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AGPN40 KWNM 191536

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
836 AM PDT Mon Mar 19 2018

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

12Z NCEP surface analysis shows a weak high pressure ridge over
the offshore and coastal waters. Latest observations and last
ASCAT passes show light winds except SE 20 to 25 kt over the far
W portion of the central PZ6 offshore waters. Those higher winds
are at the outer edge of a strong upper low and associated
complex surface system with the main surface center analyzed
near 36N 139W with a 992 mb center. Associated occluded front and
cold front has bowed east to near 31N 134W. The 06Z GFS is well
initialized with this surface pattern and with current wind grids
based on the 00Z 10m/30m winds see no need to update with the
newer 06Z GFS as the GFS remains consistent and is in good
agreement with the 12Z NAM and other 00Z global models through
Fri. Currently carrying marginal gales in the outer central PZ6
waters tonight as the aforementioned front enters the waters, but
with only marginal support from other models have below average
confidence in warnings for tonight. Models diverge more after Fri
and for that time frame repopulated grids with the 00Z ECMWF
which is in good agreement with the GEFS and ECMWF ensemble means
and latest WPC medium range guidance.


High pressure over the southern waters will move east inland as
low pressure strengthens west of the southern region and will
move northeast into the central and northern waters forcing winds
to be elevated to gale force threshold. The NCEP weather map at
06z has high pressure 1021 MB over the southern waters while low
pressure 1021 MB is centered over the Washington waters. pressure
gradient is very relaxed across the region and maximum observed
winds are only 15 kt in areas mostly over the northern waters.

The energy indicators show a pocket of energy over the northern
waters that is associated with surface low there. More energy is
embedded in upper level cutoff low over the Pacific ocean near
140W that is associated with surface low there too. In the short
term, the energy over the north waters will thin out as low
pressure moves inland while over the Pacific, the energy will
shift east toward the region. In the extended period there will
be more energy dropping from Gulf of Alaska and will combine with
he energy from the south.

Models GFS/CMC/ECMWFHR/UKMETHR/NOGAPS have initialized well the
06Z surface observations with just small differences on the wind
direction around the high pressure mainly in areas with light
winds. Otherwise, models agree well in the short term on the
general synoptic situation as they move low pressure into the
waters. The differences in the extended period are still small
and mainly the windspeed. Will favor model with elevated winds
and so will stay with GFS.

.SEAS...Seas have a peak at 8 ft over the far southwestern waters
and they beginning to build form the west over the central
waters. NWW3 and ECMWFWAVE models fit well the observed seas
pattern. In the short term, both wave models agree well n
building seas over the central waters and then spread into the
northern waters. seas will peak at 15 ft in the extended period.
will use NWW3 for seas.



.PZ5 Washington/Oregon Waters...

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
     Gale Possible Friday night.
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Possible Thursday night into Friday night.
.PZZ925...Outer Waters from Point Arena to Pigeon Point...
     Gale Possible Friday night.
.PZZ930...Outer Waters from Pigeon Point to Point Piedras Blancas...
     Gale tonight.


.Forecaster Bancroft/Musonda. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.