Marine Interpretation Message
Issued by NWS
AGPN40 KWNM 010322
Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
822 PM PDT Sun Apr 30 2017
.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.
At this time I dont plan on making any changes to the current
grids or associated text forecast. over the next couple of days
the potential for gales will exist in coastal regions along the
central and northern California coast. I am not expecting gales
to spred to the offshore waters.
There are no warnings through the forecast period over the
forecast waters but seas will still build over the north waters
in the extended period as strong low pressure slated to reach the
Gulf of Alaska passes to the northwest of the region. The
satellite images still show anticyclonic flow over most of the
forecast waters except the far north waters which is still
dominated by clouds with cold tops. The lightning density map
also shows no lightning strikes across the region and even the
SREF model has continued with PROB 0 for TSTMS threat. The latest
observations including scatterometer passes at 1727Z indicate
higher winds only to 25 kt in a few areas over the far north and
south waters. At 1800Z, the NCEP map has a cold front across the
northern California waters that passes through high pressure to
the west resulting in two centers 1032 MB just west of Oregon
waters and the second center 1034 MB about 300 NM west of central
California waters. Low pressure 1011 MB along 140W north of the
region. Inland trough stretches near the coast from south
California to 38N. The central and western pacific ocean is still
dominated by low pressure with several centers. One complex low
pressure is in the Bering sea with another low 1007 MB east of
Japan near 170E and this low is on track to reach the Gulf of
Alaska and bring storm force winds there but will also bring
large period swell to the north forecast waters.
The models GFS/CMC/ECMWFHR/UKMETHR in the upper levels indicate
a cut off upper level high pressure along 30N and extends its
ridge north through the western portion of the forecast region.
There is still a cut off low with some energy over the Hawaiian
Islands and also over the Aleutian Islands. The models agree well
on maintaining upper level high pressure ridge over the region
that will block energy from the west to reach the waters but will
instead glide northeast and end up in the Gulf of Alaska.
The models GFS/CMC/ECMWFHR/UKMETHR/NAM/NOGAPS have generally
initialized well the 18Z surface observations and the small
differences are mainly within 2 Mb on the central pressure value
for the high pressure to the west of Oregon. The ECMWFHR is the
weakest with wind speed. Otherwise the models still have these
minor differences through the short term but do not alter the
general synoptic pattern and so will continue with GFS. In the
short term, the high pressure center west of Oregon waters will
pass east across the region and dissipate inland while the high
pressure center west of the southern waters will remain in the
same vicinity and maintain a ridge across the region with a
relaxed pressure gradient. There will be no warnings through the
.SEAS...The seas range between 6 and 10 ft over the north and
south waters but they range between 4 and 6 ft over the central
region. Peak seas to 12 ft are over the far north waters. The
wave models NWW3 and ECMWFWAVE have initialized the observed seas
pattern very well and have been very consistent in the previous
runs and so no need to deviate from the previous model choice.
Will stay with ENP for seas.
.EXTRATROPICAL STORM SURGE GUIDANCE...n/a.
.PZ5 Washington/Oregon Waters...
.PZ6 California Waters...
.Forecaster Shaw/Musonda. Ocean Prediction Center.