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187
AGNT40 KWNM 242021
MIMATN

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
300 PM EST TUE 24 JAN 2017

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

The most recent Ascat data over the west Atlantic missed the
Gulf of Maine where the highest offshore winds were occurring
this morning. However, a 1350Z overpass did indicate east winds
to 45 kt just east of this area. At 18Z the occluded front
extended east northeast from near Cape Cod Bay across the Gulf
of Maine with the strongest winds just poleward of the front.
Based on the latest buoy observations and high resolution
guidance, will likely downgrade the storm warning to gale across
the Gulf of Maine with the 4PM EST NT1 issuance. Storm force
gusts are likely through through most of the evening, and could
not rule out some localized sustained storm force winds off
western Nova Scotia and the Bay of Fundy as winds channel along
the coast. For the near term winds grids through 06Z/25, blended
the higher 12Z NAM 0-30mb agl winds with the 12Z ECMWF.

As the associated negatively tilted upper level trough lifts
northeast toward the Canadian Maritimes over the next 48 hours,
upper heights will build across the offshore waters. The 12Z
models are in excellent agreement that fairly widespread
northwest gales will impact the offshore waters tonight through
Wednesday in the moderate cold air advection. There should be a
lull between gale events Wednesday night as the 12Z models are
consistent with a cold front moving offshore Thursday with winds
again increasing to gales at that time. Have high confidence
with these gales given the above average model agreement. Models
agree that a mean upper level trough will persist across the
eastern seaboard with a polar airmass predominating through the
weekend and strong to gale force west to northwest offshore
winds. Model disrepancy increases late in the weekend as the 12Z
GFS becomes more amplified and less progressive than the 12Z
ECMWF with the upper shortwave at the base of a long wave trough
across the southeastern US. The 12Z UKMET shares a similar
timing with the 12Z ECMWF, but is more amplified than the ECMWF.
As a result the ECMWF is again indicating gales across the mid
Atlantic waters Sunday into Sunday night. Will be using an even
blend of the 12Z GFS and 12Z ECMWF at that time and limit winds
to 25 or 30 kt, as do not have forecast confidence in either
deterministic solution.

Although the 12Z ECMWF WAM is much higher than the 12Z Wavewatch
III across the Gulf of Maine, even it is about 6 to 8 ft too low
along the Maine coast where buoy 44030 had a 27 ft report at
18Z. For the near term wave height grids, used the 12Z ECMWF WAM
and adjusted it upward by 20 percent across the Gulf of Maine.
Thereafter used a 3:1 ECMWF WAM to WW3 blend through the
forecast period, as preference continues with the higher ECMWF
WAM guidance.

Extratropical Storm Surge Guidance: Water levels across Long
Island Sound are running 1 to 1.5 ft higher than the latest
ESTOFS surge guidance this afternoon. As the strongest easterly
winds continue to move northward, the 12Z ETSS and 12Z ESTOFS
seem to capture the diminishing surge reasonably.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Clark. Ocean Prediction Center.



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