HS 102

marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 740 PM PDT sun 19 may 2013

.Forecast discussion: major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.

No major changes are planned for the evening update. The 06z GFS was similar to the previous 12z run...and was also close to the 12z ECMWF/UKMET/Gem. The 00z opc sfc analysis indicated low pres W of the WA/OR waters with a warm front extending to the E. The models all continue to be similar moving this low E the next 24 to 48 hours into the or waters by late Mon night...then dissipating Tue morning. The current warning headlines look very good and will leave as is. The 00z sea state analysis indicated that the observed seas were within a ft of the multi-grid nww3 fcst values.

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Previous discussion...

The ltst GOES WV imgry indc upr rdg movg E nr 135w...with raised h5 hgts alng coast enhancing cstl trof. Crnt sfc rprts indc 25 kt alng the coast with gusts nr gl frc...and the GFS cont to indc a vry mrgnl gl scenario for tngt with a fairly stg pres grad in place with high pres W of the wtrs interacting wtih the cstl trof. The 12z NAM/Gem also indc gales...and are a ltl more widespread with them. The typically cnsrvtv 12z ECMWF/UKMET indc abt 30 kt Max...so gales are within the realm of psblty. Attm feeling that a bf pd of gales shud be xpctd in the nrn and c cal wtrs tngt...as the upr rdg movg in FM the W shud enhance the sfc high pres enuf to produce gales. Also...crnt sfc rprts and oscat indc fairly sig wnds already...so confdc is MDT. The prev fcst carried gales...so wl cont in the next fcst.

The 12z mdls are trending twd a smlr soln with the shrtwv movg into the N ptn Mon ngt and Tue...and the assoc sfc low movg thru the ofshr wtrs. The 12z GFS and ECMWF are in gud agrmt and both indc gales ovr the ore and nrn cal wtrs as the sfc low crosses the wtrs. Prev solns did not agree as well as 12z runs...so confdc with the GFS/ECMWF solns is MDT attm...and with the gales. Wl go up to 40 kt with the wnds with this low.

The 12z mdls all indc the aforementioned shrtwv wl merge with the upr low...and slowly carve out a somewhat deeper h5 trof ovr the US grt basin. This is xpctd to enhance the assoc pres grad btwn the thrml trof and high pres W of the area...which is also xpctd to strengthen with the upr rdg drifting E. The prev fcst had gales ovr the srn zones as a result into Thu...and attm confdc is MDT with them due to fairly gud mdl agrmt...and gud run to run consistency...so xpct no major changes FM before. Also in question is the stg nrly grad ovr the pz5 wtrs in that time frame...as anthr low dvlps out of second cstl trof alng the Canadian coast and interacts with the same high W of the waters. The mdls agree fairly well on the stg pres grad...and the 12z NAM/GFS/Gem/ecwmf/UKMET all indc gales on Tue ngt into Wed ovr the N ptn...so wl add ot the fcst in this pkg. Otrw guid rmns in gud agrmt thrut the rmndr of the fcst pd...and preferring the 12z ECMWF for next fcst pkg.

Seas...plan to stay close to 12z ECMWF wave soln...in conjunction with the preferred wx mdl soln...with only minor modifications.

Extratropical storm surge guidance...N/A.

.Warnings/forecast confidence...Preliminary. Any changes will be coordinated through AWIPS 12 planet chat or by telephone:

.Pz5 Washington/Oregon waters... .Cape Flattery to Cape Lookout...gale Tue night and Wed...MDT confdc. .Cape Lookout to Pt St George...Gale Mon ngt into Tue...MDT confdc..then Tue ngt into Wed...low to MDT confdc.

.Pz6 California waters... .Pt St George to pt Arena...gale tonight into Mon...MDT confdc. Gale Tue into Wed...MDT confdc. .Pt Arena to pt Conception...Gale tonight into Mon gale Tue into Thu...MDT confdc. .Pt Conception to Guadalupe island...Gale Wed into Thu...MDT confdc. $$

.Forecaster kosier/Kells. Ocean prediction center.