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000
AGPN40 KWNM 221447
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
747 AM PDT Sun Oct 22 2017

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

With continued model agreement and forecast consistency, will
not make any major changes to the forecast for this update.

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PREVIOUS DISCUSSION...

Latest 0445Z and 0545Z ASCAT passes show SW gales ahead of a
cold front over the Oregon waters while the low pressure center
analyzed in 06Z NCEP analysis near 53N 140W has westerly gales
associated with it which according to ASCAT extended east to 130W
in Washington waters. A comparison of the ASCAT wind pattern with
00Z GFS boundary later winds suggests an even blend of the 10m
and first sigma level winds appears representative of conditions
in near term. With is in mind plan to use such a blend for the
new forecast through 15Z in first period and as a result plan to
add gale warning to PZZ900 for start of forecast and will carry
SW gale ahead of front in PZZ815 and PZZ810 in 09Z grid but by
12Z gales should be confined to coastal waters ahead of the front
and the low pressure to the NW will weaken while moving NE so the
westerly gales in the far NW will end early this morning.

00Z model agreement is good through 5 days except the 00Z GFS is
still a bit slower with the cold front moving into the PZ5
waters Tue night into Wed night while the 00Z ECMWF remains
consistent with timing and strength and close to 00Z GEM and WPC
medium range guidance. Apart from using the 00Z GFS 10m winds for
much of the forecast plan to use the 00Z ECMWF boundary later
winds from 15Z Tue to 00Z Thu based on its better timing and
winds behind the front. It should be noted that a slight boost of
ECMWF winds in NW flow behind the front would result in gales in
the far NE waters Wed but with the other models weaker plan to
leave the ECMWF surface winds unchanged. Also for late Wed and
Wed night as the front moves S and ridge builds in from NW
combined with northward extension of coastal trough winds may
approach gale force off northern CA adjacent to coastal waters
but for now there is not good model consensus for gales except
perhaps in coastal waters. Will leave PZ6 waters subgale through
period.

.SEAS...00Z WW3 initialized 1-2 ft high in the PZ5 waters but
otherwise both WW3 and 00Z WAM are close to observed conditions
in PZ6 waters. Plan to use an even blend of the two models
through the period except when ECMWF is used for winds will use
the 00Z ECMWF WAM.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
     Gale today.

.PZ6 California Waters...
     None.

$$

.Forecaster Sommerville/Bancroft. Ocean Prediction Center.



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