000
AGPN40 KWNM 222026
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
126 PM PDT Wed Mar 22 2017

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

Grids: 12z GFS into Sat night, then a transition to the 12z
ECMWF thereafter. Discussion follows.

Active weather in store across the E Pacific over the next
several days. Beneath progressive flow aloft, several lows,
fronts, and troughs will impact the offshore zones.

Tonight into Thu night: strong NW flow forecast to increase
tonight across the far inner / srn CA offshore zones. Will
continue to lean more towards regional and global consensus; that
is will use the 25-30 kt maxes from the 4km NAM and 18z HRRR,
with continued support from the UKMET, ECMWF and GFS. Would not
be surprised to see gusts to gale force, but these will likely be
confined to the coastal zones in the waters near the Channel
Islands. Otherwise, a strong cold front will move across the
EPAC Thu and Thu night, bringing gales across most zones north of
about 40n. Timing (onset around 15z Thu in outer waters) and
strength of pre-front winds have been remarkably consistent over
the past several days, and accordingly warning confidence remains
well above average.

Sun and Sun night: forecast becomes more problematic as another
strong cold front swings across the northern waters Sun and Sun
night. GFS has again trended slower with the passing boundary,
about 6 hours behind non-NCEP consensus. And similar to its 06z
cycle, it remains a significant and glaring outlier developing a
strong triple point low over the WA/OR waters, then stalling the
feature off the coast through Mon night. Deference to the ECMWF
will keep forecast continuity, but with confidence lacking during
this time frame, will continue to keep winds to 30 kt and below
gale warning criteria. Worth mentioning that all guidance does
suggest minimal pre-front gales -- but as of right now, not
being able to confidently pin down timing and location, seems a
little feckless to add warning headlines at this time with any
degree of confidence.

Mon and Mon night: models forecast forming low over the interior
Great Basin, while strong high pressure builds east towards the
offshores. Forecast gradient will be strong enough to generate
widespread 25 kt winds across most of the offshore waters south
of about San Francisco Bay. Again, will use the ECMWF for timing
and extent of associated winds, and will limit max values to 25
knots being so far in the extended portion of the forecast.
Assuming models remain consistent, these values will likely
increase as the event draws nearer.

Seas: in similar fashion to the wind grids, will use the WW3 ENP
into Sat night, then transition towards the ECMWF WAM thereafter.
Will trim back values slightly (2-3 ft) over the southern CA
waters Mon and Mon night, where the ECMWF hints at possible gales
in the strong prevailing n to nw flow.

Extratropical Storm Surge Guidance: n/a


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
Gale Thursday into Thursday night.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
Gale Thursday.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
Gale Thursday into Thursday night.
.PZZ905...Outer Waters from Cape Shoalwater to Cape Lookout...
Gale Thursday.
.PZZ810...Inner Waters from Cape Lookout to Florence OR...
Gale Thursday into Thursday night.
.PZZ910...Outer Waters from Cape Lookout to Florence OR...
Gale Thursday.
.PZZ815...Inner Waters from Florence OR to Point St. George...
Gale Thursday into Thursday night.
.PZZ915...Outer Waters from Florence OR to Point St. George...
Gale Thursday.

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

$$

.Forecaster Collins. Ocean Prediction Center.