Marine Interpretation Message
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000
AGPN40 KWNM 220323
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
823 PM PDT Mon Aug 21 2017

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.

Synoptic systems affecting winds and seas over the forecast
waters will remain weak and winds will remain below gale force
threshold through the period. Satellite images show mostly cloudy
skies across the forecast waters with cyclonic circulation over
the south waters. Latest observations show higher winds to 25 kt
over the central waters. At 00Z the NCEP weather map has high
pressure 1026 MB near 35N140W with its ridge extending northeast
into the north waters. Low pressure 1014 MB centered over the
western edge of the southern waters. Pressure gradient is fairly
relaxed across the region and the models GFS/CMC/ECMWFHR/UKMETHR
support keeping a relaxed pressure gradient through most of the
forecast period. The models have initialized well the 00Z surface
observations with just minor differences that do not change the
main synoptic pattern. Will stay with GFS.

Seas are relatively higher over the southern waters with a peak
at 9 ft. Seas range between 3 and 6 ft over the northern and far
southeastern waters. NWW3 and ECMWFWAVE have both agreed well on
subsiding seas to below 8 ft across the region most of the
period.

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PREVIOUS DISCUSSION...

The 18z surface analysis indicated high pressure centered near
38N138W with ridge extending northeast into southern British
Columbia. Weak low perssure was just northwest of the southern
California waters. The most recent ascat pass from 1740z missed
most of the offshore waters, but did get a decent portion of the
coastal waters indicated the strongest winds around 25 KT over
the southern Oregon/northern California waters.

No big changes are anticipated for grids as the 12z models
continue to be in very good agreement during the period. At the
mid/upper levels, closed low off the southern California coast
will slowly shift east the next few days while weakening. At the
surface, the high pressure ridge will weaken the next few days
as a weak cold front approaches the Washington and Oregon
offshore waters later Tuesday, then passes southeast across the
waters Tuesday night and Wednesday. The front will then move into
the northern California waters Wednesday night before
dissipating over the central California waters Thursday. Winds
with this front will remain well below gale levels. Otherwise,
the coastal trough will reamain weak through midweek before
strengthening again later Thursday through Friday night, then
weakening again over the weekend. It appears now that any gales
later in the week will be confined to the far southern Oregon and
northern California coastal waters as all models indicate winds
below gale over the adjacent offshore waters. Will continue to
populate wind grids using the GFS 10m winds with very good
support from ECMWF/UKMET/CMC.

.SEAS...The 18z sea state analysis indicated that observed seas
were within a foot of the model guidance. Will continue to use
the WaveWatch III for wave grids through the period.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
     None.

.PZ6 California Waters...
     None.

$$

.Forecaster Musonda/Kosier. Ocean Prediction Center.



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