AGPN40 KWNM 251011
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
211 AM PST Sun Feb 25 2018

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

06Z NCEP surface analysis shows a cold front entering the PZ5
waters from the NW while a weak ridge extends SW from
southwestern Oregon. Surface observations and ASCAT show NW gales
behind the front and possible storm force NW Gulf of Alaska. To
the S the ridge extends into the central PZ6 waters from high
pressure centered well W of the area while a coastal trough has
re-formed along the central and southern Califormia coast, and is
pressing against the ridge more. A swath of NW winds 25 to 30 kt
has expanded along the California coast S of 40n and W of Channel
Islands in response, as indicated by 0435Z and 0530Z ASCAT
passes.

With the 00Z global models and NAM in agreement over most of the
period will populate the wind grids with the representative 00Z
GFS and taking into account unstable conditions especially behind
passing cold fronts, modified the GFS 10 meter winds using a
smart tool that places the higher first sigma level winds in
unstable areas and 10 meter winds in stable areas. This is done
through Tue. Result is not much change in warning headlines in
the near time as a period of gales are expected over parts of the
northern PZ5 waters today as low pressure over SE Alaska slides
into Western Canada with enhanced winds in the northwest flow in
the western semicircle of the low. Continue to anticipate gales
over parts of the northern and central PZ6 waters later Monday
into early Tuesday as low pressure strengthens over the southwest
U.S. while interacting with broad high pressure over the eastern
North Pacific. Toned down the stronger GFS by blending with 33
percent 00Z ECMWF. By Wed and into early Thu models are
indicating a significant upper trough digging S over or just west
of the northern offshore waters with models to varying degrees
developing low pressure over the PZ5 waters. Noting the
differences in the 00Z models, decided to use the 00Z CMC global
GEM for the winds from Tue night into early Thu as it appears to
be the best compromise in terms of location and intensity, and
maintains gales over parts of the PZ5 waters, strongest near the
low. Then later Thu and Thu night reverted back to the 00Z GFS
which is in line with WPC medium range guidance, calling for low
to stall over the PZ5 waters and to maintain continuity for now
made minor edits to keep northerly gales in the west semicircle
of the low just west of the waters.

.SEAS...Favored 00Z WW3 through Tue, then a 2:1 blend with the
00Z ECMWF WAM Tue night into Thu, and transitioning to an even
blend Thu and Thu night.

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

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
Gale today.
Gale Possible Wednesday into Wednesday night.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
Gale today.
Gale Possible Wednesday into Wednesday night.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
Gale Possible Wednesday into Wednesday night.
.PZZ905...Outer Waters from Cape Shoalwater to Cape Lookout...
Gale Possible Wednesday into Wednesday night.
.PZZ910...Outer Waters from Cape Lookout to Florence OR...
Gale Possible Wednesday into Wednesday night.
.PZZ915...Outer Waters from Florence OR to Point St. George...
Gale Possible Wednesday.

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
Gale Monday night.
.PZZ825...Inner Waters from Point Arena to Pigeon Point...
Gale Monday night.
Gale Possible Tuesday.
.PZZ830...Inner Waters from Pigeon Point to Point Piedras Blancas...
Gale Monday night.
Gale Possible Tuesday.
.PZZ930...Outer Waters from Pigeon Point to Point Piedras Blancas...
Gale Monday night.
Gale Possible Tuesday.
.PZZ835...Inner Waters from Point Piedras Blancas to Santa Cruz Island, CA...
Gale Monday night.
Gale Possible Tuesday.
.PZZ935...Outer Waters from Point Piedras Blancas to Santa Cruz Island, CA...
Gale Possible Tuesday.

$$

.Forecaster Bancroft. Ocean Prediction Center.