.

Seas...Both the 00Z Wavewatch III and 00Z ECMWF WAM initialized
well over the offshore waters, and intend to use a 1:1 blend
through Thu night, before transitioning solely to the 00Z ECMWF
WAM Fri.

Extratropical Storm Surge Guidance: No major deviation from the
latest guidance appears needed at this time, with little chance
for a significant positive surge event along the East coast over
the next few days.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Tuesday night.
     Gale Possible Wednesday into Thursday.
.ANZ805...Georges Bank west of 68W...
     Gale Possible Wednesday into Thursday.
.ANZ900...Georges Bank east of 68W...
     Gale Tuesday night.
     Gale Possible Wednesday into Thursday.
.ANZ810...South of New England...
     Gale Tuesday night.
     Gale Possible Wednesday into Wednesday night.
.ANZ815...South of Long Island...
     Gale Tuesday night.
     Gale Possible Wednesday into Wednesday night.

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Gale Tuesday night.
     Gale Possible Wednesday into Wednesday night.
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Tuesday night.
     Gale Possible Wednesday into Wednesday night.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday into Wednesday night.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Tuesday night.
     Gale Possible Wednesday into Thursday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday into Thursday.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles
Light...
     Gale Tuesday night.
     Gale Possible Wednesday.
.ANZ828...Inner Waters from Cape Charles Light to Currituck
Beach Light...
     Gale Tuesday night.
     Gale Possible Wednesday.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras
Canyon...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday into Wednesday night.
.ANZ830...Inner Waters from Currituck Beach Light to Cape
Hatteras...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale Tuesday into Tuesday night.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale Tuesday into Tuesday night.
     Gale Possible Wednesday.

$$

.Forecaster Clark. 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.