537  
FXHW01 KWNH 041210  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
809 AM EDT SAT NOV 04 2017  
 
VALID 00Z SUN NOV 05 2017 - 00Z SUN NOV 12 2017  
 
REX BLOCK PATTERN WITH AN AXIS WELL WEST OF HAWAII NORTH TO ALASKA  
IS FORECAST TO PROPAGATE SLOWLY WESTWARD THROUGH THE NEXT WEEK,  
KEEPING THE FLOW PATTERN ACROSS HAWAI'I RELATIVELY STABLE. UPPER  
RIDGING CENTERED OVERHEAD IS FORECAST BY ALL GUIDANCE TO SLOWLY  
WEAKEN INTO NEXT WEEK, ALTHOUGH, WEAKLY POSITIVE HEIGHT ANOMALIES  
ARE FORECAST BY THE ECMWF ENSEMBLE TO REMAIN IN PLACE ACROSS THE  
ISLANDS. AT THE SURFACE A WEAKENING HIGH INITIALLY CENTERED WELL  
NORTHEAST OF HAWAI'I WILL RESULT IN SLIGHTLY WEAKENING EASTERLIES,  
FROM 20 KT TODAY TO 10-15 KT BY THE MIDDLE OF NEXT WEEK. THIS FLOW  
PATTERN WILL KEEP RELATIVELY LOW PRECIPITABLE WATER VALUES IN  
PLACE, ESPECIALLY FROM SUNDAY ONWARD WHEN GUIDANCE SHOWS VERY DRY  
AIR ORIGINATING IN THE NORTHEASTERN PACIFIC ADVECTING ACROSS  
HAWAI'I. THEREFORE, EXPECT SHOWERS TO BE GENERALLY FOCUSED ALONG  
WINDWARD TERRAIN, BECOMING EVEN MORE SPARSE THROUGH THE NEXT WEEK.  
A TROUGH FORECAST TO AMPLIFY ACROSS THE NORTHEASTERN PACIFIC BY  
EARLY-MID NEXT WEEK WILL FORCE THE TAIL END OF A COLD FRONT  
SOUTHWARD TOWARD THE ISLANDS, ALTHOUGH THE MODEL CONSENSUS IS THAT  
THE FRONT SHOULD REMAIN WELL NORTH OF THE ISLANDS THROUGH NEXT  
SATURDAY AS IT WASHES OUT.  
 
RYAN  
 

 
 
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