Marine Interpretation Message
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000
AGPN40 KWNM 010310
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
810 PM PDT MON AUG 31 2015

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

THE SAT IMG INDC MSTLY CLR SKIES OVR THE SRN HALF BUT CLDY OVR
THE NRN WTRS WITH NO LIGHTNG STRIKES. THE RADAR HAS NO INDC OF
TSTMS CELLS OVR THE ENTIRE REGION. AT 00Z WEAK INLAND LOW PRES
1000 MB OVR CANADA JUST N OF WA STATE HAS A CLD FRNT STRTCHNG SW
ACRS WA THEN INTO THE NRN WTRS HENCE THE CLDY NRN WTRS. HGH PRES
1030 MB NR 42N155W HAS ITS RIDGE RIDGE XTNDG SE ACRS THE SRN WTRS
WITH ITS RIDGE AXIS PASSING JUST W OF THE SRN WTRS. INLAND LOW
PRES TROF STRETCHES FROM SRN CA INTO SRN NV. THERE IS ANOTHER LOW
PRES 992 MB OVR THE ERN PARTS OF THE GULF OF AK THAT HAS A TROF
STRCHNG SE ALONG THE CANADA COAST. THE PRES GRDNT IS JUST TIGHT
OVR THE NRN WTRS ESPCLY WITHIN THE VCNTY OF THE CLD FRNT. THE MAX
OBSVD WINDS ARE 25 KT OVR THE NRN WTRS AND THEY RANGE BTWN 10 AND
20 KT ELSEWHERE. THE LAST ASCAT PASS OVR THE REGION WAS AT 1845Z
BUT IT MISSED THE NRN WTRS AND JUST HAD WINDS TO 20 KT OVR THE ERN
PARTS OF THE CNTRL REGION. THE ASCAT HAD GALE FORCE WINDS IN AREA
BEYOND 240 NM NW OF THE REGION. THE SEAS ARE EQUALLY SMALL WITH 11
FT BEING HGHST OVR THE FAR SRN WTRS MAINLY DUE TO LARGE PRD SWELL
FROM THE TC SYSTEMS TO THE SW. OTHERWISE SEAS RANGE BTWN 7 AND 10
FT ELSEWHERE. BOTH THE NWW3 MULTI GRID AND THE ECMWFWV MDLS ARE
VERY CLOSE TO THE OBSVD SEAS PATTERN AND THEY HV BEEN QUITE
CONSSTNT IN THE PREVIOUS RUNS. EVEN A BLEDN OF 50/50 DOES NOT
YIELD ANY VIVID CHNGS AND SO WILL JUST STICK TO THE NWW3 MULTI
GRID WV MDL THRU OUT THE FCST PRD.

MOST OF THE ERNGY IS CONFINED TO THE N OF THE REGION IN AN
UPPRLVL TROF THAT HAS ITS SHALLOW TROF AXIS XTNDG TO JUST W OF THE
SRN WTRS. AN UPPRVL RIDGE IS FARTHER W OVR THE CNTRL PAC. THE
ENRGY TO THE N WILL SLOWLY SHIFT SE AND ENTER THE NRN HALF OF THE
REGION. THIS SENARIO SHUD BE ABLE TO STRENGTHEN THE SFC FEATURES
AND EVEN TIGHTEN THE PRES GRDNT. HOWEVER THE PAC HAS TO BALANCE
ITS ENRGY WITH OTHER SYS TO THE S AND ALSO THE INLAND RIDGE WILL
BE WEAK. THIS COMBINATION WILL STILL MAINATIN A TROF ACRS THE WTRS
BUT RELATIVELY DRY AND NOT TIGHT ENOUGH TO GENERATE GALE FORCE
WINDS. UPPRLVL RIDGE WILL START TO SHIFT E AS THE TROF MOVES
INLAND IN THE XTNDD PRD AND THAT WILL RELAX THE PRES GRDNT AND
WINDS WILL SLIGTHLY DIMINSH. A MDL CHOICE SHUD THERFORE BE ONE
THAT WILL NOT HV GALE FORCE WINDS IN THE FRCST AND MUST SHOW
ENHANCED WINDS IN THE SHORT TERM BUT DIMINISHING IN THE XTNDD PRD.

THE GLBL MDLS HV INITIALIZED FAIRLY WELL AND THEY ARE IN GENERAL
AGRMNT IN THE SHORT ERM WITH JUST MNR DIFFS MAINLY OVR THE TRACK
OF THE LOW IN THE GULF OF AK AS IT APPROACHES THE NRN WTRS. ONLY
UKMET KEEPS THE LOW STILL OVR THE WTRS WED. ANOTHER MNR DIFFS IS
THAT MOST OF THE MDLS JUST MAINTAIN A TROF ALONG THE CANADA COAST
WHILE GFS SLIGHTLY DEEPENS TO TRY AND HAVE CLOSED LOW WHICH ALLOWS
ENHANCED WINDS. THE CMC WEAKENS ITS HGH PRES TO THE W WHICH
IMPLIES WEAKER WINDS. ALL THE MDLS JOIN GFS AND AGREE ON CLOSED
LOW BY THU. OTHERWISE THERE ARE REALLY MNR DIFFS IN THE MAIN SYNOP
PIC AND SO WILL USE THE LEADING MDL GFS WITH MNR ADJ IN THE GRIDS.
IN THE SHORT TERM THE HGH PRES OVR THE CNTRL PAC WILL REMAIN IN TE
SMAE VCNTY AND ABOUT THE SAME STRENGTH AND WILL MAINTAIN ITS SE
RIDGE IMPCAT OVR THE SRN AND CNTRL WTRS. THE CLD FRNT WILL SLOWLY
MOVE SE ACRS THE NRN WTRS AND THEN WEAKEN AND FINALLY DSIPT OVR
THE CNTRL WTRS. LOW PRES IN THE GULF OF AK WILL MOVE SE TO PASS
OVR THE ERN PARTS OF THE NRN WTRS THEN DSIPT IN THE XTNDD PRD. THE
WINDS WILL REMAIN BELOW GALE FORCE THRU THE FCST PRD.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE 18Z NCEP FINAL SFC ANALYSIS SHOWS A STRONG 1029 MB HIGH PRES
AREA WELL TO THE W OF THE OFSHR WTRS NR 42N158W WHICH HAS BEEN
DRFTG E. A COLD FRONT IS MOVG SE INTO NW WA OFSHR WTRS. THE FRONT
IS FCST TO MOVE SE AND REACH THE OREGON WTRS EARLY TONIGHT...AND
NRN CA WTRS BY LATER TUE. LOW PRES OVR THE NERN GULF OF AK WILL
TRACK SE TOWARD THE OFSHR WTRS THRU TUE WHILE WEAKENING. NW GALES
ARE OCCURRING OVR THE WRN GULF OF AK PER THE LATEST OBS. THE GALES
ARE FCST TO REMAIN TO THE NW OF THE OFSHR WTRS THRU TUE NITE AS
THE LOW SLIDES SE AND APPROACHES PZ5 WTRS FROM THE NW WHILE WKNG.
THE 12Z MDL GUID IS IN DECENT AGRMT OVR THE REGION THRU WED. WE
WILL REMAIN CLOSE TO THE 10M GFS WINDS FOR THE AFTERNOON FCST
PACKAGE THRU WED NIGHT EXCP BOOSTED WNDS IN PZ5 WTRS BY 10 PCT TUE
AND TUE NIGHT AS GFS DVLPS MRGL UNSTABLE LOW LVLS IN CAA BHND
CDFNT. WNDS MAY BRFLY REACH AS HIGH AS 30 KT IN NW WA WTRS TUE AS
A RESULT...AND IT APPEARS THAT GALES SHOULD REMAIN NW OF THESE
WTRS.

THE LOW MENTIONED ABV IS FCST TO DSIPT N OF THE WTRS EARLY WED AS
THE STRONG HIGH BEGINS TO BUILD E. A COASTAL LOW PRES TROF WILL
DEVELOP AND INTENSIFY LATER WED THRU THU NGT ESPEC FROM THE FAR
SRN OREG COAST S TO CENTRAL CALIF. THE HIGH WILL CONT TO SLOLY BUILD
OVR THE E PAC WED THRU THU NITE AND APPROACH 44N142W BY EARLY FRI
MORNING. THERE WILL BE AN INCREASING CHANCE FOR GALES OFF THE
NOCAL COAST BY LTR THU AND THU NITE AS A RESULT OF THE
STRENGTHING PRES GRAD OVR THE REGION. HOWEVER THIS INCREASE IN
GRADIENT MAY BE TEMPERED BY DVLPMT OF WK LOW PRES N OF THE WTRS
THU WHICH MDLS ESPCLY 12Z GEM AND UKMET MORE AGGRESSIVELY MOVE SSE
INTO PZ5 WTRS THU NIGHT INTO FRI BEFORE DSIPG ONSHORE LATER FRI.
AS A RESULT THOSE MDLS APPR TO BACK OFF ON SPRT OF GALES AT LEAST
IN CSTL WTRS LATER IN WEEK SO AS A RESULT PLAN TO TRANSITION FROM
12Z GFS TO A 50/50 BLEND OF GFS AND ECMWF FOR THU AND BYND WHICH
WILL GIVE HIGHEST WNDS 30 KT OFF CENTRAL CA CST AT TIMES LATER THU
THRU SAT NIGHT AND 20 TO 25 KT ELSW FM SE OREGON WTRS SWD.

SEAS...SEA HTS OVR THE OFF WTRS PER THE LATEST OBS AND ALTIMETER
PASSES ARE RUNNING GENERALLY WITHIN A FT OR TWO OF THE 12Z ENP
WAVE WATCH III MDL OUTPUT. AS WE ARE USING THE 12Z GFS WINDS FOR
THE OFF WTRS FCST FOR TODAY THRU WED NIGHT WE WILL STAY CLOSE TO
THE ENP WW3 MDL GUID. FOR THU AND BYND AS WE USE A 50-50 BLEND OF
THE GFS AND ECMWF MDLS FOR WINDS...WE WILL USE A 50-50 BLEND OF
THE ENP WW3 AND ECMWF WAM FOR SEA HTS. OVERALL...NO MAJOR CHANGES
ARE ANTICIPATED FOR THE AFTERNOON PACKAGE FROM THE PAST FEW OPC
FCSTS.

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


.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
     NONE.

.PZ6 CALIFORNIA WATERS...
     NONE.

$$

.FORECASTER MUSONDA/BANCROFT. OCEAN PREDICTION CENTER.


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