000
AGPN40 KWNM 180347
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
847 PM PDT Sun Jun 17 2018

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

High pressure will remain to the west of the region and maintain
a relaxed pressure gradient across the region through the
forecast period. GOES16 RGB Geocolor satellite images show mostly
patches of low warm clouds across the region. latest
scatterometer pass at 1913Z though missed the northern and
central region, it indicated winds less than gale force range
across the region. The latest NCEP map has weakened high pressure
1026 MB to the west of the northern waters. This high will
continue to weaken and have its center relocated just south of
30N and that will allow weaker frontal boundaries to move east
over the northern waters. Pressure gradient is quite relaxed
across the region and maximum winds will briefly remain at 30 kt
over the far northern waters.

Seas range between 7 and 10 ft across the region and both wave
models NWW3 and ECMWFWAVE fit well the observed seas pattern.
Both models have been quite consistent with the observations and
they agree well on keeping seas under 12 ft through the forecast
period. Will therefore just continue with ENP for seas.

At 500 MB, an upper level ridge now dominates the waters as most
of the energy is now just east of the region and that has
allowed a relaxed pressure gradient over the forecast waters
including the central region. Models indicate that the upper
level ridge will weaken and allow two areas of energy from the
south and north to slowly merge and move slightly east.
Meanwhile, the upper level high pressure ridge will persist over
the eastern portion of the southern waters and that will force
the energy to move northeast and will not impact the waters.
Toward the end of the forecast period, high pressure will weaken
inland and allow some energy to drop down over northern
California and that will affect the gradient over the central
waters and elevate winds over the eastern portion and gales are
possible Friday but will keep winds less than gale force for
now.

Models GFS/CMC/UKMETHR/ECMWFHR have initialized well the latest
synoptic surface observations especially across the forecast
waters. The models agree well on keeping weakening high pressure
to the west. Some differences are only in the extended period
when winds ware expected to be elevated. For now will just stay
with GFS.

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PREVIOUS DISCUSSION...

12z global models in good agreement through the forecast period.
For the wind grids, will lean towards the 12z GFS through the
period, as it has good support from both the ECMWF and the UKMET.

Trough along Vancouver Island expected to persist tonight. Latest
model guidance showing any gales associated with this system will
be north of the forecast waters, with winds to 30 kt possible in
the northern portions of the Washington offshore waters. Trough
begins to weaken Mon and Mon night, with conditions improving.

Trough along California is expected to continue to weaken
tonight. Winds to 25 kt off northern California currently are
expected to become light by Mon, with generally quiet conditions
expected elsewhere across the California offshore waters. Trough
begins to slowly strengthen later this week, with winds possibly
approaching gale force by the end of the forecast period. Global
models keeping winds just below gale force at this time, and will
keep winds to 30 kt for this package.

.SEAS...Wave guidance within a foot or two of current
observations. 18z sea surface analysis showing max of 11 ft off
the northern and central California coast, with another max of
11 ft off Vancouver Island in association with the coastal trough
there. For the wave grids, will lean towards 12z ENP values
through the forecast period.


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



.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
None.

.PZ6 California Waters...
None.

$$

.Forecaster Musonda/Achorn. Ocean Prediction Center.