Marine Interpretation Message
Issued by NWS

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000
AGPN40 KWNM 210256
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
756 PM PDT MON APR 20 2015

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

SAT IMG HAS INDC SOME CLDS OVR THE REGON BUT NO LIGHTNG ABD THE
RADAR HAS NO TSTMS CELLS OVR THE REGION. AT 0000Z THE MAIN SYNOP
FEATURE IS HGH PRES 1032 MB CNTRD NR 40N150W WHICH HAS TS RIDGE
XTNDG INTO MOST OF THE REGION. LOW PRES 1008 MB 360 NM N OF THE
WTRS HAS A CLD FRNT STRCHNG S INTO THE NW PARTS OF THE WASH WTRS.
THERE IS A SERIES LOW PRES CNTRS ALONG AN INLAND TROF THAT
STRETCHES FROM SRN CA THRU NRN CAL INTO OREG AND WASH STATES. THE
PRES GRDNT IS SLCK AT THE MOM OVR THE REGION BUT IS BECOMING TIGHT
OVR THE CNTRL WTRS NR THE REGION WHERE THE TROF IS DEEPER. THE
OBSVD WINDS ARE HGHR OVR THE CNTRL WTRS REACHING 25 KT BUT THEY
RANGE BTWN 10 AND 20 KT ELSEWHERE. THE LAST R-SCAT PASS AT 1938Z
HAD NO WINDS ABOVE 20 KT OVR THE REGION. THE SEAS RANGE BTWN 6 AND
10 FTA ACRS THE REGION WITH RELTVLY HGHR SEAS OVR THE CNTRL WTRS.
THE NWW3 MULTI GRID THO FITS WELL WITH THE OBSVD SEAS PATTERB HAS
BEEN UNDERDONE BY A FOOT OVR THE REGION. OTHERWISE NWW3 IS VERY
CLOSE TO THE ECMWFWAVE AND HAS BEEN QUITE CONSSTNT.

AN UPPRLRVL RIDGE IS JUST E OF THE NRN WTRS WHILE A BROAD UPPRLVL
TROF LIES JUST W OF THE SRN WTRS WITH SOME LOCALLY INDCD ENRGY.
ANOTHER BUCH OF ENRGY IS EMBDD IN AN UPPRLVL TROF THAT XTNDS SE
FROM THE GULF OF AK THEN TURNS SW NR 50N140W. UPSTREAM ARE POCKETS
OF ENRGY IN A TROF OVR CNTRL PAC NR THE DATELINE BTWN 30N AND 65N.
IN THE HSORT TERM THE ENERGY IN THE GULF OF AK WILL DROP DOWN TO
RE ENFORCE THE ENERGY OVR THE CNTRL WTRS. AN UPRLVL RIDGE WILL
FORLLOW BEHIND THE TROF IN THE XTNDD PRD. AS SUCH THE PRES GRDNT
OVR THE REGION MUST BECOME TIGHTER AND WINDS WILL BE ELEVATED TO
GALE FORCE BUT SHUD REMAIN BELOW GALE FORCE IN THE XTNDD PRD.

THE 1800Z MDL RUN CONTINUES TO SHOW AGRMNT AMONG THE MDLS ON THE
HGH PRES AND THE INLAND TROF. MDLS HAV INTIALIZED WELL AND FOR
THIS UPADATE WILL NOT DEVIATE FROM THE PREVIOUS FORECAST AND SO
WILL STAY WITH GFS FOR MOST OF THE FRCST PRD. IN THE SHORT TERM
THE HGH PRES WILL MOVE E AS IT BUILDS WHILE THE INLAND TROF WILL
DEEPEN FARTHER AND THAT WILL TIGHTEN THE PRES GRDNT OVR THE REGION
TO GENERTATE GALE FORCE WINDS. LOW PRES WILL THENNPASS N OF THE
REGION AND FORCE THE HGH PTES TO RETREAT SW AMD THAT WILL REALX
THE PRES GRDNT THAT WILL RESULT IN THE DIMINISHING OF GALE FORCE
WINDS.

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

THE 18Z SFC ANALYSIS INDICATED A COLD FRONT NEARING THE WA/OR
OFFSHORE WATERS WITH WEAK TROUGH INLAND OVER CA.

THE 12Z MODELS ARE IN VERY GOOD AGREEMENT THROUGH THE MAJORITY OF
FCST PERIOD FROM TONIGHT THROUGH ABOUT 00Z SAT. THE MAIN FCST
CONCERN CONTINUES TO BE DURING THE SHORT TERM PERIOD BEGINNING TUE
AFTERNOON AND CONTINUING INTO THU MORNING. THE MODELS ALL CONTINUE
TO INDICATE HIGH PRES RIDGE BUILDING E OVER THE E PAC WHILE TROUGH
STRENGTHENS ALONG THE CA COAST. THIS WILL LEAD TO INCREASING N TO
NW WINDS OVER THE N/CENTRAL CA AND FAR SRN OR OFFSHORE/COASTAL
WATERS BEGINNING TUE MORNING AND CONTINUING INTO THU. WILL NOT
MAKE ANY DRASTIC CHANGES TO EXISTING WARNING HEADLINES AS FCST
CONFDC IS HIGH CONSIDERING THE VERY GOOD MODEL AGREEMENT. THE
COASTAL TROUGH WILL THEN WEAKEN LATER THU INTO EARLY FRI WITH
WINDS DROPPING BELOW GALE. WILL ALSO CARRY A PERIOD OF GALES
OVER THE INNER PORTION OF NRN WA OFFSHROE WATERS TUE NIGHT INTO
EARLY WED AS TROUGH MOVES ACROSS THE AREA. THE 12Z GFS HAS
TRENDED WEAKER WITH LOW PRES FCST TO PASS N OF THE WA WATERS THU
NIGHT INTO EARLY FRI...AND IN FACT THE NEW GFS MATCHES UP WELL
WITH THE ECMWF/UKMET/GEM. LOOKING AHEAD TO LATE FRI INTO SAT
NIGHT...THE MODELS ALL INDICATE ANOTHER LOW PASSING NW OF THE
WA/OR WATERS. THE GFS APPEARS TO BE A STRONG OUTLIER WITH THE
LOW...WHILE THE UKMET/ECMWF ARE IN BETTER AGREEMENT. WILL PLAN
ON LEANING MORE TOWARD THE ECMWF/UKMET DURING THIS TIME PERIOD.
IN SUMMARY...WILL POPULATE WINDS GRIDS USING THE GFS 10M WINDS
THROUGH 21Z TUE. FROM 00Z WED THROUGH 03Z FRI WILL USE GFS 30M
WINDS...THOUGH WILL MAKE SOME EDITS TO LOWER SPEEDS BY A FEW KT.
WILL THEN USE GFS 10M WINDS 03Z FRI THROUGH 21Z FRI. FROM 00Z
SAT AND BEYOND...WILL TRANSISTION TO ECMWF.

.SEAS...THE 18Z SEA STATE ANALYSIS INDICATED THAT OBSERVED SEAS
CONTINUE TO MATCH UP WELL WITH THE MWW3 FCST VALUES. WILL POPULATE
WAVE GRIDS USING THE MWW3 THROUGH 00Z SAT...THEN WILL TRANSITION
TO ECMWF WAM FOR THE REMAINDER OF FCST.

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


.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
.PZZ800...INNER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE TUE NIGHT.
     GALE POSSIBLE SAT.
.PZZ900...OUTER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE POSSIBLE FRI NIGHT INTO SAT.
.PZZ905...OUTER WATERS FROM CAPE SHOALWATER TO CAPE LOOKOUT...
     GALE POSSIBLE SAT.
.PZZ815...INNER WATERS FROM FLORENCE OR TO POINT ST. GEORGE...
     GALE TUE INTO TUE NIGHT.

.PZ6 CALIFORNIA WATERS...
.PZZ820...INNER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE TUE INTO WED.
     GALE POSSIBLE WED NIGHT INTO THU.
.PZZ920...OUTER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE TUE NIGHT INTO WED.
     GALE POSSIBLE WED NIGHT.
.PZZ825...INNER WATERS FROM POINT ARENA TO PIGEON POINT...
     GALE TUE NIGHT INTO WED.
     GALE POSSIBLE WED NIGHT INTO THU.
.PZZ925...OUTER WATERS FROM POINT ARENA TO PIGEON POINT...
     GALE TUE NIGHT INTO WED.
     GALE POSSIBLE WED NIGHT.
.PZZ830...INNER WATERS FROM PIGEON POINT TO POINT PIEDRAS BLANCAS...
     GALE TUE NIGHT INTO WED.
     GALE POSSIBLE WED NIGHT.
.PZZ930...OUTER WATERS FROM PIGEON POINT TO POINT PIEDRAS BLANCAS...
     GALE TUE NIGHT INTO WED.
     GALE POSSIBLE WED NIGHT.
.PZZ835...INNER WATERS FROM POINT PIEDRAS BLANCAS TO SANTA CRUZ ISLAND, CA...
     GALE POSSIBLE WED NIGHT.
.PZZ935...OUTER WATERS FROM POINT PIEDRAS BLANCAS TO SANTA CRUZ ISLAND, CA...
     GALE POSSIBLE WED NIGHT.

$$

.FORECASTER MUSONDA/KOSIER. OCEAN PREDICTION CENTER.


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