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
AGPN40 KWNM 220932

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
232 AM PDT Sun Apr 22 2018

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

There is still no ASCAT data available. Conditions across the
eastern Pacific continue to remain quiet during the upcoming
week as a stable pattern prevails across the region with
primarily NW flow across the waters. During the next several days
the largest influence on the wind and sea conditions will occur
along the northern California coast as a low pressure trough
persists while a ridge axis continues to the NW. There could be a
brief period of gales over the next 24 hours (into Sun night),
mainly in the coastal zones. Again no ASCAT to confirm existance
or extent of any northerly gales near present time when the
models have been showing the gradient between the high and trough
is at a maximum. The gradient will likely be maintained into
early Sun night then weaken after 24 hours as the upper ridge
shifts toward the coast resulting in the high re-forming inland
over southern British Columbia while maintaining a weakening
ridge over the waters. In the near term used a 50/50 blend of the
00Z GFS 10 meter and higher first sigma level winds through Mon
and 10 meter winds Mon night through Tue night. A weak upstream
cutoff low center is expected to form just west of the northern
PZ6 waters by midweek and remain nearly stationary through Thu
night before drifting N and dissipating. The 00Z global models
are all in pretty good agreement over much of the period with
some differences noted in the position of the cutoff low
developing late Wed. For this reason transitioned from the
representative 00Z GFS to the 00Z UKMET on Wed which is in the
middle of the guidance through Thu night and is close to the
latest WPC medium range guidance. After Thu the models diverge on
the handling of the low with 00Z global GEM moving the low N too
quickly while 00Z UKMET/ECMWF are close and GFS drops the low
SE. After Fri when the UKMET is not available transitioned to the
00Z ECMWF through day 7.

Seas...both the 00Z ENP WW3 and 00Z ECMWF WAM initialize within a
foot or so of observed conditions and offer reasonable
solutions through Tue night. I will populate the wave grids
using the 00Z ENP through 18Z Mon and then blend on a 50/50 or
even basis starting 21Z Mon when the two models develop
differences of 1 to as high as 3 ft in the NW waters and continue
using such a blend WED through Thu night when differences between
the preferred 00Z UKMET and 00Z GFS are taken into account.



.PZ5 Washington/Oregon Waters...

.PZ6 California Waters...


.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.