Marine Interpretation Message
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000
AGPN40 KWNM 240240
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
740 PM PDT Tue May 23 2017

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

The most recent ASCAT pass from 18Z indicates winds 15-25 kt
across the PZ5 and northern California waters. The pressure
gradient along the northern California coast is expected to
strengthen overnight and produce gales. The gale conditions are
expected to persist for 24-36 across across the region before
dimiinishing as the gradient weakens. I dont plan on making any
changes to the current grids or associated text forecast.

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PREVIOUS DISCUSSION...

Gale warnings in the short term over the central waters will be
retained then a high pressure ridge will dominate the forecast
region in the extended period. Geocolor satellite images still
show anticyclonic circulation center west of the north California
waters. The latest observations including scatterometer pass
about show maximum winds over the central waters nearing gale
force. At 1800Z, the NCEP surface map has an inland trough near
the coasts from California to Washington states. Weakening high
pressure 1028 mb west of the region near 40N140W is part of a
broad high pressure with center 1037 Mb over the central Pacific
near 40N160W, that extends a ridge northeast into the north
waters and southeast into the southern waters. A cold front is
over the Washington waters. Pressure gradient tightened over the
central waters.

The models CMC/GFS/UKMETHR/ECMWFHR have initialized well the 18Z
surface observations with just small differences on the position
of the weak high pressure west of the region. UKMETHR and GFS
suggest high pressure center while ECMWF and CMC have just a
ridge in the same area. These small differences do not project
differences in the synoptic pattern over the waters and so will
continue with GFS for winds. In the short term the models agree
on dissipating the high pressure west of the region.

.SEAS...Seas range between 4 and 6 ft over the southern waters
while they range between 6 and 8 ft over the central and northern
waters. NWW3 and ECMWFWAVE fit well the 18Z observed seas pattern
and both wave models have been quite consistent with the observed
seas pattern though NWW3 was a foot lower in areas with higher
winds. Will not make major changes to the previous forecast and
will continue with ECMWFWAVE guidance for seas.


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


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
     Gale Wednesday into Wednesday night.
.PZZ815...Inner Waters from Florence OR to Point St. George...
     Gale tonight into Wednesday night.

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
     Gale tonight into Thursday.
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Wednesday into Wednesday night.

$$

.Forecaster Shaw/Musonda. Ocean Prediction Center.


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