Marine Interpretation Message
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
AGPN40 KWNM 240327
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
827 PM PDT Mon Oct 23 2017

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

For the winds, no changes are planned for the evening update
with the latest 18Z GFS in very good agreement with its previous
run (on which the current grids are based) and with the 12Z
global models and 18Z/00Z NAM. Only the NAM shows gale force
boundary layer winds off northern CA Wed night as the ridge
builds back NW of the PZ6 waters models, and is discounted. A
high pressure ridge will dominate over the Washington, Oregon and
northern California waters through the period, while trough
along the California coast strengthens the next few days before
weakening later Wednesday through Friday, with winds becoming
light.

Seas...The 00Z sea state analysis indicated that observed seas
are closest to the 12Z/18Z Wavewatch III which initialized with
slightly higher seas than the 12Z ECMWF WAM. Plan to retain the
present seas into Fri based on the 12Z Wavewatch III except boost
the seas in the first period by 15 percent from the far southern
PZ5 waters southward to produce a closer match to the surface and
satellite-based observations.
-----------------------------------------------------------------
PREVIOUS DISCUSSION...

The 18z surface analysis indicated a high pressure ridge over the
Washington, Oregon and northern California waters with a trough
extending along the California coast. An ascat pass from around
1740z with limited coverage mainly over the central and southern
California waters indicated a small area of 30 kt over the
northern California coastal waters. Otherwise, winds were mostly
in the 15 to 25 kt range which matches up well with model
forecast fields.

The 12z models continue to be in very good agreement through the
forecast period. During the short term period tonight through
Thursday night, the models all continue to indicate the ridge
over the Washington and Oregon waters builds west while the
trough along the California coast expands north along the Oregon
and Washington coast through Tuesday night. A weak cold front
will move across the Washington and Oregon waters Wednesday
before dissipating Wednesday night. Winds with this front will
remain well below gale with this front. Weak low pressure will
then move over the Oregon coastal and offshore waters Thursday
and Thursday night then move into the Washington waters and
eventually dissipate Friday. Then looking ahead to Friday night
and beyond there are some differences with placement of lows,
however these are west of the offshore waters and in general the
models agree on a weak high pressure ridge across the waters.
There seems to be better agreement between the 12z GFS/UKMET/CMC,
so will use the GFS 10m winds through the period.

.SEAS...The 18z sea state analysis indicated that observed seas
were within a foot of the WaveWatch III forecast values, and plan
on using the WaveWatch values through 12z Friday. For Friday
through Saturday night, the WaveWatch values look a bit high, so
will use a blend of the WaveWatch and ECMWF WAM during that
period.

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

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
     None.

.PZ6 California Waters...
     None.

$$

.Forecaster Bancroft/Kosier. Ocean Prediction Center.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.