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000
AGPN40 KWNM 220746
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
1146 PM PST Tue Feb 21 2017

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

Over the short term, in response to a high pressure ridge
forecast to build to the W of the offshore waters and a series
of upper level short wave troughs diving SE across the Wrn conus
causing lower pressures, the 00Z models to slightly varying
degrees all forecast the NWly gradient throughout the
coastal/offshore waters to strengthen today into tonight
(especially across the central/Srn PZ6 waters), then gradually
weaken late Thu/Thu night. Therefore, plan on populating our
forecast wind grids with the representative and slightly stronger
00Z GFS first sigma level winds for this gradient for today
through Thu night since they are well supported by the other 00Z
models, especially the 00Z NAM/GEM. So per these winds (and the
00Z NAM first sigma level winds) can not rule possible gales in
the coastal water domain near the Channel Islands tonight, but
further offshore will keep winds subgale for now.

In the long range, would favor a solution close to the similar
00Z GFS/ECMWF/GEM for a weak surface low (with max winds
generally up to 20-25 kt) to track S across the PZ5 waters
Fri/Fri night, then dissipate Sat. So will continue to populate
with 00Z GFS first sigma level winds for this system for Fri
through Sat with some minor additional edits in deference to the
00Z ECMWF.

Then as has been the case for their past several runs, the
disparity between the 00Z global models increases significantly
Sat night into Sun night in regards to a potentially strong
surface low tracking E into the PZ6 waters. Versus its previous
18Z run, the 00Z GFS remains consistent in forecasting a strong
low to track E across the central PZ6 waters late Sat
night/Sun...then move inland Sun night with widespread gale and
storm force associated boundary layer winds. In regards to the
forecast track of this system, the 00Z GFS track, which is
supported by the 00Z GEFS Mean, looks like perhaps a reasonable
compromise between the more Nrn 00Z UKMET and more Srn 00Z
ECMWF/GEM solutions and is in line with the latest WPC medium
range guidance. In regards to the forecast strength of this low,
the consistent 00Z ECMWF continues to look like a weak outlier
solution while the 00Z GFS, though supported best by the 00Z
UKMET, per the 00Z GEFS Mean is perhaps somewhat too strong.
Therefore, will favor the 00Z GFS solution for this system and
similar to the previous forecast package will populate with our
smart tool that will place stronger 00Z GFS first sigma level
winds in unstable areas and weaker 00Z GFS 10m winds in stable
areas for Sat night through Sun night. But, then in deference to
the weaker 00Z GEFS/ECMWF solutions will cap these winds at
40-45 kt to hold off on forecasting any possible storm warnings
for now.

.Seas...A compromise between the very similar 00Z Wavewatch III
and 00Z ECMWF WAM initializes the current seas best at the
moment. With this in mind and with their associated 00Z GFS/ECMWF
solutions remaining similar, will populate our forecast wave
grids with a 50/50 compromise blend of the 00Z Wavewatch III and
00Z ECMWF WAM for today through Sat. Then since the 00Z GFS
solution will become favored, will transition to populating with
all 00Z Wavewatch III seas for Sat night through Sun night (will
not adjust these forecast seas downwards because if the 00Z GFS
forecast winds do verify then these seas will likely be too low
over the PZ6 waters).

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

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
     None.

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
     Gale Possible Saturday night.
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Possible Saturday night.
.PZZ825...Inner Waters from Point Arena to Pigeon Point...
     Gale Possible Saturday night.
.PZZ925...Outer Waters from Point Arena to Pigeon Point...
     Gale Possible Saturday night.
.PZZ830...Inner Waters from Pigeon Point to Point Piedras Blancas...
     Gale Possible Saturday night.
.PZZ930...Outer Waters from Pigeon Point to Point Piedras Blancas...
     Gale Possible Saturday into Saturday night.
.PZZ835...Inner Waters from Point Piedras Blancas to Santa Cruz Island, CA...
     Gale Possible Saturday night.
.PZZ935...Outer Waters from Point Piedras Blancas to Santa Cruz Island, CA...
     Gale Possible Saturday night.

$$

.Forecaster Vukits. Ocean Prediction Center.



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