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017
AGPN40 KWNM 240233
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
633 PM PST Thu Feb 23 2017

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

The 00z surface analysis indicated a weak high pressure ridge
across the area, with weak low pressure west of the Washington
and Oregon offshore waters. The main forecast concern continues
to be later Saturday into Sunday evening as there continues to be
a large spread among the models. The 18z GFS and NAM were both
similar to their previous 12z cycles. Both continue to indicate a
weaker low moving across the area and keep winds below gale. At
the present time not planning on making any changes to the
existing wind grids and will continue to cap winds at 30 kt,
although with the trend of the 12z ECMWF compared to previous
runs it appears gales may be a possibility with the best
chance over the central California waters. A quick glance at the
new 00z NAM indicates it is close to the 12z ECMWF. The 00z sea
state analysis indicated that observed seas matched up well with
both the MWW3 and ECMWF WAM, and will also not be making any
changes to wave grids.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

At 18z a high pressure ridge was located across the PZ5 and PZ6
offshore waters. Latest series of ASCAT high resolution passes
revealed 10-20 kt winds over the PZ5 waters with 15-25 kt winds
over the central CA waters.

In terms of the latest round of guidance through roughly Sat 12z
the models continue to remain in good agreement with high
pressure ridging over the waters giving way to a weak low moving
north to south across the PZ5 waters into the northern PZ6 waters
Fri into Sat. With that in mind favored 12z GFS 30m winds through
roughly Sat 12z. Beyond that frame differing solutions persist
in regards to whether or not a strong low will move west to east
across the central CA waters Sat night into Sun. The 12z ECMWF
has come back a bit stronger with the low as compared to its 00z
run...bringing it closer to 12z UKMET/CMC solutions which have
been persistent in showing a strong low. In fact the 12z ECMWF
is now suggesting gales over parts of the central CA waters as
the low moves through as well. With all the back and forth seen
in the guidance over the last several days including the 12z
ECMWF now shifting towards the stronger low scenario am not
comfortable with changing the Sat/Sun forecast as I want to avoid
flip-flopping forecast wise. Hence from Sat 15z through Tue 12z
left ongoing grids as is...then transitioned back to 12z GFS from
Tue 15z on.


.SEAS...Populated grids through Sat 12z with 12z NWW3
transitioning to ongoing grids afterwards.


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



.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
     None.

.PZ6 California Waters...
     None.

$$

.Forecaster Kosier/Holley. Ocean Prediction Center.



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