000
AGPN40 KWNM 230326
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
726 PM PST Wed Jan 22 2020

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

At 03Z this evening, a triple point is near 53N 132w, trailing
ahead of a low pressure system. The associated southern
attendant cold front from the triple point is now moving towards
the Outermost PZ5 and northern Outermost waters of PZ6. As this
parent system cycles more northwards overnight towards the
extreme SE AK Coast, it will pull the cold front across these
waters. The strongest subgale south southwesterlies will taper
down by Thur afternoon from west to east, with the best chance of
short gales still remaining in the immediate waters off of the
WAA/OR coastal mountains as the front pulls ashore. Only a weak
impulse upstream is progged across the waters for Thu night, with
another 993-995 low development during Fri afternoon, which will
pull another warm front across Fri night with stronger subgale
winds across all PZ5 and Northern PZ6 Regional Pacific waters.
Across the Central and Southern PZ6 waters, high pressure will
keep improved winds and seas in place through this short term.
Bottom line is no warning expected for the next 4 periods on this
update cycle. As such, no change will be made to the grids on
this cycle.

.Seas...the 00Z sea state analyisis properly depicted the
elevated seas off of Southern WA and all of the OR coasts. As
such no changes will be made to the short term forecast attm.

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PREVIOUS DISCUSSION...

18Z NCEP surface analysis shows a warm front SE across the
Washington waters while a cold front trails S from a new triple
point low center 50N 140W 987 mb. A high pressure ridge
associated with a 1026 mb high 31N 126W remains over the central
and southern California waters. An 1816Z ASCAT-A pass and a ship
report near the central Oregon coast show southerly gales along
the central and southern Oregon coast to the Point St. George
area, and buoys to the N show SE gales W and NW of Vancouver
Island. ASCAT data and surface observations show winds 20 to 25
kt elsewhere N of 40N and 10 to 20 kt elsewhere, highest near
the Channel Islands. At this time, as was the case yesterday,
models keep the winds ahead of the cold front less than gale
force except possibly near the Oregon coast and along the
Canadian coast tonight into Thu. The low pressure will track N
into the Gulf of Alaska with the cold front expected to slow and
weaken across the northern PZ6 waters later Thu and Thu night.

Then another weaker 992 mb system is progged to develop after
18Z Fri and track toward the Queen Charlotte Islands and brush
the NW PZ5 waters Fri night and early Sat. The ECMWF, CMC global
GEM and GFS develop gales over or near the NW waters with the
GFS strongest and UKMET faster and weaker. This system has a
negative tilt shortwave trough associated with it with the
weaker UKMET discounted. The low will lift N and push a cold
front through the waters with the front stalling across the
northern PZ6 waters by early Sat. The afternoon package will be
based on the representative 12Z GFS through 18Z Fri and an even
blend of the 12Z GFS and ECMWF through 12Z Sun. A new wrinkle to
this forecast is a southern stream H5 shortwave developing
negative tilt and developing a low on the front which moves
north-northeast near the coast and inland over NW Washington or
southern British Columbia with the blended GFS/ECMWF used. This
has the potential to develop gales in the offshore waters but
since this is a new development the blend limits any gales to
the coastal waters. Another low follows, approaching the
northern Waters Sun and weakening to a trough over the northern
waters by early Mon with another weakening system following Mon
night. Beyond Mon night have low confidence in the forecast, as
the 12z models show considerable spread in the track and
intensity of a stronger low coming out of the North Pacific
toward the Gulf of Alaska. The grids after 12z Sun through Sun
night are based on a blend of the 12Z UKMET and 12Z GFS
transitioning to the 12z CMC global GEM Mon and Mon night and
then blended the previous grids with the 12z GFS.

Marine conditions across PZ6 continue to remain uneventful and
well below any warning criteria, as a persistent near 1025 mb
surface ridge continues to influence the marine conditions
across these waters for tonight through much of the period.
Confidence in the forecast is about average for the more active
weather in the north, becoming below average later in the
weekend and early next week.

Seas...Will continue with a 50/50 blend of the ENP Wavewatch and
ECMWF WAM thru Mon night, then old grids blended with the 12Z
ENP thereafter.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
None.

.PZ6 California Waters...
None.

$$

.Forecaster Futterman/Bancroft. Ocean Prediction Center.