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AGPN40 KWNM 202208

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
308 PM PDT Tue Mar 20 2018

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

A closed low near 33N 139W in GOES water vapor imagery is nearly
stationary with a pair of surface lows, one to NW near 35N 142W
with a 1000 mb center moving SW and a stronger low 32N 138W with
a 992 mb center moving NE. A stretched out and dissipating
occlusion extends N of the northern center E toward a secondary
low center near 38N 129W. The secondary low has an associated
frontal system bowing E over the central PZ6 waters. An E to W
ridge lies across the northern PZ5 waters while a gale center
near the southern Alaska coast has an associated cold front
approaching the NW PZ5 waters. So far have only the A version of
ASCAT which shows a band of 20 to 30 kt ahead of the occlusion in
the northern PZ6 waters and light winds in a high pressure area
in the southern PZ6 waters. A swath of N to NE retrievals appears
in Oregon waters south of the ridge, and winds are light in the

The 12Z GFS/NAM are in good agreement with the 12Z
ECMWF/UKMET/global GEM through Fri and then agreement continues
Fri night into Sat night between the 12Z GFS/UKMET/ECMWF with the
track/timing and strength of a strong but weakening low crossing
the PZ5 waters on an ESE track, while the 12Z GEM tracks the low
about 120 nm to the N and slightly faster. Prior to this, a
closed low will drop SSE from the Gulf of Alaska and with its
associated cold front moving over the offshore waters, will cause
the upper low and surface low(s) west of California to accelerate
NE and then move along the coast from northern California
northward. Have slightly above average confidence in a period of
northerly gales behind the cold front in the central and northern
PZ6 waters Wed night into Thu and then westerly gales at least in
the outer northern PZ6 and SW Oregon waters Fri night as the
strong although weakening low moves through the central PZ5
waters. Used the 12Z GFS 10m/30m winds for the wind grids through
Fri using a tool that places the stronger winds in unstable
areas. For Fri night and Sat noting model differences in track of
the low in the PZ5 waters, used a 2:1 blend of the 12Z CMC GEM
with the 12Z GFS with WPC favoring track closer to CMC global.
After Sat used the 12Z ECMWF which has been consistent building a
ridge W and N of the PZ6 waters.

Seas...The seas appear well initialized by 12Z ENP WW3 and 12Z
ECMWF WAM and they are close. Used the 12Z ENP WW3 through Thu
followed by a 50/50 blend of the two models Thu night through Sat
with some edits in PZ5 waters taking into account the blend with
the more northern low track of the 12Z GEM Fri night and Sat.
After Sat transitioned to the 12Z ECMWF WAM as ECMWF was used for



.PZ5 Washington/Oregon Waters...
.PZZ915...Outer Waters from Florence OR to Point St. George...
     Gale Possible Friday night.

.PZ6 California Waters...
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Wednesday night.
.PZZ925...Outer Waters from Point Arena to Pigeon Point...
     Gale Wednesday night.
.PZZ930...Outer Waters from Pigeon Point to Point Piedras Blancas...
     Gale Wednesday night into Thursday.
.PZZ940...Outer Waters from Santa Cruz Island, CA to 120W...
     Gale Wednesday night.


.Forecaster Bancroft. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.