

677 

AGPN40 KWNM 050230

MIMPAC



MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

730 PM PDT SUN SEP 4 2016



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

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



UPDATE...00Z OPC PRELIM SFC ANALYSIS SHOWS LOW PRES TROFING OVER

CALIFORNIA...WITH RIDGING ASSOCIATED WITH THE EPAC HIGH BUILDING E

TOWARD THE CONUS WEST COAST. LATEST AVAILABLE ASCAT HI-RES AND

ASCAT PASSES FROM LATE THIS AFTERNOON INDICATE AN AREA OF 25 TO 30

KT WINDS IN N TO NW FLOW OVER THE NRN AND CENTRAL CALIFORNIA

COASTAL AND INNER OFSHR WTRS...WITH A LARGER AREA OF WINDS TO 20

KT OVER THE SRN OREGON COASTAL WTRS MOST OF THE CALIFORNIA COASTAL

AND OFSHR WTRS.



MODELS...THE MED RNG MDLS ARE IN GUD OVERALL AGREEMNT ACROSS THE

OFSHR WTRS THRU THE FCST PERIOD...BUT THERE ARE SOME MINOR DIFFS

WITH THE STRENGTH OF THE PRES GRADIENT OVER THE NRN CALIFORNIA

OFSHR WTRS...WITH GFS 30M/GEM SHOWING 35 KT GALES AND

ECMWF/UKMET/GFS 10M INDICATING 30 KT WINDS. SINCE WE ALREADY HAVE

GALE WRNGS UP FOR THE INNER NRN CALIFORNIA OFSHR WTRS FOR THU AND

THU NITE...AM GOING TO KEEP THE GALES UP AT LEAST FOR NOW. ALL OF

THE MDLS ARE SHOWING GALES IN THE NRN CALIFORNIA COASTAL WTRS FOR

MUCH OF THE FCST PERIOD...INCLUDING THIS EVENING AND TONITE. WILL

CONTINUE TO USE A 50/50 BLEND OF GFS 30M/10M FOR THE WIND GRIDS

THRU THU...THEN WENT WITH THE REPRESENTATIVE UKMET FOR LATE THU

THRU FRI NITE.



SEAS...ENP WAVEWATCH III MDL AND ECMWF WAM BOTH LOOK REASONABLE

WITH THE SEA HTS THRU FRI NITE...AND ARE ALSO IN VERY GUD OVERALL

AGREEMNT. WILL USE THE ENP WAVEWATCH III MDL FOR THE WAVE HT

GRIDS THRU THE ENTIRE FCST PERIOD...EXCEPT AM GOING TO ADJUST

UPWARD 10 PERCENT FOR GALES LATER THU AND THU NITE.



EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



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

PREVIOUS DISCUSSION...



18Z NCEP SFC ANALYSIS SHOWS AN INLAND LOW PRES TROF EXTENDING

FROM INTERIOR SRN CA NW TO NRN CA COAST...WITH HI PRES CENTER WELL

W OF NRN CA EXTENDING A WK RIDGE NE INTO PZ5 AND NRN PZ6 WATERS.

HIGH RES ASCAT-A PASS FM 18Z RETURNED A SWATH OF NLY 20 TO 25 KT

OVR THE E PORTIONS OF CENTRAL AND NRN CA OFSHR WTRS AND ADJ CSTL

WATERS EXCP A SMALL AREA OF 30 KT VCNTY PT ARENA. 25-KT WINDS

EXTEND INTO SRN OREGON CSTL WTRS. LIGHTER WINDS ARE FOUND FARTHER

N AND S...EXCP BUOY OBS INDICATE WINDS TO 25 KT VCNTY AND S OF PT

CONCEPTION IN AREA MISSED BY ASCAT. LOW LVL STABILITY CONDS BEST

MODELED BY 12Z ECMWF SHOW WDSPRD NEUTRAL TO SOMEWHAT UNSTABLE LOW

LEVELS EXCP NEAR COAST OF CA WTRS WHERE IS COLD UPWELLING.

CHANNELING OF NLY WINDS ALG CST APPRS TO OFFSET THE MORE STABLE

CONDS NR COAST. A 50/50 BLEND OF THE 12Z GFS 10M AND HIGHER FIRST

SIGMA LVL WINDS APPEARS REPRESENTATIVE.



MAIN WEATHER FEATURES...RELATIVELY WEAK LOWS ARE EXPECTED TO

SLIDE OVER THE TOP OF THE EPAC RIDGE AND PASS SE ACROSS THE PZ5

WATERS FM LATE MON INTO TUE...THEN AGAIN WED INTO THU. OTHERWISE

THE CALIFORNIA TROF AND THE EPAC RIDGE WILL PREVAIL THRU THE FCST

PERIOD AND PRODUCE ROBUST N TO NW FLOW OVER THE NRN AND CENTRAL

CALIFORNIA OFSHR/COASTAL WTRS. THE EPAC RIDGE BREAKS DOWN MORE FRI

AND FRI NIGHT WHILE THE COASTAL TROF OVR CA REMAINS.



MODELS...THE 12Z MED RNG MDLS ARE IN VERY GOOD OVERALL AGREEMENT

ACROSS THE OFSHR/COASTL WTRS THRU THE FCST PERIOD...BUT SOME

SUBTLE DIFFERENCES DVLP OVR THE NRN WATERS AND NW INTO GLF OF AK

WHICH AFFECTS THE STRENGTH OF THE RIDGE NW OF CA WTRS. FOR THE

WIND GRIDS USED THER PREVIOUSLY MENTIONED BLEND OF 12Z GFS WINDS

THRU EARLY THU WHEN MDL AGRMT IS BEST. THE 12Z GEFS AND ECMWF

ENSEMBLE MEANS INDICATE 12Z GFS IS TOO FAST WITH A STRONGER LOW

MOVG ACRS GLF OF AK TWD SE AK LATER THU INTO FRI WITH 12Z ECMWF

SLOWEST. USED PREFERRED 12Z UKMET BL WINDS FOR LATER THU THRU FRI

NIGHT UNTIL LOW MOVS INLAND. WITH EVEN 10M WINDS OF UKMET SHOWING

GALE CONDS IN INNER NRN CA WTRS...SLGTLY HIGHER THAN OTHER MLDS

EXCP THE 12Z CMC GEM WHICH IS AGAIN OVERDONE WITH WINDS...PLAN TO

INITIATE GALES IN GRIDS FOR LATE THU AND THU NIGHT IN

PZZ820...WITH MDT CONFDC. 



SEAS...THE 12Z ENP WAVEWATCH III MDL AND THE 12Z ECMWF BOTH LOOK

REASONABLE WITH THE SEA HTS THRU FRI NIGHT...AND ARE ALSO IN VERY

GOOD OVERALL AGREEMNT. WILL USE THE 12Z ENP WAVEWATCH III MDL FOR

THE WAVE HT GRIDS THRU THE ENTIRE FCST PERIOD...EXCP ADD 10 PCT

DURING THE PERIOD OF GALES LATER THU AND THU 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 POSSIBLE THU INTO THU NIGHT. 



$$



.FORECASTER SCOVIL/BANCROFT. OCEAN PREDICTION CENTER.

