marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 720 PM PST Sat 22 Nov 2014
.Forecast discussion: major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
18z GFS continued to indicate marginal gales over outer waters N of Cape Shoalwater ahead of cold front tonight. However given marginal nature of event and relatively stable low levels will drop warning over Cape Shoalwater to Cape Lookout pzz905 waters. 18z GFS and 18z NAM were generally consistent with respective previous runs. 18z GFS trended toward 12z ECMWF and was a bit weaker with pre frontal winds toward end of forecast period Wed night and Thu. Will not be making much adjustment to previous grids in this evenings updates.
18z multigrid wavewatch iii is a few ft too high with sig WV hgts W and NW of nrn pz5 waters this evening...within area of gales which will move into these offshore waters tonight.
---------------------------------------------------------------- ...Previous discussion...
Over the short term...the new 12z mdls remain in good agrmt that the cold front now acrs the cntrl CA ofshr wtrs wl drift S into the srn pz6 wtrs tonite then dispt sun. At the same time as the mdls all fcst a high pres ridge to bld into the nrn pz6 wtrs tonite/sun they fcst the nly gradient acrs the cntrl/srn pz6 wtrs to strengthen (gnrly up to 25 or 30 kt). Further N the 12z mdls remain consistent in fcstg a nrn stream sfc low to dvlp and pass N of the pz5 wtrs tonite whl pulling a wkng ascd front and/or sfc trof into the nrn wtrs tonite/early sun. With all of the 12z mdls except the usually conservative 12z ECMWF...which fcsts 25-30 kt bl winds...fcstg a brief period of gale force bl winds ascd with this front/trof wl cont with the prevly fcstd mod to hi confidence gale wrngs for the pz5 wtrs for tonite (at the same time per a consensus of the 12z mdls stil believe these gales wl remain limited to the pz5 ofshr wtrs and wl not make it into the adjacent cstl wtr domains). Later sun/sun nite as the mdls fcst the area of high pres to expand the mdls to slighly varying degrees all fcst the gradients to both its N and S to weaken so it wl just be a matter of how fast to fcst conds to dmnsh. Then Mon/Mon nite whl the mlds fcst the high pres ridge to cont to dominate the pz5 wtrs they fcst with varying timing a warm front to lift NNE acrs the pz5 wtrs with a strenthening ascd sswly gradient dvlpg. On Mon nite the 12z GFS fcsts a frontal wave to dvlp and as a result fcsts its warm front to pass N of the pz5 wtrs...which is sprtd by the 12z navgem. But with the 12z gefs indicating that the 12z GFS frontal wave is lkly too strong... wl instead favor a blended 12z UKMET/ECMWF solution (which is sprtd by the 12z Gem and the latest wpc medium range guidance) which does not fcst the warm front to lift as far N Mon and then stalls acrs the nrn most pz5 wtrs Mon nite. So for the short term...smlr to what was done prevly...plan on populating our fcst wind grids with the 12z GFS 30m bl winds for tonite/sun...then wl transition to the 12z ECMWF bl winds for sun nite thru Mon nite. So as a result wl be making gnrly small short term chngs to the prev ofshr fcsts.
In the long range...on Tue/Tue nite...without particulary high fcst confidence other than to remain mr consistent with the wpc medium range guidance wl favor the 12z ECMWF solution of the warm front drifting N whl a weak frontal wave races E along it. Therfore wl cont to populate with the 12z ECMWF bl winds for Tue/Tue nite. Then Wed thru Thu nite the differences btwn the 12z GFS and 12z ECMWF narrow sigly as they both fcst smlr tracks for a closed upr low and its ascd nrly vertically stacked sfc low to slowly meander ENE twds the nrn ofshr wtrs with an ascd front movg into the nrn wtrs Wed nite into Thu nite with a gradly strengthening ascd ssely gradient. With the 12z GFS fcstg a smlr but stronger gradient than the 12z ECMWF blv for now a compromise btwn the two mdls wuld be best. Therefore for Wed thru Thu nite plan on populating with a 50/50 blend of the 12z GFS 10m and 12z ECMWF bl winds which wl result in no ascd psbl wrngs (which are hinted at by the 12z GFS 30m bl winds N of the front acrs the nrn pz5 wtrs late Thu/Thu nite).
.Seas...Since the 12z GFS wl be favored...wl populate our fcst seas with the 12z wavewatch iii for tonite into sun nite...which are very smlr to the 12z ECMWF wam fcst seas. Then since the 12z ECMWF solution wl be favored...wl transition to all 12z ECMWF wam fcst seas for late sun nite thru Tue nite. Then since a blend of the 12z GFS/ECMWF wl be used...wl populate with a 50/50 blend of the 12z wavewatch iii and 12z ECMWF wam for Wed thru Thu nite.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... .pzz900...outer waters from Cape Flattery to Cape Shoalwater... gale tonight.
.Pz6 California waters... None.
.Forecaster Clark/vukits. Ocean prediction center.