000
AGPN40 KWNM 292134
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
234 PM PDT Sun Mar 29 2020

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

18z surface analysis shows a broad area of high pressure across
the California waters that stretches inland across much of Oregon
and California this afternoon. To the northwest of the Washington
waters, a strong partially occluded low pressure at 985 mb is
centered in the eastern Gulf of Alaska near 55N139W. The
occluded front arcs from the low center to near 50N134W and
becomes a cold front southwestward to beyond 45N140W. The front
will reach the WA/OR waters tonight and northern CA waters late
tonight into early Monday. The latest 12z guidance remains in
good agreement on this timing. The low is expected to weaken
through the overnight hours as it tracks E-SE and at this time
gale force winds are anticipated to remain to the NW of the outer
northern WA waters. The possibility of gales near the coast in
the coastal waters is more likely as the front pinches along the
coast late tonight. Approaching Vancouver Island Monday and
Monday night, the low will gradually weaken as it tracks across
the island on Tuesday. After the low dissipates by late Tuesday
night, a surface trough will linger across the island through
Wednesday and Wednesday night.

Meanwhile, as the aforementioned low pressure to the N weakens,
high pressure to the W of the CA waters will slide eastward
Monday night into Tuesday. In addition, a coastal surface trough
is expected to develop across southern CA and slowly extend
northward Tuesday night into Wednesday. As the pressure gradient
between these two features strengthens, winds will increase into
a range of 25 to 30 kt. At this time, 12z model guidance
indicates no wind hazards are anticipated across the offshore
zones, however the 12z GFS and Canadian show only brief
localized possible gales Wednesday night in the vicinity of
Point Piedras Blancas in the CA coastal zones.

Thereafter, the ridge will shift gradually southward as the next
low pressure system slowly develops and moves eastward,
approaching the WA/OR waters Thursday night into Friday. Models
differ on the timing of this next system`s movement across the
offshore waters with the 12z ECMWF slower and the 12z GFS and
UKMET faster. As with previous forecast packages, have been
favoring a slower movement with this low, so have populated grids
with the ECMWF. This also maintains good continuity with the
mid-ocean forecast where ensembles favor a slower system.

.Seas...For the wave grids, utilized the 12z ENP version of
WaveWatch until 18z Thursday, then transitioned to the 12z
ECMWFWave from 18z Thursday through the end of the forecast
period. A few minor edits were made within the transition period
on Thursday where seas are in a subsiding trend off the coast of
California and beginning to slowly build to the W of the Oregon
and northern CA waters with the approach of the next system.


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


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
None.

.PZ6 California Waters...
None.

$$

.Forecaster Huffman. Ocean Prediction Center.