918  
AGPN40 KWNM 170312  
MIMPAC  
 
MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN  
NWS OCEAN PREDICTION CENTER WASHINGTON DC  
812 PM PDT FRI APR 16 2021  
   
FORECAST DISCUSSION
 
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT  
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.  
 
AT THIS TIME I DO NOT PLAN ON MAKING ANY CHANGES TO THE GRIDS OR  
ASSOCIATED GRIDS FORECASTS.  
 
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PREVIOUS DISCUSSION...  
 
.AT 19Z, LATEST AVAILABLE SATELLITE IMAGERY, MARINE AND LAND  
SURFACE OBSERVATIONS AND ANALYSIS DETECT THE AXIS OF 1020-1025  
MB N-S ORIENTED RIDGING FROM JUST W OF BC SOUTH ALONG THE W EDGE  
OF ALL OF THE PACIFIC REGIONAL WATERS EXCEPT JUST W OF THE  
SOUTHERNMOST OUTER WATERS OF PZ6. WEAKER SYSTEMS CONTINUE TO  
IMPACT THE WATERS WELL TO THE W OF THIS RIDGING, MAINLY W OF  
140W AND TRHE CURRENT FORECASTS FOR ANY OF THESE LOWS WILL KEEP  
THEM WELL AWAY FROM THE REGIONAL WATERS FOR THE NEXT 5 DAYS.  
LATEST AVAILABLE BUOY OBSERVATIONS ARE MISSING AS OF THE 18Z  
HOUR. HOWEVER, AN APPROX 1630Z LATE MORNING ASCAT PASS WITH A  
SWATH ACROSS ALL OF THE INNER PZ6 WATERS INDICATED WINDS NO  
HIGHER THAN 15 KT WERE PRESENT ACROSS ALL OF THE INNER WATERS  
AND PORTIONS OF THE OUTER WATERS.  
 
IN THE SHORT TERM FORECAST ARENA, TODAY THRU TUESDAY NIGHT, THE  
AFOREMENTIONED N-S WEAKER NEAR 1020 MB RIDGING WILL REMAIN OVER  
THE SAME GENERAL AREA THRU SAT NIGHT BUT THEN BY 18Z ON SUNDAY  
ANOTHER ANTICYCLONE WITH A 1025-1030 MB CENTER IS PROGGED BY  
MODEL CONSENSUS TO BUILD OUT NEAR 33N130W, W OF THE S P6 OUTER  
WATERS. THE NEAR 1025 MB CENTER WILL MOVE NW TO NEAR 36N140W BY  
12Z MON, THEN MOVE SLOWLY NORTHWARDS AND INTENSIFY TO A NEAR 1035  
MB HIGH SITUATED AOA 40N137W BY 12Z TUE.  
 
AS A RESULT, EXPECT THE VERY WEAK CA COASTAL TROUGH TO REDEVELOP  
LATE SUN NIGHT THEN EXPAND N AND S UP AND DOWN THE COASTS BY  
LATE MON AFTERNOON (UP TO S OR AND DOWN TO S CA). WINDS CONTINUE  
TO INCREASE ACROSS ALL OF THE WATERS MON NIGHT AND TUE, EXCEPT  
FOR ACROSS THE S PZ6 WATERS, WITH THE LATEST (12Z) RUNS OF THE  
GFS AND ECMWF NCEP AS WELL AS THE UKMET AND CMC NON-NCEP MODELS  
INDICATING STRONG SUBGALE NW WINDS ACROSS PORTIONS OF BOTH THE N  
PZ6 INNER AND OUTER WATERS. THEN ON TUE NIGHT THE GFS INDICATES  
POSSIBLE SMALL AREA OF LOW END GALES MAY INFILTRATE THE NORTHERN  
INNER PZ6 WATERS. THIS IS STILL MARGINAL WITH NO LOW END GALES  
INDICATED IN THE ECMWF AS WELL AS THE CMC AND UKMET RUNS. HENCE  
WILL CONTINUE TO USE THE GFS UNTIL 18Z TUE.  
   
EXTENDED
 
WED THRU FRI, ONCE AGAIN THE STRONG RIDGE SITUATED  
BETWEEN 40-45N ALONG 135-137W WILL GRADUALLY ELONGATE (SLIGHTLY  
ARC) INTO MORE OF A N-S ORIENTED SLIGHTLY YET WEAKER 1025 MB  
RIDGE ON WED GRADUALLY DAMPENING TO A 1020 MB RIDGE BY THU, THEN  
BEGINS TO MOVE EAST AND WEAKEN BY DAY 7. ALL OF THE MODELS DO  
SHOW A COLD FRONT MOVING TOWARDS THE PZ5 AND THE NORTHERN PART  
OF PZ6 BY LATE IN THE DAY FWIW. WILL USE THE 12Z ECMWF FOR THE  
WINDS FROM 18Z TUE TILL THE END OF THE FP.  
   
SEAS
 
18Z WAVEHEIGHT ANALYSIS WAS WITHOUT BUOY OBSERVATIONS  
BUT THE INHERITED GRIDDED COMBINED SEAS WAS WITHIN 1 FOOT ACROSS  
ALL OF THE REGIONAL WATERS. FOR THE FORECAST WILL CONTINUE TO  
USE THE LATEST GFSWAVE FOR TONIGHT THRU 18Z TUE. THEREAFTER WILL  
UTILIZE THE ECMWF WAVE FROM 18Z TUE TILL THE END OF THE FP.  
   
EXTRATROPICAL STORM SURGE GUIDANCE
 
 
   
WARNINGS
 
PRELIMINARY.  
   
PZ5 WASHINGTON/OREGON WATERS
 
 
NONE.  
   
PZ6 CALIFORNIA WATERS
 
 
NONE.  
 

 
 
.FORECASTER SHAW/FUTTERMAN. OCEAN PREDICTION CENTER.  
 
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