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AGPN40 KWNM 201015 CCA
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
113 AM PST Sat Jan 20 2018

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

An ASCAT-B pass just before 05Z this morning indicated weakening
low pressure has moved into the Queen Charlotte Sound, with any
associated marginal gales well north of our forecast waters.
Meanwhile, 25 to 30 kt northwesterly winds prevailed over the
southern California waters south of Santa Cruz Island. West of
the PZ5 waters, an ASCAT-A pass around 0530Z already indicated
some gales ahead of the next frontal system that will impact the
PZ5 waters later today.

Confidence is high for widespread gales over the PZ5 waters today
into tonight, reaching the northern PZ6 zones by early Sunday.
The GFS/ECMWF/UKMET as well as the hi-res regional guidance all
depict gales as the aforementioned cold front moves across the
area. Storm force winds remain possible overnight Saturday,
especially over the central PZ5 zones, as low pressure develops
along the front and races northeast. Will continue to use a
blend of the GFS 10m winds and first sigma level winds in order
to maintain some marginal storm force winds as suggested by the
00Z GFS and 00Z/06Z NAM. All of the 00Z guidance came in weaker
with a secondary low/trough that will move across the northern
PZ5 waters on Sunday, so have decided to drop the gale warning
with this feature and reduce wind speeds to 30 kt.

The 00Z GFS winds were favored through Sunday night, followed by
a transition to the 00Z ECMWF winds from Monday to Wednesday
night. The ECMWF was better supported in the medium range by the
00Z UKMET, particularly with the location of the weakening front
over the central PZ6 waters on Monday. The guidance is coming
into better agreement for Tuesday as a strengthening low west of
the PZ5 waters should track north and pull another cold front
across the area. The ECMWF remains a good compromise between the
deeper UKMET and weaker GFS, and will maintain gales ahead of
the front on Tuesday as it tracks east across the waters. The
global models diverge on Wednesday with large timing and
location differences regarding another low pressure system
moving across the PZ5 waters. For now, will stick with the ECMWF
winds but cap them at 30 kt until more model continuity is
evident.


.SEAS...The 00Z Wavewatch initialized better than the 00Z ECMWF
WAM, particularly over the Washington and Oregon offshore zones.
In fact, a 0545Z CryoSat altimeter pass still supported seas in
excess of 20 ft across the PZ5 waters, which still required a
slight boost of the Wavewatch grids early this morning. Overall,
the Wavewatch seas looked reasonable through Sunday night. By
Monday, transitioned to the WAM seas to match up with the
forecast winds. A slight reduction was applied to the seas on
Wednesday and Wednesday night since winds were capped at 30 kt
given forecast uncertainty.


.EXTRATROPICAL STORM SURGE GUIDANCE...The latest ESTOFS and ETSS
runs both depict an area of surge approaching 1 ft on Sunday
morning north of Cape Shoalwater. Elsewhere, the guidance
remains less than 1 ft as strong southerly flow parallel to the
coast should prevail ahead of the front early Sunday.


.WARNINGS...Preliminary.

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

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
     Gale tonight into Sunday.
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale tonight into Sunday.
     Gale Possible Tuesday.

$$

.Forecaster Reinhart. Ocean Prediction Center.


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