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000
AGPN40 KWNM 221450
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
650 AM PST Mon Jan 22 2018

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

At 12Z a cold front was located across the central PZ6 waters
with a high pressure ridge across the remainder of the offshore
PZ5 and PZ6 waters. The 06Z GFS/NAM were in good agreement
through Thursday day 4 with the continued differences noted on
Friday day 5. With that noted see no reasons to make adjustments
to the ongoing grids in this intermediate update given the
continued model agreement over much of the period so far. No
adjustments will be made to warning headlines in place. See
previous discussion below.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

A weakening cold front continues moving across the northern
California offshore waters per the 06Z OPC surface analysis. A
0440Z ASCAT-A pass showed a small area of winds to 25 kt ahead
of the front. These winds will continue diminishing this morning
as the front gradually dissipates over the central PZ6 waters
later today. A high pressure ridge moving across the northern
California waters today will provide a little respite from the
high winds and seas experienced over the past few days. But
afterwards, a busy pattern will prevail over the Eastern Pacific
for the rest of this week as several low pressure systems impact
the Washington, Oregon, and northern California waters.

The first low will approach the PZ5 waters tonight and track
northwest of the area while pulling a frontal system across the
waters. The 00Z GFS/ECMWF match up well with this low, beginning
the gales around 06Z Tuesday over the outer waters and continuing
over the inner waters throughout the day. Still favored the
slightly stronger GFS solution which produced winds to 40 kt
over the far northwest portion early Tuesday. The 00Z guidance
has come into much better alignment with the next gale low
expected to cross the Washington waters Wednesday night. Used a
blend of the 00Z GFS/ECMWF winds for this feature to smooth some
minor position and track differences while maintaining gales for
the PZ5 zones through Wednesday night. Forecast confidence has
increased for both of these lows based on the agreement noted
with the 00Z global guidance.

The final system is certainly the biggest challenge with this
forecast package. The 00Z GFS/ECMWF/UKMET runs all depict
deepening low pressure approaching the PZ5 waters on Friday
night. However, there is roughly 250-300 nm spread amongst the
various models by 06Z Saturday, with the GFS track well ahead of
the other models. WPC preferred the ECMWF with its medium range
forecast, and this solution places the low between the faster
GFS and slower UKMET. Therefore, have transitioned to the ECMWF
winds late in the period, which brings strong gales into the PZ5
waters late Friday night. Marine interests should closely monitor
this system in the coming days as there is already a fairly
strong model signal that this low could reach storm force by
early Saturday near/over the offshore waters.

In summary, the 00Z GFS winds were used today through Tuesday
night, followed by a blend of the 00Z GFS/00Z ECMWF winds on
Wednesday and Wednesday night. Then, the wind grids were
transitioned to the ECMWF Thursday through Friday night.


.SEAS...The 06Z sea state analysis indicated the 00Z Wavewatch
was performing better than the 00Z ECMWF WAM over the Washington
and Oregon waters this morning. A CryoSat altimeter pass just
before 06Z, along with obs from buoy 46089, supported seas to 18
ft in this region. The Wavewatch grids were favored through
Tuesday night, followed by a blend of the Wavewatch/WAM grids
beginning Wednesday, which produced seas to 26 ft over the outer
PZ5 waters Wednesday night. Transitioned to the WAM grids
Thursday through Friday night in conjunction with the wind grids.


.EXTRATROPICAL STORM SURGE GUIDANCE...The 00Z ESTOFS and ETSS
runs both depict surge nearing or slightly exceeding 1 ft along
the Washington coast north of Cape Shoalwater around 12Z Thursday
as low pressure crosses the northern waters. This guidance appears
reasonable since the official blended winds are fairly consistent
with the 00Z GFS.



.WARNINGS...Preliminary.

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

.PZ6 California Waters...
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Possible Friday night.

$$

.Forecaster Holley/Reinhart. Ocean Prediction Center.


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