

698 

AGPN40 KWNM 021456

MIMPAC



MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

756 AM PDT TUE AUG 2 2016



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

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



THE 12Z OPC SFC ANALYSIS SHOWS AN ENHANCED PRES GRADIENT OFF THE

NRN CA/SRN OR COAST BETWEEN A 1036 MB HIGH NEAR 45N146W AND A WEAK

THERMAL TROUGH INLAND OVER CA. IN ADDITION...A WEAK 1017 MB LOW

JUST N OF THE WA WATERS IS MOVING SE TOWARD THE WA COAST. THE

STRONGEST WINDS OVER THE FCST AREA REMAIN CONCENTRATED OFF THE NRN

CA COAST...GENERALLY 20-30 KT AND HIGHEST OVER THE COASTAL WATERS.



ONLY MINOR CHANGES TO THE NEAR TERM GRIDS WITH THIS MORNING

UPDATE. BASED ON A 0901Z RSCAT PASS OVER THE NRN CA WATERS...HAVE

DECIDED TO USE THE 10M GFS WINDS TODAY SINCE THESE APPEAR TO BE

MORE REPRESENTATIVE THAN THE 30M GFS WINDS. HAVE ALSO ADDED SCT

SHOWERS ACROSS THE NRN PZ5 WATERS IN ASSOCIATION WITH THE

AFOREMENTIONED LOW. OTHERWISE THE PREVIOUS FCST REMAINS ON TRACK.



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

PREVIOUS DISCUSSION...



AT 06Z THE NCEP SFC ANALYSIS SHOWED A SURFACE TROF OVER THE WA

WATERS WHILE A WEAK THERMAL TROF WAS OVER INLAND CA AND STRONG

HIGH PRES REMAINED STNRY NEAR 45N 148W. LATEST MODELS ARE IN

GOOD AGREEMENT THAT THE LOW PRES TROF AS A SFC REFLECTION OF AN

ASCD MID/UPPER LEVEL LOW WILL MOV ONSHORE OVR WA TODAY INTO EARLY

TONIGHT. 0430Z AND 0610Z HIGH RES ASCAT-B PASSES RETURNED WINDS

RANGING FM 10 KT NE WA WTRS TO 20 TO 30 KT OVER THE NW HALF OF THE

CA WATERS...WITH THE 30 KT OCCURRING AT PASS EDGE W OF PT ARENA ON

EDGE OF DATA FREE SWATH. SLGTLY EARLIER RAPIDSCAT PASSES FM 0230Z

AND 0410Z REVEALED WINDS HAVE LOWERED TO SUBGALE NEAR PT ST GEORGE

WHERE EARLIER THERE WERE SUSPECTED GALES. THEREFORE NEW FCST WILL

START WITH HIGHEST WINDS TO 30 KT ACROSS COASTAL ZONES FROM CAPE

BLANCO TO PT ST GEORGE AND PERHAPS INTO ADJ INNER OFSHR ZONES W OF

PT ARENA AS PER ASCAT IMAGERY. THE 00Z GFS WINDS LOOK WELL

INITIALIZED ACROSS THE COASTAL AND OFSHR AREAS AND FOR THE NEW

FCST WE WL START WITH REPRESENTATIVE GFS 30M WINDS.



THE 00Z MODELS ARE IN GOOD AGREEMENT THAT HIGH PRES CENTERED NEAR

45N148W AT 06Z WILL DRIFT E WHILE STRENGTHENING OVER THE NEXT 24

TO 36 HOURS AND THEN PERSIST INTO THE WEEKEND. OVER THE PAST FEW

RUNS THE MODELS HAVE GENERALLY TRENDED A BIT WEAKER WITH THE N

WINDS FROM CAPE BLANCO TO PT ARENA THIS WEEK. THE 00Z GFS LIKE

PREVIOUS TWO RUNS DOES NOT SHOW ANY GALE FORCE WINDS EXTENDING

BEYOND 60 NM INTO OFFSHORE WATERS EVEN WITH THE HIGHER FIRST SIGMA

LAYER OR 30M WINDS. FOR CONTINUITY HAVE MAINTAINED PREVIOUS GALE

WARNINGS WITH ONLY MINOR DIFFERENCES IN TEMPORAL COVERAGE BASED ON

USE OF A BLEND OF THE 00Z GFS 10M AND 30M WINDS WITH HIGHER

CONTRIBUTION OF 75 PCT FROM THE 30M WINDS AFTER INITIALLY USING

100 PCT 30M WINDS FOR FIRST PERIOD. ONLY HAVE MODERATE CONFIDENCE

WITH THESE GALES BUT HIGHER CONFIDENCE IN GALES AFFECTING ADJ CSTL

ZONES. MDLS AGREE ON WKNG GRADIENTS BY FRI AS ANOTHER UPR LOW AND

SFC TROF DROP SE INTO PZ5 WTRS SUPPRESSING SFC RDG IN OFSHR WTRS

AND ENDING GAES IN OFSHR WTRS BY THEN.



THE 00Z ECMWF WAM APPRS TO HAVE BEST INITIALIZATION COMPARED TO

06Z SEA STATE ANALYSIS TO START NEW FCST. OPC WAVE HEIGHT GRIDS

ARE LARGELY BASED ON THE 00Z ECMWF WAM TODAY AND 00Z ENP WW3 AFTER

THAT...HOWEVER GRIDS WERE ADJUSTED UPWARD BY ABOUT 10 PERCENT

ACROSS AREAS WITH WINDS GREATER THAN 25 KT AND/OR SEAS GREATER

THAN 9 FT OFF NRN CALIFORNIA THROUGH SAT NIGHT.



.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 WED INTO WED NIGHT. 

     GALE POSSIBLE THU INTO THU NIGHT. 



$$



.FORECASTER REINHART/BANCROFT. OCEAN PREDICTION CENTER.

