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AGPN40 KWNM 232035
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
135 PM PDT Thu Mar 23 2017

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


Grids: 12z GFS into Saturday night, then a transition towards the
12z ECMWF thereafter. Discussion follows.

GOES W providing spectacular visible satellite imagery this
afternoon of strong low pressure lifting northeast towards Haida
Gwaii, while at the same time pulling a rather strong frontal
boundary east across the northern offshore waters of the E
Pacific. For the past several days leading up to the event,
including recent regional runs of the HRRR and 4km NAM, forecast
models have been outstanding and consistent pinpointing the
timing and strength of the passing front. A very fortunate ASCAT
MetOp-B overpass just after 18z today returned great coverage of
the frontal boundary, and as expected widespread gale force
winds were detected over portions of all OPC offshore zones
north of about 40n. These winds continue to be well resolved in
latest GFS output. Hourly GFS and 4km NAM sweep the front and its
associated gales east of the OPC AOR just after 03z this
evening. Still expect strongest winds to 40 kt across the inner
OR waters around and after 21z today associated with
strengthening low level jet as the front draws nearer to the
coast. Highest winds should remain within the coastal zones,
where gusts exceeding storm force possible in the waters adjacent
to to Cape Blanco.

Farther south, the same ASCAT overpass did contain a several 30
kt wind retrievals in the vicinity of, and due south of the
Channel Islands. Will make the necessary minor adjustments in the
initial GFS grids to ensure 30 kt are in the tonight portion of
zone 840.

After late Saturday night, official forecast grids will transition
closer to the 12z ECMWF. For the past several days, the Euro has
remained very consistent bringing another cold front over the
northern offshores Sun and Sun night. The GFS has vacillated
between wildly differing solutions for several cycles in a row,
most notably at one point forming a sub 995 triple point stalled
low over the WA waters. Models are seemingly converging on a
consensus solution for timing of the front, but again, feel it
best to use the more stable ECMWF. And based on the uncertainty
still present, will continue cap pre-front winds to 30 kt. Would
not be surprised to see warning headlines added as the event
draws nearer - and confidence increases.

Mon through Tue night: all guidance suggests a strong pressure
gradient setting up between building EPAC high pressure and
forming low over the interior Great Basin, with widespread
prevailing n-lies over OPC zones south of about San Francisco
Bay. With models continuing to signal this strong gradient, feel
comfortable bumping up max winds to the 30 kt threshold. Should
models remain consistent, would expect to see gale warning
headlines introduced at some point.

Seas: in similar fashion to the wind grids, will use the WW3 ENP
into Sat night, then transition towards the ECMWF WAM thereafter.

Extratropical storm surge guidance: n/a.


.WARNINGS...Preliminary.

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

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

$$

.Forecaster Collins. Ocean Prediction Center.



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