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AGPN40 KWNM 290908

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
208 AM PDT Mon May 29 2017

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

The 06Z NCEP surface analysis shows a low pres trough over the
western CONUS, with a high pres ridge over the offshore waters.
The trough is expected to persist near the California coast
through the period. A weak cold front will move east over the
washington and oregon offshore waters Wednesday and Wednesday
night, followed by another weak cold front late Thu into early
Fri. Otherwise, the ridge will prevail over the offshore waters
through Tuesday then weaken Tuesday night into Thursday night
with the passage of the weak fronts through the northern waters
which will weaken the ridge. Then as the associated low pressure
system passing NW of the waters lifts toward the NW Friday and
Friday night the ridge will build back northward over the waters.
approach and during the forecast period. Latest available high
resolution ASCAT-B shows more widespread NW winds of 20 kt over
the PZ6 waters south of Cape Mendocino with areas of 25 kt in the
adjacent coastal waters, and light winds in the 5 to 15 kt range
within the ridge over the PZ5 and NW PZ6 waters.

Models...The 00Z global models and 00Z NAM are in very good
overall agreement across the offshore waters today into Thursday
night. The consensus of the models shows winds to 25 kt in NW
flow over the coastal and inner offshore zones of the central
california waters and south to the vicinity of the Channel
Islands today into Tue night, followed by a temporary shift south
of the strongest winds Tuesday night into Thursday night with the
weakening of the ridge noted above. Versus their respective
previous runs, the 00Z ECMWF has trended toward the GFS solution
building more of a ridge over the PZ5 waters Friday and Friday
night while the 00Z GEM trended toward the old ECMWF and showing
a low near the Washington waters and therefore looks like an
outlier. The model consensus is to rebuild the eastern Pacific
ridge across the PZ5 waters. For the new forecast will use the
representative 00Z GFS 10m solution for the wind grids over the
entire forecast period. Late Friday and beyond the trend is for
expansion and some shift northward of the strongest winds (around
25 kt) into the far SE PZ5 waters, and it appears further
increases in winds are likely beyond day 5.

Seas...The 00Z ENP version of the Wavewatch III and 00Z ECMWF WAM
both initialized reasonably well over the offshore waters versus
available observations and altimeter passes. The models are in
good overall agreement through Thu night, with only minor
differences noted, so will use a 50/50 blend of the 00Z
Wavewatch/00Z ECMWF WAM through Thu night in order to smooth out
the model differences. Then with more divergence of the models
will use a 2/3 00Z ECMWF WAM/ 1/3 00Z NWW3 blend with this blend
favoring the higher seas in the ECMWF WAM versus the NWW3 developing
off California in response to the increase in northerly flow
Friday and Friday night.

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


.PZ5 Washington/Oregon Waters...

.PZ6 California Waters...


.Forecaster Bancroft. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.