Marine Interpretation Message
Issued by NWS
AGPN40 KWNM 251505
Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
805 AM PDT Sat Mar 25 2017
.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.
The satellite images show low clouds covering most of the region
with higher clouds now moving east into the central and northern
waters. The lightning density map show very few strikes and
mainly over the central waters. The SREF model has PROB 0 for
severe TSTMS across the region and in the short term the model
suggest only PROB 5 for severe TSTMS over the eastern portion of
the forecast waters adjacent to WA and OR. The latest
observations show higher winds mainly over the far south-eastern
waters at 20 kt. Winds range between 5 and 15 kt over the rest
of the region with relatively lower winds over the central waters
in the vicinity of the ridge axis. At 12Z the NCEP map has a
weak high pressure 1022 mb over the central waters that is part
of the main high 1026 mb about 600 NM SW of the central waters.
A cold front stretches southwest across the far southern waters
from inland low pressure over southern California. The seas have
peak at 13 ft over the washington waters while they range
between 6 and 12 ft over most of the region with relatively
smaller seas over the southern waters. The wave models NWW3 and
ECMWFWAVE have matched the observed seas pattern very well and
both models have been quite consistent in the previous runs. For
this update will continue to stay close to NWW3 wave model.
In the upper levels, the models GFS/CMC/UKMETHR/ECMWFHR suggest
an upper-level trough with some energy stretching south from the
Gulf of AK along the Canada and US coastline. An upperlevel
ridge is just behind the trough with very little energy. Farther
west, the models suggest mainly zonal flow south of 35N with some
significant energy embedded in upper level troughs north of 35N
that will move into the north waters Sunday and will result in a
tight pressure gradient and elevated winds over the northern
The models GFS/CMC/UKMETHR/ECMWFHR/NOGAPS/NAM/GFSMEAN have
initialized well the 12Z surface observations with just minor
differences on the pressure field within 2 MB on the central
pressure value for the high over the southern waters. There are
also minor differences on wind speed within 5 kt. Otherwise, the
models are in a fairly decent agreement on the general synoptic
pattern and sequence of features that will impact the region in
the short term. Though for this update, will not make major
changes to the previous forecast, will monitor the southern
waters for possible gales about Tuesday in the afternoon
issuance. Will continue to use the GFS guidance for this update.
In the short term, the high pressure over the central waters will
weaken and dissipate as the main High pressure center moves
southeast. The cold front over the southern waters will weaken as
it moves southeast and dissipate.
At 06z a high pressure ridge extended across the PZ5 waters down
into the northern and southern parts of the PZ6 waters. A cold
front extended northeast to southwest across the central PZ6
waters. ASCAT high resolution pass from near 0555z revealed 10-20
kt winds over the PZ5...most of the PZ6 waters w of 121w...except
for the inner central PZ6 waters were winds as low as 5 kt were
Continued good agreement through Mon morning when viewing the
00z model package...hence populated through Mon morning with the
00z GFS which still results in current warning headlines
remaining in place. Good confidence in pre-frontal gales ahead of
the cold front progged to move through the waters Sat night into
Sun. Beyond that period there are some differences in regards to
exact location and timing of low pressure expected to slide
somewhere north of the PZ5 waters Mon night into Tue with the 00z
UKMET having the strongest solution at the moment.
However...despite the differences to the north...further south of
the PZ6 waters guidance remains in good agreement in terms of
strengthening north to northwesterly winds across parts of the
central and southern PZ6 waters as the pressure gradient tightens
in response to inland troughing and a high pressure ridge to the
west. That said because of the differences noted over the PZ5
waters feel it`s reasonable to not make adjustments to the grids
at all beyond Mon morning at this point. Hence winds will
continue to remain below warning criteria over parts of the
central and southern PZ6 waters for now...though again
possibility of gales will continue to be monitored.
.SEAS...Populated using 00z NWW3 through about Sun 06z then from
Sun 12z on continued with ongoing grids which consisted of blend
of the 12z NWW3/ECMWF WAM with additional adjustment to the seas
in the pre-frontal gales.
.EXTRATROPICAL STORM SURGE GUIDANCE...n/a.
.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
Gale tonight into Sunday.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
.PZZ810...Inner Waters from Cape Lookout to Florence OR...
.PZZ815...Inner Waters from Florence OR to Point St. George...
.PZ6 California Waters...
.Forecaster Musonda/Holley. Ocean Prediction Center.