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AGPN40 KWNM 240944

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
244 AM PDT Tue Apr 24 2018

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

The current 06Z surface analysis shows a cold front approaching
the PZ5 waters from the NW. The front extends SW and becomes
nearly stationary W of the southern Oregon and northern PZ6
offshore waters while leading into a weak low near 40N 136W which
appears on GOES-15 water vapor imagery associated with an upper
low which appears nearly statioary. The front then continues S
from the low to 30N 140W. Over the offshore waters the ridge has
dissipated with the flow mostly northerly on the west side of a
coastal low pressure trough. Pressure gradients are relatively
weak. No recent ASCAT imagery is available, and available surface
observations in and near the coastal and offshore areas show
mostly winds 20 kt or less, in line with 00Z model fields.

The 00Z models show the aforementioned low on the front gradually
sinking S as the frontal boundary dissipates. The strongest winds
will be west of this low but winds are likely to increase behind
the front over the PZ5 waters as it enters the waters today. A
second low center will form in the low pressure trough central
or northern California and move offshore by early Wed and is
likely associated with an upper shortwave rotating around the
south and then east sides of the upper low. The weak low center
is expected to remain nearly stationary just W of the waters late
Wed through Thu night before tracking NE across the region. A NW
flow will gradually spread over the region toward the end of the
period as the upper low and associated weak surface low(s) move
inland. The 00Z global models are in pretty good agreement,
especially the 00Z GFS and ECMWF. The 00Z global GEM moves the
surface reflection of the upper low out too quickly and the 00Z
UKMET is in improved agreement with other guidance through Fri
night, but is weaker with winds in the northern waters on Day 5.
The GFS builds the high too far south Sat and Sat night relative
to other models leading to more widespread strong northerly
winds and possible gales in the far NE, and appears the outlier.
Therefore populated winds with the representative 00Z GFS 10
meter winds through Thu and then early Thu night transitioned to
00Z ECMWF for the remainder of the period.

Seas...Both the 00Z ENP WW3 and 00Z ECMWF WAM appear to forecast
reasonably well during much of the remainder of the week,
depending on their associated wind forecast. I will populate the
wave grids using the corresponding model to match the winds, with
notably the ECMWF preferred especially late in the period.



.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.