775  
AGPN40 KWNM 290852  
MIMPAC  
 
MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN  
NWS OCEAN PREDICTION CENTER WASHINGTON DC  
152 AM PDT FRI MAY 29 2020  
   
FORECAST DISCUSSION
 
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT  
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.  
 
PER THE MOST RECENT NCEP 06Z PRELIMINARY SURFACE ANALYSIS THE  
WEAKENING COLD FRONT HAS PROGRESSED INLAND AND ENTERED THE  
PZZ920 WATERS. HIGH PRESSURE REMAINS WELL W OF THE AREA. AN  
OCCLUDED FRONT STRETCHES FROM THE W INTO THE PZZ940 WATERS WITH  
THE ASSOCIATED PARENT LOW SW OF THE SOUTHERN PZ6 WATERS. A  
THERMAL TROUGH STRETCHES FROM CENTRAL CALIFORNIA INTO SOUTHERN  
OREGON. RECENT ASCT DATA FROM 0445Z SHOW A BAND OF WINDS TO 25 KT  
STRETCHING FROM THE NORTHERN PZ5 WATERS TO THE NORTHERN PZ6  
WATERS. THE GREATEST WINDS ARE LOCATED ALONG THE COLD FRONT.  
 
THE COLD FRONT WILL CONTINUE TO WEAKEN AND MOVE SE ACROSS THE  
OFFSHORE WATERS THROUGH TONIGHT. THE THERMAL TROUGH ALONG  
CENTRAL CALIFORNIA WILL EXTEND FURTHER N INTO WASHINGTON BEFORE  
BEING ABSORBED BY AN INLAND LOW SAT. THE OCCLUDED LOW TO THE SW  
OF THE SOUTHERN PZ6 WATERS WILL MOVE NE THROUGH THE SOUTHERN AND  
CENTRAL PZ6 WATERS BEFORE COMING ASHORE SAT NIGHT NEAR POINT  
ARENA. HIGH PRESSURE WELL W OF THE WATERS WILL CONTINUE TO MOVE  
E/NE BEFORE STALLING SUN JUST W OF THE BORDER OF THE PZ5 AND PZ6  
OUTER WATERS. THE HIGH CENTER WILL THEN RECEDE SW AS A COLD  
FRONT APPROACHES THE NORTHERN PZ5 WATERS. A HIGH PRESSURE RIDGE  
AXIS WILL STRETCH NE AHEAD OF THE COLD FRONT THROUGH THE PZ5  
WATERS. TUE THE COLD FRONT WILL MOVE INTO THE NORTHWESTERN PZ5  
WATERS AND FORCE THE RIDGE AXIS SE. THE COLD FRONT WILL QUICKLY  
WEAKEN AS IT ENTERS THE OFFSHORE WATERS AND THE HIGH PRESSURE  
WILL FILL BACK INTO THE PZ5 WATERS TUE NIGHT. WITH HIGH PRESSURE  
FILLING BACK INTO THE OFFSHORE WATERS THE PRESSURE GRADIENT WILL  
TIGHTEN DUE TO THE REFORMATION OF THE CALIFORNIA THERMAL TROUGH.  
AN AREA OF ENHANCED WINDS TUE NIGHT IN THE INNER CENTRAL PZ6  
WATERS ARE EXPECTED.  
 
GLOBAL MODELS CONTINUE TO BE IN GOOD AGREEMENT FOR MOST OF THE  
FORECAST PERIOD. THE MAIN DIFFERENCE AMONG THE MODELS CONTINUE TO  
BE THE TIMING OF THE COLD FRONT PASSING THROUGH THE PZ5 WATERS AT  
THE END OF THE FORECAST PERIOD. ANOTHER POINT OF CONTENTION AMONG  
THE MODELS IS THE FORMATION OF A HIGH CENTER FOLLOWING THE COLD  
FRONT PASSAGE. THIS NEW HIGH APPEARS N OF THE PZ5 WATERS IN BOTH  
THE GFS AND ECMWF, BUT IS NOT QUITE AS EVIDENT IN THE UKMET. THE  
CMC DOES NOT APPEAR TO HAVE THE HIGH AT THIS TIME. HIGH  
PLACEMENT IN THE GFS AND ECMWF VARIES BASED ON HOW QUICKLY THE  
COLD FRONT MOVES INLAND. THE ECMWF BEING A BIT QUICKER WITH THE  
FRONT HAS THE HIGH A BIT FURTHER E THAN THE GFS. THE UKMET HAS  
THE HIGH WELL SW OF BOTH THE GFS AND ECMWF POSITION. GIVEN THE  
CLOSE AGREEMENT BETWEEN THE GFS AND ECMWF, I WILL BLEND THE TWO  
FOR MY SFC WIND GRIDS THROUGH MON 21Z. BEYOND THAT TIME I WILL  
POPULATE WITH THE ECMWF FOR THE REMAINDER OF THE FORECAST PERIOD.  
WITH MODELS SPREADING A BIT MORE AT THE END OF THE FORECAST  
PERIOD WHEN COMPARED TO THE LAST FEW RUNS MY CONFIDENCE IS  
DOWNGRADED TO MODERATE.  
   
SEAS
 
SEAS INITIALIZED WELL WITH BOTH THE NWW3 AND ECMWF WAM.  
IN ORDER TO MAINTAIN CONTINUITY WITH THE SFC WINDS I WILL  
POPULATE WAVE GRIDS WITH THE SAME PHILOSOPHY. FOR THE BEGINNING  
OF THE FORECAST THROUGH MON 21Z I WILL USE A NWW3/ECMWF WAM 1:1  
BLEND. FOR THE REMAINDER OF THE FORECAST PERIOD I WILL POPULATE  
WITH ECMWF WAM.  
 
   
EXTRATROPICAL STORM SURGE GUIDANCE
 
 
   
WARNINGS
 
PRELIMINARY.  
   
PZ5 WASHINGTON/OREGON WATERS
 
 
NONE.  
   
PZ6 CALIFORNIA WATERS
 
 
NONE.  
 

 
 
.FORECASTER JOSEPH. OCEAN PREDICTION CENTER.  
 
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