marine weather discussion for N Pacific Ocean

NWS ocean prediction center Washington DC

645 am PST Sat 21 Nov 2009

.Forecast discussion: major features/winds/seas/significant

.Weather for the North Pacific N of 30n and E of 150w.

06z GFS continued trend from prev run of a brief period of 50 kt

winds dvlpg in the SW and W quad of low progged to move across

the nrn or waters tonight. 00z ECMWF and UKMET do show sfc winds

of 40 to 45 kt which adding the 5 to 10 kt low wind bias these

models usually show would also support minimal storm conditions.

Also looking at model soundings...atmosphere relatively unstable

and would psbly allow 50 to 55 kt winds at 950 to 925 mb mix

down to the sfc. With relatively good agrmt with the glbl models

and the fact that the event is about 18 to 24 hours away...will

go ahead and upgrade warning in the or waters to storm for

tonight in the next package. But looks like storm conditions

will only last for a brief time as low intensifys and moves

quickly across the offshr and cstl waters.

Otw...no sig changes expected in the remainder of the fcst.

Seas...ww3 looks good across the cstl/offshr waters when

compared to latest sfc obs.

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Previous discussion...

06z NCEP prelim surface analysis shows high pres ridging over

much of the offshore waters...while a dissipating cold front was

located over the srn CA waters. 0316z qscat pass indicated the

strongest winds...20-25 kt...were located from the N part of the

central waters N thru the pz5 waters.

Cold front currently about 250 nm W of the pz5 waters slides

thru the waters today and into the N...central CA waters tonight

into sun. 00z GFS continues to indicate pre-frontal gales along

W/the 00z CMC/NAM while the 00z ECMWF/UKMET Max out at 30 kt. A

secondary low is expected to develop behind the front and move

thru the pz5 waters late tonight into early sun W/model support

from all but the 00z NOGAPS. 00z GFS is now suggesting risk of

small area of storm force winds in the far N or waters

respectively. Other global models indicate winds of 40 kt with

the 00z ECMWF reaching 45 kt. Debated upgrading Sat night Gale

Warning to storm for or waters but for now will hold off given

this is the first run which such a wind increase...but I will

increase winds to 40 kt in the far S WA waters...and to 45 kt

across the entire or waters Sat night. Given the agreement among

models for pre-frontal gales and even stronger gales Sat night

in association with the secondary low will update warning confdc

levels to MDT to high in the pz5 waters.

Winds relax sun as high pres ridging moves overhead W/the next

frontal system approaching Mon. Models have come into better

agreement concerning timing of frontal passage and push the

front thru the pz5 waters by late Mon. Good model agreement on

pre-frontal gales late sun into Mon in WA...far N or waters.

Confdc levels already at low to MDT in the WA waters...so will

increase levels in the or waters to the same. Next system

approaches waters Tue with decent agreement amongst models this

far out. 00z GFS/CMC spread gales into the WA waters Tue and far

NW or waters Wed...with the 00z UKMET/ECMWF at 30 kt. Will

continue with low confdc gales in place in WA waters. Will not

yet add gales into the or waters Wed given its day 5 and current

coverage appears to be minimal as stated earlier.

Seas...00z ww3 was within 1-2 ft of observed ship/buoy obs at

00z and again when the 06z forecast was compared to obs from the

same time. Therefore will generally favor ww3 thru the forecast

period.

.Warnings/forecast confidence...Warnings are preliminary and are

subject to change. Any changes will be coordinated through AWIPS

12 planet chat or by telephone.

.Pz5 Washington/Oregon waters...

.Cape Flattery to Cape Lookout...gale today into sun...MDT to

high confdc. Gale Sun night into Mon...low to MDT confdc. Gale

Tue into Wed...low to MDT confdc.

.Cape Lookout to point St George...Gale today into sun...MDT to

hi confdc...with storm tonight...MDT confdc. Gale Sun night into

Mon...low to MDT confdc.

.Pz6 California waters...

.Pt St George to pt Arena...none.

.Pt Arena to pt Conception...None.

.Pt Conception to Guadalupe island...None.

.Forecaster achorn/Holley. Ocean forecast branch.