343  
FXHW01 KWNH 161230  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
829 AM EDT MON OCT 16 2017  
 
VALID 00Z TUE OCT 17 2017 - 00Z TUE OCT 24 2017  
 
MODELS AND ENSEMBLES SHOW GENERALLY GOOD AGREEMENT ON THE LARGE  
SCALE PATTERN ACROSS THE CENTRAL PACIFIC THROUGH THE NEXT WEEK.  
UPPER RIDGE INITIALLY NORTHWEST OF HAWAII WILL MOVE A BIT EAST  
OVER THE ISLANDS AS IT GRADUALLY WEAKENS. MEANWHILE, AN UPPER LOW  
WELL NORTHEAST OF THE STATE WILL ALSO SLOWLY WEAKEN OVER THE NEXT  
WEEK, HAVING VERY LITTLE IN THE WAY OF SENSIBLE WEATHER IMPACTS  
OVER HAWAII. LOW-LEVEL EAST-NORTHEASTERLY FLOW OF 15-25 KT WILL  
PERSIST ACROSS THE ISLANDS THROUGH MOST OF THE NEXT WEEK, AS A  
SURFACE HIGH REMAINS ANCHORED NORTH OF THE STATE. THE PATTERN  
ACROSS THE CENTRAL PACIFIC SHOULD BEGIN TO CHANGE BY LATE NEXT  
WEEKEND AS MOST MODELS AND ENSEMBLES SHOW A SHORTWAVE AMPLIFYING  
ACROSS THE NORTH CENTRAL PACIFIC, WHICH COULD PUSH A COLD FRONT  
SOUTHWARD IN THE GENERAL DIRECTION OF HAWAII. THERE IS A FAIRLY  
LARGE DEGREE OF SPREAD, HOWEVER, AS TO THE EXACT EVOLUTION OF THE  
TROUGH, AND WHETHER A MORE FULL LATITUDE TROUGH AMPLIFIES NORTH OF  
HAWAII (AS SHOWN BY THE GFS AS WELL AS THE GEFS/NAEFS/CMC  
ENSEMBLES) OR WHETHER A SOMEWHAT WEAKER WAVE MOVES EAST MORE  
QUICKLY (AS SHOWN BY THE CMC). THE 00Z ECMWF WAS GENERALLY IN THE  
MIDDLE OF THESE TWO EXTREMES. NONETHELESS, THERE SHOULD BE SOME  
TYPE OF WAVE AMPLIFYING NORTH OF HAWAII BY LATE IN THE WEEKEND,  
WHICH COULD PUSH A FRONT TOWARD THE ISLANDS, BUT IT REMAINS  
UNCLEAR ON HOW QUICKLY THE FRONT WILL MOVE SOUTH TOWARD THE  
ISLANDS.  
 
RYAN  
 

 
 
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