632  
AGPN40 KWNM 290337  
MIMPAC  
 
MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN  
NWS OCEAN PREDICTION CENTER WASHINGTON DC  
837 PM PDT SUN MAY 28 2017  
   
FORECAST DISCUSSION
 
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT  
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.  
 
THE 00Z NCEP SURFACE ANALYSIS SHOWS A LOW PRESSURE TROUGH OVER  
THE WESTERN CONUS AND SOUTHERN BRITISH COLUMBIA WHILE A HIGH  
PRESSURE RIDGE EXTENDS ACROSS THE PZ5 WATERS, NORTHERN PZ6 WATERS  
AND JUST WEST OF THE REMAINDER OF THE PZ6 WATERS. THE TROUGH IS  
EXPECTED TO PERSIST NEAR THE CALIFORNIA COAST THROUGH FRIDAY  
NIGHT. A WEAKENING COLD FRONT WILL MOVE E OVER THE PZ5 WATERS  
LATER WEDNESDAY AND WEDNESDAY NIGHT, FOLLOWED BY ANOTHER WEAK  
COLD FRONT LATE THU AND THU NIGHT, WHILE ASSOCIATED LOW PRESSURE  
REMAINS WELL NW OF THE WATERS. OTHERWISE, THE RIDGE WILL PREVAIL  
OVER THE OFFSHORE WATERS DURING THE FORECAST PERIOD. LATEST  
SURFACE OBSERVATIONS INDICATE MODERATELY STRONG NW WINDS (20 TO  
25 KT WITH SOME HIGHER GUSTS) FROM SOME OF THE COASTAL BUOYS  
ALONG THE CENTRAL CALIFORNIA COAST SOUTH TO NEAR THE CHANNEL  
ISLANDS. FROM AVAILABLE DATA WINDS ARE LIGHT, 5 TO 15 KT,  
ELSEWHERE.  
 
MODELS...THE MEDIUM RANGE MODELS AND 00Z NAM ARE IN VERY GOOD  
OVERALL AGREEMENT ACROSS THE OFFSHORE WATERS THROUGH THU NIGHT.  
THE CONSENSUS OF THE MODELS SHOWS WINDS TO 25 KT IN NW FLOW OVER  
THE COASTAL AND INNER OFFSHORE ZONES OF THE CENTRAL CALIFORNIA  
WATERS FOR TONIGHT AND ESPECIALLY MONDAY INTO WEDNESDAY NIGHT.  
THEN AS THE MODEL CONSENSUS CALLS FOR THE LOW PRESSURE NW OF THE  
WATERS TO LIFT NW AWAY FROM THE AREA LATER THURSDAY INTO FRIDAY  
NIGHT ALLOWING THE EASTERN PACIFIC HIGH TO BUILD NE OVER THE  
WATERS, INCREASING THE GRADIENTS FRIDAY AND FRIDAY NIGHT. THE  
EXCEPTION IS THE OUTLIER 12Z ECMWF WHICH DEVELOPS A LOW NEAR THE  
WASHINGTON WATERS FRIDAY. WILL THEREFORE CONTINUE USE OF THE 12Z  
GFS SUPPORTED BY OTHER GUIDANCE THROUGH THE FORECAST PERIOD WITH  
18Z GFS SHOWING LITTLE CHANGE.  
 
SEAS...THE 12Z ENP WAVEWATCH III AND ECMWF WAM BOTH INITIALIZED  
REASONABLY WELL OVER THE OFFSHORE WATERS VERSUS AVAILABLE  
OBSERVATIONS. THE MODELS ARE IN GOOD OVERALL AGREEMENT THROUGH  
THURSDAY NIGHT, SO WILL CONTINUE USE OF A 50/50 BLEND OF THE  
WAVEWATCH/ECMWF WAM FOR TONIGHT THROUGH THU NIGHT IN ORDER TO  
SMOOTH OUT THE MODEL DIFFERENCES. THEN SINCE ECMWF IS  
DISREGARDED, WILL USE THE 12Z NWW3 FOR FRIDAY AND FRIDAY NIGHT.  
-----------------------------------------------------------------  
PREVIOUS DISCUSSION...  
 
UPDATE...THE 12Z NCEP SURFACE ANALYSIS SHOWS A LOW PRES TROUGH  
OVER WRN CONUS, WITH A HIGH PRES RIDGE OVER THE OFFSHORE WATERS.  
THE TROUGH IS EXPECTED TO PERSIST NEAR THE CALIFORNIA COAST  
THROUGH FRI NIGHT. A WEAK COLD FRONT WILL MOVE E OVER THE  
WASHINGTON AND OREGON OFFSHORE WATERS LATER WED AND WED NIGHT,  
FOLLOWED BY ANOTHER WEAK COLD FRONT LATE THU INTO EARLY FRI.  
OTHERWISE, THE RIDGE WILL PREVAIL OVER THE OFFSHORE WATERS DURING  
THE FORECAST PERIOD. LATEST AVAILABLE ASCATB HI-RES AND ASCATB  
PASSES SHOW LIGHT WINDS IN THE 5 TO 15 KT RANGE ACROSS THE  
OFFSHORE WATERS, EXCEPT FOR WINDS TO 20 KT OVER THE SRN  
CALIFORNIA WATERS.  
 
MODELS...THE 12Z MEDIUM RANGE MODELS ARE IN VERY GOOD OVERALL  
AGREEMENT ACROSS THE OFFSHORE WATERS THROUGH THU NIGHT. THE  
CONSENSUS OF THE MODELS SHOWS WINDS TO 25 KT IN NW FLOW OVER THE  
COASTAL AND INNER OFFSHORE ZONES OF THE CENTRAL CALIFORNIA WATERS  
FOR MON INTO TUE NIGHT. THE 12Z ECMWF LOOKS LIKE AN OUTLYER  
SOLUTION FOR FRI AND FRI NIGHT, BECAUSE IT FORMS A LOW PRES  
CENTER JUST NORTH OF THE PZ5 AREA, WHILE THE OTHER 12Z MODELS  
SHOW A RIDGE THERE. WILL USE THE REPRESENTATIVE 12Z GFS 10M  
SOLUTION FOR THE WIND GRIDS OVER THE ENTIRE FORECAST PERIOD.  
 
SEAS...THE 12Z ENP WAVEWATCH AND 12Z ECMWF WAM BOTH INITIALIZED  
REASONABLY WELL OVER THE OFFSHORE WATERS VERSUS AVAILABLE  
OBSERVATIONS. THE MODELS ARE IN GOOD OVERALL AGREEMENT THROUGH  
THU NIGHT, WITH ONLY MINOR DIFFERENCES NOTED, SO WILL USE A  
50/50 BLEND OF THE 12Z WAVEWATCH/WAM FOR TONIGHT THROUGH THU  
NIGHT IN ORDER TO SMOOTH OUT THE MODEL DIFFERENCES. THEN WILL USE  
THE 12Z ENP WAVEWATCH EXCLUSIVELY FOR FRI THROUGH THE REST OF  
THE FORECAST PERIOD, IN ORDER TO BE CONSISTENT WITH THE PREFERRED  
12Z GFS SOLUTION.  
   
EXTRATROPICAL STORM SURGE GUIDANCE
 
N/A.  
   
WARNINGS
 
PRELIMINARY.  
   
PZ5 WASHINGTON/OREGON WATERS
 
 
NONE.  
   
PZ6 CALIFORNIA WATERS
 
 
NONE.  
 

 
 
.FORECASTER BANCROFT/SCOVIL. OCEAN PREDICTION CENTER.  
 
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