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000
AGNT40 KWNM 212016
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
416 PM EDT Mon Aug 21 2017

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

At 18z a stationary front was located over the southern NT2
waters. A 1025 mb high was located over the northern NT2 waters
with its ridging extending into the NT1 waters with a 1023 mb
high just east of the southern waters with its ridge extending
into that region. Latest ASCAT high resolution data revealed 5-15
kt winds across both the NT1 and NT2 waters which matched well
with values in the ongoing forecast for the today period heading
into tonight.

12z guidance was in good agreement over the offshore waters
through roughly late Thursday into Friday with differences noted
by Saturday, again in regards to possible tropical activity
moving into the southern NT2 waters at that time. As a result
favored 50/50 blend of the 12z GFS/ECMWF winds over the period.
Stationary front weakens over the southern NT2 waters tonight
into tomorrow with high pressure ridging expanding to cover the
entire region. Guidance continues to remain in good agreement
concerning the next cold front expected to move east across the
waters with frontal passage expected late Tuesday night into
Thursday night across the NT1 waters with the southern end of the
front hanging back over the NT2 waters into at least early
Saturday. Anticipate strongest winds ahead of the front to be
over the over the NT1 and northern NT2 waters but with southerly
flow thinking winds maxing out around 25 kt is reasonable.

Regarding the guidance in reference to any possible tropical features,
right now guidance is in agreement in developing something off
of eastern FL with it moving towards or possibly just into the
far southern NT2 waters at the end of the period. The 12z
GFS/ECMWF/UKMET/CMC all hold this feature just south of the
southern NT2 waters through Saturday though impacts from the
northern quadrant or semicircle of the feature may impact the
water. In the case of the UKMET/CMC this solution is slower as
compared to yesterday`s 12z runs. With that noted in terms of the
latest model trend heading into the weekend, forecast won`t
mention hint of any possible tropical development for now and
will show the southern end of the front just clearing the
southern waters per using a 50/50 blend of the 12z GFS/ECMWF.

.SEAS...Favored 12z NWW3/ECMWF WAM guidance over the 5 day period
given choice to use 50/50 blend of the 12z GFS/ECMWF winds.


.EXTRATROPICAL STORM SURGE GUIDANCE...n/a.


.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
     None.

$$

.Forecaster Holley. Ocean Prediction Center.


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