

209 

AGPN40 KWNM 181535

MIMPAC



MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

835 AM PDT THU AUG 18 2016



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

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



THE SAT IMG INDC STRONG HIGH PRES TO THE W OF THE NRN WATERS. ALL

THE OBSERVATIONS INCLUDING THE EARLIER ASCAT PASSES AT 0445Z AND

0626Z SHOW MAX WINDS OVER THE NRN WATERS AND WINDS HAVE DIMINISHED

TO BELOW GALE FORCE OVER THE CENTRAL WATERS BUT REMAIN IN THE GALE

FORCE THRESHOLD JUT N OF THE REGION. AT 12Z THE NCEP MAP HAS HIGH

PRES 1035 MB TO THE W OF THE REGION NEAR 45N140W AND ITS RIDGE

EXTENSION INTO THE WATERS. INLAND LOW PRES OVER CA HAS CONTINUED

TO MAINTAIN A TROF EXENDING NW INTO THE OR WATERS AND ANOTHER SE

ACROSS CA. ANOTHER TROF EXTENDS NW ACROS WA STATE. THE PRES

GRADIENT HAS RELAXED OVER THE CENTRAL WATERS BUT REMAINS TIGHT

JUST N OF THE REGION. THE SEAS PEAK AT 11 FT OVER THE CENTRAL

WATERS AND THEY RANGE BETWEEN 6 AND 9 FT ELSEWHERE. THE NWW3 MULTI

GRID WAVE MODEL IS VERY CLOSE TO THE OBSERVED SEAS PATTERN BUT

JUST UNDERDONE BY A FOOT OVER THE NRN AND CENTRAL WATERS.

OTHERWISE NWW3 AND THE ECMWFWAVE AGREE WELL IN THE SHORT TERM WITH

JUST MINOR DIFFERENCES WITHIN 1 FOOT IN THE EXTENDED PERIOD. THE

GLOBAL MODELS HAVE INITILAIZED WELL THE PRES FIELDS BUT HAVE SOME

MINOR DIFFERENCES IN THE WIND SPEED AND DIRECTION. THE GFS AND

UKMETHR MATCH THE OBSERVED WIND SPEED BUT ECMWFHR IS 5 KT BELOW

THE OBS OVER THE NRN AND CENTRAL WATERS WHILE THE CMC IS 5 KT

ABOVE THE OBS. SINCE THE ECMWHR IS CONSISTENTLY BELOW THE OBSERVED

WINDS SPEED AND THE CMC IS GENERALLY ABOVE...AM LEANING TWD GFS

AND THE UKMETHR. IN THE SHORT TERM THE HIGH PRES WILL PERSIST TO

THE W OF THE REGION WHILE THE INLAND TROF WEAKENS. THE PRES

GRDIENT WILL REMAIN RELAXED OVER THE REGION EXCEPT TO THE N AND SO

WILL BRIEFLY PUT GALES IN THE FAR NRN WATERS FOR JUST ONE PERIOD

BUT MAINATIN THEM JUST N OF THE REGION. 



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

PREVIOUS DISCUSSION...



THE ASCAT PASS FROM 05Z INDICATES MAINLY 25-30 KT ACROSS THE

WATERS N OF 35N WITH MAX WINDS TO 35 KT ACROSS THE COASTAL WATERS

ALONG THE NRN CA CST...JUST TOUCHING THE INNER OFFSHORE WATERS. S

OF 35 KT THE WINDS ARE RELATIVELY LIGHT. A NE-SW RIDGE AXIS IS

SITUATED JUST W OF THE OFFSHORE WATERS. RECENT OBS SHOW THE MAX

SEAS ARE NR 12-13 FT ALONG THE NR CA CST..SUBSIDING TO 4-6 FT OVER

THE SRN CA WATERS. FURTHER N OVER THE WA/OR WATERS SEAS ARE

RUNNING 6-10 FT.



OVER THE NEXT COUPLE OF DAYS THE RIDGE AXIS W OF THE REGION WILL

SLOWLY MOVE W CAUSING THE GRADIENT TO SLOWLY WEAKEN WHILE SHFTING

WESTWARD. THE WINDS OVER THE WA/OR WATERS WILL REMAIN STEADY AT

20-30 KT DURING THE FIRST 3 DAY...THEN GRADUALLY DIMINISH AS A

HIGH PRES RIDGE BUILDS E INTO THE WATERS. A LOW PRES TROUGH SW OF

VANCOUVER ISLAND WILL HELP MAINTAIN A TIGHTER GRADIENT ACROSS THE

NE PTN OF THE WA WATERS.



THE 00Z GLOBAL MODELS ARE IN PRETTY GOOD AGREEMENT THROUGHOUT THE

FORECAST PERIOD...ALTHOUGH THE GFS MAINTAINS A STRONGER GRADIENT

ALONG THE NRN CA CST LATER IN THE WEEK. THIS APPEARS A LITTLE

OVERDONE CONSIDERING BOTH THE ECMWF AND UKMET ARE WEAKER DURING

THAT TIME. WILL POP THE WIND GRIDS USING A 50/50 BLEND OF THE 10M

AND 30M GFS THROUGH 00Z SUN...THEN TRANSITION TO THE 10M GFS FOR

THE REMAINDER OF THE PERIOD. 



SEAS...BOTH THE ENP AND WAM WERE INITIALIZED PRETTY GOOD ACROSS

THE REGION. WILL POP THE WAVE GRIDS USING A BLEND OF THE ENP AND

WAM THROUGHOUT THE FCST PERIOD.



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





.WARNINGS...PRELIMINARY.



.PZ5 WASHINGTON/OREGON WATERS...

.PZZ900...OUTER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...

     GALE TONIGHT.



.PZ6 CALIFORNIA WATERS...

     NONE.



$$



.FORECASTER MUSONDA/SHAW. OCEAN PREDICTION CENTER.

