Marine Interpretation Message
Issued by NWS

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AGPN40 KWNM 300325
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
825 PM PDT SUN MAY 29 2016

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

THE SAT IMG HAS A NARROW AREA WITH FEW CLDS OVER THE ERN PARTS OF
THE NRN WATERS WHILE THE REST OF THE REGION IS QUITE CLOUDY WITH
VERY ISOL AND SPORADIC LIGHTNING STRIKES. THE RADAR DOES NOT HAVE
ANY INDICATION OF TSTMS CELLS ACROSS THE FORECAST REGION. THE SREF
MODEL HAS LESS THAN 5 PERCENT CHANCE OF SEV TSTMS ACROSS THE
FORECAST WATERS AND NO INDICATION OF ANY CHANCES TO INCREASE THE
PROBS IN THE SHORT TERM. AT 00Z INLAND LOW PRES 1010 MB OVER NRN
CA HAS A TROF THAT EXTENDS SE INTO ANOTHER INLAND LOW PRES 1006 MB
OVER AZ. A BROAD AREA OF HIGH PRES TO THE W OF THE REGION WITH ONE
CENTER 1028 MB NEAR 38N133W AND ANOTHER 1028 MB NEAR
44N132W...EXTENDS INTO MOST OF THE REGION. THE ERN PARTS OF THE
CENTRAL REGION THAT ARE CLOSER TO THE NRN CA LOW HAVE A RELATIVELY
TIGHTER PRES GRADIENT AND THAT IS THE AREA WHERE THE WINDS ARE
MAXIMUM AT 30 KT. OTHERWISE THE REGION HAS A RELAXED PRES GRADIENT
AND WINDS WITH MOSTLY A NORTH COMPONENT RANGE BETWEEN 10 AND 25
KT. THE LAST ASCAT PASS WAS AT 1818Z AS DESCRIBED BELOW IN THE
PREVIOUS DISCUSSION SECTION. THE SEAS ARE EQUALLY SMALL WITH PEAKS
TO 11 FT OVER THE SRN WATERS. SEAS RANGE BETWEEN 3 AND 6 FT OVER
THE NRN WATERS. THE NWW3 MULTI GRID WAVE MODEL FITS WITH THE SEAS
PATTERN BUT IS UNDRDONE BY 2 FT ON THE PEAK VALUE OVER THE SRN
WATERS. OTHERWISE...NWW3 IS VERY CLOSE TO THE ECMWFWAVE MODEL TOO
AND BOTH MODELS AGREE WELL ON KEEPING THE SEAS ABOUT THE SAME IN
THE SHORT TERM AND SUBSIDING OVER THE SRN WATERS AS THEY BUILD
SLIGHTLY OVER THE NRN WATERS IN THE EXTENDED PERIOD. SEAS WILL
PEAK AT 12 FT AGAIN WED OVER THE SRN WATERS THEN SUBSIDE THRU THE
REST OF THE FORECAST PERIOD.

AN UPPERLEVEL RIDGE JUST W OF THE REGION HAS MAINTAINED REDUCED
ENERGY OVER THE REGION AND HAS ALSO BLOCKED MOST OF THE ANERGY
EMBEDED IN AN UPPER LEVEL TROF TO THE W OF IT FROM ADVANCING EAST
TOWARD THE WATERS. THIS RIDGE WILL SLOWY MOVE E ACROSS THE REGION
AND THAT WILL PREVENT ANY ENERGY TO REACH THE WATERS DURING THE
FORECAST PERIOD. THE RIDGE DOMINANCE WILL MAINTAIN A RELAXED PRES
GRADIENT OVER THE REGION AND WINDS WILL THEREFORE REMAIN BELOW
GALE FORCE THRESHOLD.

THE GLOBAL MODELS HAVE INITIALIZED WELL AND HAVE BEEN QUITE
CONSISTENT. WITH JUST MINOR DIFFERENCES ON THE ORIENTAION OF THE
RIDGE AXIS. OTHERWISE EVEN WITH THOSE MINOR DIFFERENCES THE MAIN
SYNOPTIC PATTERN REMAINS THE SAME. ALL THE GLOBAL MODELS SUGGEST
INITIALLY ONE CENTER BUT A BROAD AREA OF HIGH PRES WHILE THE SAT
IMG SUGGESTED TWO CENTERS. IN ADDITION THE MODELS ARE WITHIN 2 MB
MARGIN ERROR WITH THE OBSERVED CENTRAL HIGH PRES VALUE. THE
UKMETHR AND GFS HAVE A MUCH CLOSER SOLUTION THAN THE REST AND
BOTH MODELS HAVE MATCHED A TARDY BETTER ON THE AXIS ORIENTAION
THAN THE REST AND SO WILL CONTINUE WITH THE GFS MODEL SOLUTION
LIKE THE DAY SHIFT. IN THE SHORT TERM AT THE SFC...HIGH PRES WILL
SLOWLY SHIFT NE AND THE HIGH PRES CENTER WILL MOVE INTO THE NRN
WATERS AS THE RIDGE DOMINATES THE REGION. THE INLAND TROF WILL
WEAKEN FARTHER AND THE PRES GRADIENT WILL FARTHER RELAX OVER THE
ERN PARTS. A RELAXED PRES GRADIENT WILL PERSIST OVER THE REGION
INTO THE EXTENDED PERIOD.

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

THE 18Z OPC SFC ANALYSIS SHOWS AN ENHANCED PRES GRADIENT OVER THE
NRN/CENTRAL CA WATERS BETWEEN A 1026 MB HIGH W OF THE FCST AREA
AND A 1012 MB LOW OVER NRN CA. UNFORTUNATELY THE ASCAT PASSES THIS
AFTN MISSED THE AREA OF STRONGEST WINDS OFF THE CA COAST. OTHERWISE
NO OTHER SFC FEATURES TO DISCUSS OVER THE OPC WATERS AS THE HIGH
PRES RIDGE W OF THE WATERS DOMINATES THE PATTERN.

THE GLOBAL MODELS REMAIN IN VERY GOOD AGREEMENT THROUGH MOST OF
THE FCST PERIOD. SFC HIGH PRES WILL MOVE NE INTO THE PZ5 WATERS BY
EARLY MON...SHIFTING THE PINCHED GRADIENT AND 20-30 KT WINDS NWD
INTO THE SRN OR WATERS AS WELL. THE RIDGE WILL WEAKEN ON WED BUT
REMAIN ACROSS THE SRN PZ5/NRN PZ6 WATERS THROUGH LATE WEEK AS THE
GRADIENT RELAXES AND WIND SPEEDS GRADUALLY DIMINISH. THE NEXT LOW
PRES SYSTEM APPROACHES THE PZ5 WATERS LATE THU/EARLY FRI...BUT THE
GFS/ECMWF BOTH KEEP THE RIDGE AXIS ENTRENCHED ACROSS THE SRN
PZ5/NRN PZ6 WATERS. THIS SHOULD STEER THE LOW AND THE STRONGEST
WINDS NW OF THE PZ5 WATERS...WITH HIGHEST WIND SPEEDS OF 20-25 KT
EXPECTED ACROSS THE EXTREME NW WA WATERS ON FRI MORNING.

THE 12Z GFS WAS THE MODEL OF CHOICE TODAY...ALTHOUGH THE ECMWF WAS
VERY SIMILAR FOR MUCH OF THE PERIOD. USED A BLEND OF THE 30/10M
GFS WINDS THROUGH TUE NIGHT TO BETTER CAPTURE THE ENHANCED NLY
FLOW DISCUSSED PREVIOUSLY...FOLLOWED BY THE 10M GFS WINDS THROUGH
FRI AFTER COLLABORATING WITH A COUPLE OF THE COASTAL WFOS. THE
ECMWF TRACKS THE LOW A BIT CLOSER TO THE OUTER PZ5 WATERS LATE
THU/EARLY FRI. BUT THE ECMWF IS ALSO WEAKER WITH IT...SO THE NET
RESULT IS A VERY SIMILAR WIND FIELD TO THE PREFERRED GFS SOLUTION.

.SEAS...SIMILAR TO YESTERDAY...USED A BLEND OF THE NWW3/ECMWF WAM
THROUGH TUE MORNING TO BUMP UP SEAS A BIT BASED ON THE LATEST SEA
STATE ANALYSES. AFTERWARDS...FAVORED THE NWW3 TO MATCH UP WITH
THE FCST WINDS THROUGH THE REST OF THE PERIOD.


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



.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
     NONE.

.PZ6 CALIFORNIA WATERS...
     NONE.

$$

.FORECASTER MUSONDA/REINHART. OCEAN PREDICTION CENTER.



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