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000
AGNT40 KWNM 060132
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
832 PM EST MON DEC 5 2016

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

The 00z surface analysis indicate low pressure over the northern
NT2 waters near 37N70W with a cold front trailing southwest to the
eastern Cape Fear waters. This front is well depicted by satellite
imagery and lightning detection with scattered thunderstorms noted
over the far southeast Cape Fear waters. The 18z GFS and NAM
indicated no major changes from the previous 12z runs, and both
continue to be in decent agreement with the previous 12z runs at
least during the short term period. The gales for tonight over the
northeast portion of the NT2 waters still looks good as do expect
enhancement over the Gulf Stream portions. The 18z GFS/NAM are
also similar with the next strong low to move off the southeast
coast Tuesday afternoon then tracking east across the central NT2
waters Tuesday night and Wednesday. Then looking ahead to later in
the week the models continue to trend closer with the timing of
strong cold front, although are weaker with the post frontal
winds. The 18z GFS 30M winds still indicating fairly large area of
post frontal gales which is likely more representative given the
strong cold air advection. In summary, do not on making any major
changes to existing grids for the evening update. The 00z sea
state analysis indicated that the ECMWF WAM seems to be more
representative of observed seas.

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PREVIOUS DISCUSSION...

The 1430Z and 1520Z Ascat overpasses confirmed the gales east of
the surface low and associated cold front extending along a line
from near 36N73W southwest to 33N77W. These Ascat winds across
the Gulf Stream were generally higher than most 12Z models
initialized. The exceptions were the HRRR and 4km NAM. The
previous OPC wind grids were also in reasonable agreement with
the Ascat. Updated the near term grids with the 12Z ECMWF and
like was done previously adjusted the higher winds near the low
center and front up by about 10%. The 12Z models are in good
agreement that another developing surface low will move off the
Georgia and South Carolina coast late tonight into early Tuesday
morning. The 12Z model solutions diverge early Wednesday and
Wednesday night as to how quickly the low will eject
northeastward away from the NT2 waters. Versus its previous run
the 12Z ECMWF is even slower. The 12Z GFS offers a compromise
between the faster UKMET and slower ECMWF...and is well
supported by the 00Z ECMWF. However do prefer the stronger ECMWF
winds. The previous OPC wind grids which were based on the 00Z
ECMWF look reasonable as they reflect a similar timing to the
12Z GFS yet still depict fairly widespread gales.

Models have then come into good agreement with the timing of an
arctic cold front reaching the New England and Mid Atlantic
coasts late Wednesday night and Thursday. Over the last day or
so the guidance has generally trended weaker with the upper
level trough late this week and are not as enthusiastic with the
height falls. Consequently models are also weaker with the post
frontal northwest winds Thursday night through Friday night. At
that time adjusted previous wind grids down slightly to account
for this trend but grids are still higher than the 12Z guidance.
Offshore winds should then diminish Saturday and Saturday night
as strong high pressure reaches the mid Atlantic coast.

.Seas...There has not been a recent altimeter pass across the
NT2 waters so it is difficult to assess how well the models are
intialized this afternoon. Based on earlier buoy reports when
the front was closer to the coast...am inclined to favor the
higher 12Z ECMWF WAM for the near term. Then with favoring the
previous official wind grids beginning Tuesday will also be
retaining the previous wave height grids through Saturday night.

.Extratropical Storm Surge Guidance...N/A.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Kosier/Clark. Ocean Prediction Center.


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