

327 

AGPN40 KWNM 070336

MIMPAC



MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

836 PM PDT SAT AUG 6 2016



.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT

.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.



A 1034 MB HIGH PRES CENTER REMAINS STATIONED WELL OFFSHORE NEAR

45N145W PER THE 00Z OPC SFC ANALYSIS. GOES15 W/V IMAGERY SHOWS A

WELL DEFINED MID/UPR LVL LOW ENTERING THE FAR NE PZ5 WTRS AFTER

PASSING OVR VANCOUVER ISL. ALTHOUGH NOT SHOWN IN SFC ANALYSIS

MOST GLOBAL MDLS AND NAM INDIATE A WK SFC REFLECTION CO-LOCATED

WITH THE UPR LOW. AS A RESULT THE PRES GRADIENT CONTINUES TO

RELAX ALONG THE W COAST AS THIS UPR LOW...AS WELL AS A SHORTWAVE

TROF OVER THE OUTER PZ6 WTRS...HELP TO WEAKEN THE INFLUENCE OF THE

OFFSHORE RIDGE. EARLIER ASCAT PASSES INDICATED WIND SPEEDS HAVE

DIMINISHED TO 15-25 KT ACROSS THE OFFSHORE WTRS WITH HIGHEST CONDS

SHIFTED OUT OF PZ5 WTRS AND INTO PZ6 WTRS...MAINLY CAPE MENDOCINO

SWD...AND THE MODELS AGREE THAT THIS TREND WILL CONTINUE THRU

TONIGHT. AFTER TONIGHT MODEL DIFFERENCES ARE MINOR WITH SOME SPRT

FOR A PERIOD OF GALES OFF NRN AND CENTRAL CA COAST TUE AS THE EPAC

UPR AND SFC RIDGES BUILD BACK EWD. THEREFORE...NO NOTABLE CHANGES

TO THE FCST PACKAGE THIS EVENING.

-----------------------------------------------------------------

PREVIOUS DISCUSSION...



THE 18Z OPC SFC ANALYSIS INDICATES A WEAK 1014 MB LOW HAS MOVED

INTO THE NE WA OFFSHORE WTRS THIS AFTN...WHILE ITS ASSOCIATED UPR

LOW REMAINS OVER VANCOUVER ISLAND ACCORDING TO THE LATEST WV SAT

IMAGERY. THE WV CHANNEL ALSO REVEALS A SHORTWAVE TROF IS MOVING

ACROSS THE CENTRAL PZ6 WATERS. BOTH OF THESE UPR FEATURES HAVE

WEAKENED THE RIDGE ALOFT AND CONTRIBUTED TO A RELAXING OF THE

PRES GRADIENT ALONG THE W COAST. HI RES ASCAT-A/B PASSES AT

1752Z/1845Z REVEALED A SWATH OF 15-25 KT NLY WINDS OVER THE

NRN/CENTRAL CA OFFSHORE AND COASTAL ZONES. WINDS ARE MUCH WEAKER

OVER THE INNER PZ5 WTRS...GENERALLY 10 KT OR LESS. A 1034 MB SFC

HIGH REMAINS WELL OFFSHORE NEAR 45N145W THIS AFTN.



THE 12Z GFS/ECMWF/UKMET REMAIN IN VERY GOOD AGREEMENT THRU THE

FCST PERIOD. AS THE UPR LOW NEAR VANCOUVER ISLAND MOVES INLAND

OVER WA SUN THRU MON...THE UPR RIDGE EXPANDS EASTWARD AND SFC HIGH

PRES MOVES SE TO AROUND 42N142W. A SFC RIDGE AXIS WILL DROP S

ACROSS THE PZ5 WTRS ON MON...ACCOMPANIED BY A NLY SURGE ACROSS THE

OUTER PZ5 WTRS WITH WINDS INCREASING TO 15-25 KT. THE SFC GRADIENT

TIGHTENS OFF THE CA COAST MON INTO TUE AS A THERMAL TROF SHARPENS

OVER CA. BY 12Z TUE...COULD POTENTIALLY SEE GALES DEVELOP OVER THE

NRN CA COASTAL AND INNER OFFSHORE WTRS. THE PAST FEW GFS RUNS HAVE

CONSISTENTLY GENERATED GALES OVER THE COASTAL WTRS RIGHT UP TO

THE INTERFACE OF OUR OFFSHORE ZONES...AND EVEN THE 12Z ECMWF SHOWS

A SWATH OF 30 KT IN THIS AREA. THEREFORE...FEEL COMFORTABLE

MAINTAINING A SMALL AREA OF GALES OVER INNER PORTIONS OF PZZ820

AND PZZ825 ON TUE. THEN SFC HIGH PRES MOVES NW AWAY FROM THE WTRS

BY MID WEEK...ALLOWING THE GRADIENT TO RELAX AGAIN WED THRU THU.



THE 12Z GFS 10M WINDS WERE THE PREFERRED MODEL CHOICE FOR TODAYS

FCST...EXCEPT ON TUE WHEN A 50/50 30M/10M BLEND WAS USED TO KEEP

GALES OVER THE INNER NRN CA WTRS.



.SEAS...BASED ON THE 18Z SEA STATE ANALYSIS...THE 12Z ECMWF WAM

SEEMS TO HAVE INITIALIZED BETTER THAN THE 12Z NWW3. THEREFORE USED

THE WAM TONIGHT THRU SUN...THEN TRANSITIONED TO THE 12Z NWW3 SUN

NIGHT THRU THU NIGHT. THE NWW3 WAS PREFERRED LATER IN THE FCST

PERIOD AS IT GENERATED HIGHER SEAS ON TUE WITH THE ANTICIPATED

GALES OFF NRN CA.



.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



.WARNINGS...PRELIMINARY.



.PZ5 WASHINGTON/OREGON WATERS...

     NONE.



.PZ6 CALIFORNIA WATERS...

.PZZ820...INNER WATERS FROM POINT ST. GEORGE TO POINT ARENA...

     GALE POSSIBLE TUE.

.PZZ825...INNER WATERS FROM POINT ARENA TO PIGEON POINT...

     GALE POSSIBLE TUE.



$$



.FORECASTER BANCROFT/REINHART. OCEAN PREDICTION CENTER.

