Marine Interpretation Message
Issued by NWS

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AGPN40 KWNM 210231
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
731 PM PDT SAT SEP 20 2014

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

ATTM I DONT PLAN ON MAKING MANY ADJUSTMENTS TO THE CURRENT GRIDS
AND ASSOCIATED FCST...THE BEST CHANCE FOR GALES REMAIN ON WED AS
STRONG LOW CENTER APPROACHES PZ5 WATERS. LARGE SWELL WILL ALSO
MOVE INTO WATERS. CURRENT OBS ARE IN GOOD AGREEMENT WITH PRIOR CST
AND NO REASON TO MAKE CHANGE IN SHORT TERM IS NEEDED.

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

THE 18Z SFC ANALYSIS INDICATED WEAK HIGH PRES RIDGE EXTENDING FROM
SW CANADA ACROSS WA/OR OFFSHORE WATERS AND SW. WEAK LOW WAS OVER
THE OR COASTAL WATERS WITH TROG EXTENDING N. ANOTHER LOW WAS
LOCATED NEAR 43N142W WITH STATIONARY FRONT EXTENDING NE.

THE 12Z MODELS ARE IN REASONABLE AGREEMENT THROUGH MOST OF THE
FCST PERIOD...HOWEVER SIGNIFICANT DIFFERENCES APPEAR BY DAY 5 AND
CONTINUE BEYOND. DURING THE SHORT TERM PERIOD FROM TONIGHT THROUGH
MON NIGHT THERE ARE NO MAJOR ISSUES. THE HIGH PRES RIDGE WILL
WEAKEN AS THE LOW TO THE W OF AREA MOVES NE WITH COLD FRONT MOVING
SLOWLY E. THE FRONT WILL THEN MOVE INTO THE WA/OR/N CA WATERS
LATER SUN AFTERNOON INTO EARLY MON WHILE WEAKENING. THEN ATTENTION
TURNS TO STRONG LOW WHICH IS FCST TO APPROACH THE WA/OR WATERS
LATER TUE AND WED...THEN TURN N. THE MAIN FCST CHALLENGE AS USUAL
IS THE TIMING OF ONSET OF GALES OVER THE OFFSHORE WATERS. THE 12Z
GFS IS A BIT FASTER THAN THE PAST FEW RUNS WITH EVEN THE 10M WINDS
INDICATING GALES OVER THE FAR WRN WA WATERS AS EARLY AS 12Z WED.
THE UKMET IS VERY SIMILAR TO THIS TIMING AND ALSO HAS GALES OVER
THE WRN PORTIONS OF WA/OR WATERS BY 12Z WED. THE ECMWF AND CMC
DELAY THE GALES UNTIL AFTER 12Z WED. TO TRY TO MAINTAIN CONTINUITY
WILL DEFER TO ECMWF HERE AS IT HAS BEEN MORE CONSISTENT. LOOKING
FURTHER AHEAD TO THU...MODEL DIFFERENCES INCREASE WITH ECMWF
INDICATING LOW BECOMING STATIONARY NEAR THE NW CORNER OF WA
WATERS...WHILE GFS AND CMC MOVE LOW N AND DEVELOP AOTHER LOW JUST
N OF THE WA WATERS. UKMET A MAJOR OUTLIER IN DEVELOPING STRONG LOW
WELL W OF N CA WATERS THEN MOVING RAPIDLY E TO W OF N CA WATERS BY
12Z FRI WHILE INTENSIFYING. WILL GO CLOSER TO GFS/CMC HERE AND
THIS IS ALSO FAVORED BY WPC MEDIUM RANGE. IN SUMMARY...WILL
POPULATE GRIDS USING THE 12Z GFS 10M WINDS THROUGH 09Z TUE...THEN
12Z ECMWF 12Z TUE THROUGH 12Z THU...THEN GFS 30M WINDS FOR
REMAINDER.

.SEAS...ALTIMETER PASS FROM 1356Z INDICATED MAXES OF AROUND 10 FT
OVER THE WA AND OREGON OFFSHORE WATERS WHICH WAS WITHIN A FT OF
THE MWW3 GUIDANCE. AS OF 20Z...AVBL SHIP AND BUOY OBS WERE MOSTLY
WITHIN A FT OF THE MDL VALUES...EXCEPT OVER THE WA COASTAL WATERS
WHERE OBSERVED VALUES WERE STILL 2 TO 3 FT ABOVE THE MDL. FOR THE
GRIDS...PLAN ON USING THE MWW3 VALUES THROUGH 09Z TUE...THEN WILL
USE THE ECMWF WAM FROM 12Z TUE THROUGH 12Z THU SINCE WILL BE USING
THE ECMWF WIND GRIDS. THEN WILL TRANSITION BACK TO MWW3 FOR
REMAINDER OF PERIOD.

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



.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
.PZZ800...INNER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE POSSIBLE WED.
.PZZ900...OUTER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE POSSIBLE WED.
.PZZ805...INNER WATERS FROM CAPE SHOALWATER TO CAPE LOOKOUT...
     GALE POSSIBLE WED.
.PZZ905...OUTER WATERS FROM CAPE SHOALWATER TO CAPE LOOKOUT...
     GALE POSSIBLE WED.
.PZZ810...INNER WATERS FROM CAPE LOOKOUT TO FLORENCE OR...
     GALE POSSIBLE WED.
.PZZ910...OUTER WATERS FROM CAPE LOOKOUT TO FLORENCE OR...
     GALE POSSIBLE WED.
.PZZ915...OUTER WATERS FROM FLORENCE OR TO POINT ST. GEORGE...
     GALE POSSIBLE WED.

.PZ6 CALIFORNIA WATERS...
     NONE.

$$

.FORECASTER SHAW/KOSIER. OCEAN PREDICTION CENTER.


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