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333
AGNT40 KWNM 250216
MIMATN

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
1015 PM EDT FRI 24 MAR 2017

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

The ship which reported 30 kt south of Block Island at 00Z has a
mean wind speed error of +11 kt. After taking this error into
consideration and as suggested by the surrouding buoy
observations, southwest 20 to 25 kt appears more representative
of the present conditions. The 18Z NAM/GFS/GEFS were generally
consistent with their respective previous runs and overall the
guidance is in above average agreement across the west Atlantic
for the next several days. The cold front will move off the New
England coast tonight, continue to drop south across the waters
Saturday and Saturday night, and stall off the Delmarva coast
early Sunday. The previous OPC wind and wave height grids look
reasonable and will not be making any significant changes in
this evenings forecast updates. Wave heights across the Gulf of
Maine are already up to 8 to 9 ft this evening. We adjusted the
previous wave height grids upward by a ft or so across the NT1
waters for the near term to better match the current buoy
observations.

----------------------------------------------------------------
...Previous Discussion...

There was an ASCAT pass at 14Z with a swath across the wrn areas
of the mid Atlantic into the New England waters. Winds were to
20 kt over the wrn sections of the nrn Mid Atlantic into the New
England waters which was close to the 15Z GFS winds over this
region. At 17Z buoy observations close to the ME coast had winds
to 30 kt.

At 18Z strong high pressure was situated over the ern areas of
the central Mid Atlantic waters. The high pressure area moves S
through tonight while becoming weaker. A warm front should move
NE over the nrn New England waters later this afternoon into
early tonight...then briefly stall as low pres develops and
moves E along the frontal boundary. Models show developing low
pressure moving along the frontal boundary and E of the New
England waters later tonight while strengthening. The GFS is a
bit stronger with winds than other guidance with winds near Gale
force just E of the waters. Will keep max winds to 30 kt over
the New England and nrn Mid Atlantic waters. Associated cold
front moves S across the New England waters later tonight and
Saturday...then crosses into the nrn Mid Atlantic by late
Saturday afternoon/early Saturday night into Sunday...then
stalling along and E of the Delmarva coast before returning to
the N as a warm Front Sunday night. Some models such as the
GEM/GFS/ECMWF do show low pressure moving E along the front over
the New England waters Monday and Monday night. The GFS/GEM
models seem too strong with the winds N of the low and prefer
the weaker winds with ECMWF. By Tuesday and Tuesday night model
guidance is not in good agreement. The 12Z UKMET/ECMWF are much
weaker than the GFS with low pressure that moves off the NJ
coast and strengthens into Wednesday and Wednesday night. Prefer
the GFS which seems more likely to be correct considering the
strong upper shortwave that moves offshore into the New England
waters Wednesday night. Will go no stronger than 30 kt due to
the disagreement among the models.

Seas...At 18Z the multigrid WWIII and ECMWF wam were in close
agreement with observed seas across the offshore waters. Will
use a 50/50 blend of the WWIII and ECMWF wam through Tuesday
morning...then favor the WWIII for the remainder of the forecast
period.

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

.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
     None.

$$

.Forecaster Clark/Rowland. Ocean Prediction Center.



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