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000
AGPN40 KWNM 231501
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
701 AM PST Fri Feb 23 2018

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

12Z surface analysis indicates a cold front approaching the NW
waters that will move through the waters today and tonight,
bringing in some gales to the northern waters.

Still expecting a similar pattern to continue with a high
pressure ridge to the west of the and a series of shortwaves
moving SE across the northern and central waters. Model agreement
continues through Monday night then begin to diverge Tuesday,
revealing some pretty significant differences by Tuesday night.
That being said, have no new reasons to disagree with the
previous forecast, so will continue the current forecast with
some edits. Will revisit the later periods as the new model
solutions become available.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

0435 ASCAT-B overpass shows gales near the central California
coast near Point Reyes but otherwise a swath of 30 kt from Cape
Blanco to Monterey Bay and another area of 30 kt near the Channel
Islands. With negative static stabilities still prevailing over
much of the area in the wake of the latest upper shortwave
passage, now inland, for initial wind grids used the higher first
sigma level winds off the 00Z GFS with some minor edits to
approximate initial surface observations and ASCAT. As was the
case in the current forecast, am not carrying any gales in the
offshore waters to start the forecast. Awaiting arrival of the
next in a series of shortwaves and cold fronts.

The weather pattern in the NE Pacific has been and remains fairly
consistent with a high pressure sure ridge to the west of the
waters and a series of short waves moving over the ridge and SE
across the northern and central waters. The 00Z Global models and
NAM are all in very good agreement into early Mon but then begin
to show some subtle differences into Tue and then increasing
differences Tue night. Will continue the use of the 00Z GFS 10
meter winds modified using a 10m/30m stability tool which gives
the higher first sigma level winds in the cold surges
accompanying the shortwave and cold frontal passages. This will
help keep gales over the waters with the associated fronts,
mainly affecting the PZ5 waters through Sun with above average
confidence. Later Mon into Tue the GFS and ECMWF show gales off
of central California with ECMWF strongest, even in their 10
meter winds. However the 00Z CMC global GEM and UKMET show no
gales. During the later Mon and Mon night time frame used a 50/50
blend of the 00Z GFS 10m/30m winds with the 00Z UKMET resulting
in small area of marginal gale Mon night into Tue portions of central
California inner waters, and then Tue and Tue night used a 50/50
blend of the 00Z GFS/ECMWF which are in very good agreement with
a few intensity/wind direction differences, and both have been
more consistent later in the forecast, when CMS GEM and UKMET
diverge to different solutions.

.SEAS...Will use the higher values of the 00Z ECMWF WAM for today
into tonight which initialize better but otherwise into early Mon
use the 00Z WW3 with some edits during the time periods of gale
force winds in the wind grids. Then later Mon to Tue night used
an even blend of the two models.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
     Gale tonight into Saturday night.
     Gale Possible Sunday.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
     Gale tonight into Saturday night.
     Gale Possible Sunday.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
     Gale Saturday.
     Gale Possible Sunday.
.PZZ905...Outer Waters from Cape Shoalwater to Cape Lookout...
     Gale Saturday.
     Gale Possible Sunday.

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

$$

.Forecaster Sommerville/Bancroft. Ocean Prediction Center.



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