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000
AGPN40 KWNM 242056
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
156 PM PDT Mon Jul 24 2017

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

Strong northerly flow continues off the Pacific coast this
afternoon between high pressure anchored offshore and a thermal
trough over California. An ASCAT-A pass just after 18Z missed the
area of potential gales, but still showed a broad swath of 25 to
30 kt winds across much of our southern Oregon and northern
California waters. In the absence of a good ASCAT pass over our
inner offshore zones, will maintain the gale warning for PZZ820
into tonight as the 12Z GFS/NAM/ECMWF depict near gale force
winds over the far northeast portion. Winds will diminish below
warning criteria later tonight as the high moves further
southwest and the gradient relaxes.

The 12Z GFS winds were favored through Thursday night as the
latest run remains consistent with itself and the overall global
model consensus. Northerly winds 20 to 30 kt will persist over
much of the northern PZ6 waters as the offshore ridge/inland
trough pattern prevails through midweek. The strongest winds
should remain confined to the coastal waters, and no gales are
expected over our offshore zones at this time.

Low pressure will approach the PZ5 waters from the west on Friday,
and this is when the GFS begins to deviate from the rest of the
global guidance. Although the low itself remains northwest of the
waters, the ECMWF/UKMET depict a deeper low and match up really
well with the timing of its associated cold front moving across
the PZ5 waters on Saturday. Therefore, have populated the wind
grids with the 12Z ECMWF from Friday through Saturday night. The
deterministic 12Z GFS has been dismissed in the long range since
it is the only model that brings Hurricane Hilary north toward
the southern PZ6 waters by Sunday. With no ensemble support for
this solution, it seems prudent to move away from the operational
GFS for the weekend.


.SEAS...A well placed 1424Z CryoSat altimeter pass over the
northern California coastal waters supported seas to 17 ft within
the northerly gales southwest of Point Saint George. With the
wave models still running several feet too low, the wave grids
through tonight required hand editing to represent the current
conditions and match the adjacent coastal waters. Otherwise, the
12Z NWW3 ENP seas were suitable Tuesday through Thursday night.
Then transitioned to the 12Z ECMWF WAM seas Friday through
Saturday night to match the forecast winds.


.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 today into tonight.

$$

.Forecaster Reinhart. Ocean Prediction Center.


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