Marine Weather for HS 102

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marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 739 PM PDT Sat Mar 25 2017

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

At 00z a high pressure ridge was across the pz5 and pz6 waters W/the exception of the far southeast CA waters where a cold front was located. Additionally a warm front was just west of the southwest pz5 waters. Will not make significant changes to the ongoing forecast in this intermediate update and allow current warning headlines in place to continue as is for now. Pre-frontal gales have continued to be suggested by the guidance ahead of the front anticipated to move through the waters overnight through late sun so confidence is medium to high there. In terms of additional warning headlines...chance of brief period fo gales Mon night into early Tue as a low pressure trough briefly strengthens along the CA coast before weakening. Beyond that normally am not one to put day 5 gales in the forecast but given 18z GFS along W/the 12z model package all were in good agreement in terms of developing gales in the northwest flow between inland troughing and the east Pacific high...will keep them in the forecast for now as well.

----------------------------------------------------------------- Previous discussion...

The satellite images still Show Low clouds covering most of the region with higher clouds over the central and northern waters. The lightning density map also shows very few strikes and mainly over the central waters. The sref model has prob 0 for severe tstms across the region and in the short term the model suggest only prob 5 for severe tstms over the eastern portion of the forecast waters adjacent to WA and or. The latest observations including scatterometer passes about 1810z show higher winds mainly over the far south-eastern waters at 20 kt close to the cold front.Elsewhere winds range between 5 and 15 kt with relatively lower winds over the central waters in the vicinity of the ridge axis. At 18z the NCEP map now has a weakening high pressure 1028 mb about 480 nm west of the far southern waters with its ridge extending northeast across the southern and central waters and a secondary center 1025 mb is farther west. A cold front stretches southwest across the far southern waters from inland low pressure over Southern California. Low pressure 987 mb near 50n150w has its front stretching southeast then continues southeast as a warm front about about 360 nm west of the north California waters. The pressure gradient is very slack across the region.

In the upper levels, the models GFS/CMC/ukmethr/ecmwfhr suggest an upper-level trough with some energy stretching south from the Gulf of AK along the Canada and US coastline. An upperlevel ridge is just behind the trough with very little energy. Farther west, the models suggest mainly zonal flow south of 35n with some significant energy embedded in upper level troughs north of 35n that will move into the north waters Sunday and will result in a tight pressure gradient and elevated winds over the northern waters.

The models GFS/CMC/ukmethr/ecmwfhr/NOGAPS/NAM/gfsmean have initialized well the 128 surface observations with just minor differences on the pressure field within 2 mb on the central pressure value for the high just west of the southern waters. There are also minor differences on wind speed within 5 kt. Otherwise, the models are still in a fairly decent agreement on the general synoptic pattern and sequence of features that will impact the region during the forecast period. In this issuance, there will be some changes mainly over the southern waters where warnings will be initiated and will tone down winds slightly over the waters adjacent to Oregon. Otherwise will continue to follow GFS closely for winds. In the short term, the high pressure west of the southern waters will weaken and dissipate as the secondary high pressure center farther west moves east. The cold front over the far southern waters will weaken as it moves southeast and dissipate. Low pressure will move toward the northern waters and pull a front across the region.

.Seas...The seas have peak at 12 ft over the Washington waters while they range between 6 and 10 ft over most of the region with relatively smaller seas over the southern waters. The wave models nww3 and ecmwfwave have matched the observed seas pattern very well and both models have been quite consistent in the previous runs. For this update will continue to stay close to nww3 wave model. The seas will build to 18 ft over the northern waters as cold front passes east.

.Extratropical storm surge guidance...N/A.

.Warnings...Preliminary.

.Pz5 Washington/Oregon waters... .pzz800...inner waters from Cape Flattery to Cape Shoalwater... gale Sunday. .Pzz900...Outer waters from Cape Flattery to Cape Shoalwater... gale tonight into Sunday. .Pzz805...Inner waters from Cape Shoalwater to Cape Lookout... gale Sunday. .Pzz905...Outer waters from Cape Shoalwater to Cape Lookout... gale tonight into Sunday. .Pzz810...Inner waters from Cape Lookout to Florence or... gale Sunday. .Pzz910...Outer waters from Cape Lookout to Florence or... gale tonight into Sunday. .Pzz815...Inner waters from Florence or to point St. George... gale Sunday. .Pzz915...Outer waters from Florence or to point St. George... gale tonight into Sunday.

.Pz6 California waters... .pzz835...inner waters from Point Piedras Blancas to Santa Cruz Island, CA... gale possible Thursday night. .Pzz840...Inner waters from Santa Cruz Island, CA to San Clemente Island, CA... gale possible Monday night. Gale possible Thursday night.

$$

.Forecaster Holley/musonda. Ocean prediction center.

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