Marine Interpretation Message
Issued by NWS

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AGPN40 KWNM 300337
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
837 PM PDT FRI JUL 29 2016

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.

THE LAST MORNING ASCAT PASSES SHOWED LTL IN THE WAY OF GALE FORCE
WINDS OVR THE OFSHR AND CSTL WTRS...INSTEAD SHOWING NLY 20 TO 30
KT IN PZ5 WTRS AND A SOLID 25 TO 30 KT IN NRN CA WTRS. THESE CONDS
INDICATE CURRENT GRIDS BASED ON BLENDED GFS 10M AND 30M WINDS APPR
REPRESENTATIVE. SINCE THEN LATEST OBS INDICATE CONDS HAVE
INCREASED AS A SML CAA SURGE WORKS ITS WAY S INTO PZ5 WTRS
INCREASING THE CHANCE GALE FORCE WINDS WILL MIX DOWN. IN FACT
SHIP REPORTS WITH 35 KT APPR OFF VANCOUVER ISL AND OFF PT ST
GEORGE IN CSTL WTRS AT 00Z...AS THE INLAND THERMAL LOW PRES TROF
STRENGTHENS DIURNALLY. AS COLD SURGE CONTS TO MOV S AND AN UPR
SHRTWV TROF MOVS INLAND N OF AREA SHRTWV UPR RDG BLDS IN BEHIND IT
AND INCREASES GRADIENT IN NRN WTRS BETWEEN A TROF NR VANCOUVER ISL
AND AND SFC RDG BLDG FM W. LATEST MDLS SPRT EXPANSION OF GALES
TONIGHT INTO SAT NIGHT BOTH FM DIURNAL EFFCTS AND RDG BLDG FM W
WITH PSBL EXPANSION OF GALE OFF NRN CA INTO ADJ OUTER ZONE BUT
CONT TO HAVE HIGH CONFDC IN GALES FOR INNER ZONES OFF WA AND ALSO
SRN OREGON AND NRN CA.

AN UPR CLOSED LOW IS FCST BY MDLS TO APCH NRN WTRS FM WNW SAT
NIGHT INTO SUN NIGHT WHICH WILL WKN THE OFSHR HIGH PRES RDG FIRST
IN THE NRN WTRS SAT NIGHT...ENDING THE GALES THERE...AND THEN THE
CENTRAL PORTIONS INCUDING OREGON AND NRN CA SUN AND SUN NIGHT. UPR
AND SFC RDG REBUILD EWD AFTER UPR LOW MOVS INLAND MON NIGHT INTO
TUE. THIS WL LKLY INCREASE GRADIENT ENUF TO REDVLP NLY GALES AT
LEAST OVR NRN CA INNER WTRS TUE NIGHT INTO WED NIGHT.

FOR THE EVENING UPDATE THE CURRENT FCST GRIDS LOOK RSNBL ALG WITH
ASCD WAVE GRIDS BASED ON CONSISTENT AND REPRESENTATIVE GFS AND ENP
WW3 GUIDANCE...WITH 12Z ECMWF WAVE GUIDANCE SIMILAR.
-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE SAT IMG INDC FAIRLY CLOUDY SKIES ACROSS THE REGION BUT ALMOST
NO REPORTS OF LIGHTNING STRIKES. ALL THE OBSERVATIONS INDC HIGHER
WINDS OVER THE NRN CAL AND SRN OREG WATERS. AT 18Z INLAND TROF
EXTENDS NW FROM LOW PRES OVER SRN CAL INTO THE SRN OREG. HIGH PRES
1034 MB W OF THE WATERS NR 42N145W HAS ITS RIDGE OVER MOST OF THE
REGION. THE PRES GRADIENT IS TIGHT OVER THE NRN CAL AND SRN OREG
WATERS BUT QUITE SLACK ELSEWHERE.

MOST OF THE ENERGY IS JUST E OF AN UPPERLEVEL HIGH PRES CENTERED
NR 40N140W. THERE IS ANOTHER UPPERLEVEL HIGH PRES INLAND OVER THE
S-WRN STATES. THE TWO AREAS OF HIGH PRES HAVE CAUSED A SLOW DOWN
ON THE MOVEMENT OF OTHER SYNOP FEATURES. MOST OF THE ENERGY WILL
CONTINUE TO LINGER AROUND THE CNTRAL WATERS AND THAT WILL MAINTAIN
THE CURRENT SYNOPTIC FEATURES PATTERN. AS THE ENERGY SLOWLY SHIFTS
E OF THE WATERS IN THE EXTENDED PERIOD...AN UPPERLEVEL HIGH WILL
MOVE E INTO THE WATERS AND THAT WILL FORCE A RELAXED PRES GRADIENT
AND ALLOW WINDS TO DIMINISH BELOW GALE WARNING THRESHOLD.

THE GLOBAL MODELS HAVE INITIALIZED VERY WELL AND THEY ARE IN
GENERALLY A GOOD AGREEMENT ON THE FEW SYNOP FEATURES THAT ARE
CONTROLLING THE WX OVER THE REGION. WILL UPDATE THE FORECAST
WITHOUT MAJOR CHNAGES TO THE PREVIOUS FORECAST AND WILL STAY WITH
JUST GFS. IN THE SHORT TERM HGH PRES WILL REMAIN TO THE W AS
INLAND TROF PERSITS OVER CAL. THE WINDS WILL REMAIN ELEVATED IN
THE SHORT TERM BUT WILL DIMINISH TO BELOW GALE FORCE IN THE
EXTENDED PERIOD.

.SEAS...THE SEAS PEAK AT 12 FT OVER THE CENTRAL REGION AND THEY
RANGE BETWEEN 4 AND 7 OVER THE FAR SRN AND NRN WATERS. THE JASON
SWATHS AT 1712Z AND 1915Z MISSED THE CENTRAL WATERS BUT INDC SEAS
TO 5 FT OVER THE FAR NRN AND FAR SRN WATERS. THE NWW3 MULTI GRID
WAVE MODEL FITS FAIRLY WELL WITH THE OBSERVED SEAS PATTERN AND HAS
BEEN VERY CONSSISTENT. WILL STAY WITH ENP. IN THE SHORT TERM THE
SEAS WILL REMAIN LARGE OVER THE CENTRAL WATERS WITH PEAKS TO 15 FT
WHILE SEAS WILL JUST SUBSIDE IN THE EXTENDED PERIOD TO PEAKS AT 13
FT.

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

.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
.PZZ800...INNER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE TONIGHT INTO SAT NIGHT.
.PZZ900...OUTER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE TONIGHT.
.PZZ815...INNER WATERS FROM FLORENCE OR TO POINT ST. GEORGE...
     GALE TONIGHT INTO SUN.

.PZ6 CALIFORNIA WATERS...
.PZZ820...INNER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE TONIGHT INTO SUN.
     GALE POSSIBLE SUN NIGHT.
     GALE POSSIBLE TUE NIGHT INTO WED NIGHT.
.PZZ920...OUTER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE SAT.

$$

.FORECASTER BANCROFT/MUSONDA. OCEAN PREDICTION CENTER.



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