Marine Interpretation Message
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000
AGNT40 KWNM 191237
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
837 AM EDT Tue Jun 19 2018

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

Current Conditions...The 06z ncep surface analysis shows a 993 mb
low over the western Gulf of Saint Lawrence, with an associated
cold front extending SW from the low and across the Maine coast
into New York state. The analysis also indicates a low pressure
trough over the mid Atlantic states and the Carolinas, with a
high pressure ridge across the southern nt2 waters. Latest
available ascat and ascat hi-res passes from last night show 15
to 25 kt winds over the nt1 and northern nt2 waters S and E of
1000 fathoms, with 10 to 20 kt winds indicated over the remaining
offshore waters. Lightning density product data at 11z shows
scattered showers and tstms over zone 915 in the northern nt2
waters, with isolated showers and tstms across the outer zones of
the central and southern nt2 waters.

Models/Forecast...The 00z medium range models are in good
agreement across the offshore waters over the entire forecast
period, with the 00z ecmwf/gfs showing the best agreement. Will
use the 00z ecmwf for the wind grids during the forecast period,
mainly to maintain forecast continuity but also because the ecmwf
looks very representative of the consensus of the models. All of
the medium range models indicate that winds will remain below
gale force through at least Sat night, so confidence is very good
for no hazard grids during the forecast period. Am not planning
to make any significant changes to the current forecast trend at
this time.

Seas...The 00z wna wavewatch and 00z ecmwf wam both initialized
well over the coastal and offshore waters, and are in good
overall agreement through the forecast period. Will use a 2:1
blend of the 00z ecmwf wam/wna wavewatch for the sea height grids
during the forecast period, in order to enact a comprimise
solution while also ensuring continuity with the preferred 00z
ecmwf wind grids.

Extratropical Storm Surge Guidance...N/A.

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

The Ascat wind retrievals from 02Z late last night indicated
moderately strong SW flow ahead of a cold front over New England,
with winds up to 30 kt in the Gulf of Maine. 00Z ECMWF winds are
initialized well when compared with the data, while the 00Z GFS
was initialized low. Current surface observations along the
coast of Maine show winds down to about 25 kt at a couple of
elevated C-MAN stations at 06Z, while the remainder of the
observations show no more than 20 kt. The 00Z ECMWF is in good
agreement with the 00Z GFS on the timing of the front as it moves
through NT1 and NT2 today into Wed, before stalling across
central NT2 late Wed. The 00Z models all maintain winds below 34
kt in the short range, and confidence is high with winds
remaining below gale force as a result of the good agreement.
As a result, am planning on maintaining no warning headlines, and
will start out with the 00Z ECMWF since it is initialized the
best and seems representative when compared with the rest of the
00Z models.

The 00Z GFS and ECMWF then remain in good agreement through the
medium range period, and indicate the front will continue over
NT2 as a weak low moves E off the Delmarva peninsula Thu and
passes E across the NT2 offshore waters along the front Thu night.
There are some slight differences on the timing and location of
the low and front, but overall the models agree well on the
timing. The ECMWF then indicates the front returning N as a warm
front Fri into Sat, and again differences are slight between the
00Z ECMWF and GFS. As a result of the good overall agreement, am
planning on staying near the 00Z ECMWF through the remainder of
the forecast period, mainly to stay near continuity since the
previous forecast stayed close to the ECMWF.

.SEAS...Both the 00Z Wavewatch and ECMWF WAM have initialized
well when compared with the 06Z sea state analysis and
observations in the W Atlc. The models generally agree well
through the forecast period, so planning on using a 2:1 blend of
the 00Z ECMWF WAM and Wavewatch as a compromise to the small
differences while placing a higher emphasis on the ECMWF WAM to
account for the preferred 00Z ECMWF winds.

.EXTRATROPICAL STORM SURGE GUIDANCE...No significant positive
surge events are expected during the next several days.

.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
     None.

$$

.Forecaster Scovil/Kells. Ocean Prediction Center.



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