353  
FXHW01 KWNH 290747  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
347 AM EDT SUN SEP 29 2024  
 
VALID 00Z MON SEP 30 2024 - 00Z MON OCT 07 2024  
 
TODAY'S GUIDANCE CONTINUES TO SHOW MODERATE TRADES THROUGH MOST OF  
THIS COMING WEEK WITH WINDWARD/MOUNTAIN FOCUS FOR SHOWERS THAT  
SHOULD BE FAIRLY LIGHT MOST OF THE TIME AS PRECIPITABLE WATER  
VALUES HOVER AROUND OR SLIGHTLY BELOW NORMAL. UPPER RIDGING IN  
PLACE THROUGH WEDNESDAY SHOULD ALSO HELP TO TEMPER RAINFALL  
AMOUNTS. MODELS/ENSEMBLES AGREE THAT THE UPPER RIDGE WILL  
COLLAPSE AFTER MIDWEEK, WITH SOME TYPE OF CYCLONIC FLOW ALOFT  
LIKELY BECOMING MORE PREVALENT OVER AND NORTH/WEST OF THE MAIN  
ISLANDS LATE WEEK INTO THE WEEKEND. HOWEVER THERE IS NO REAL  
CLUSTERING AMONG THE DYNAMICAL/MACHINE LEARNING GUIDANCE FOR THE  
DETAILS INCLUDING WHERE A COMPACT UPPER LOW MAY EVOLVE (FOR  
EXAMPLE, JUST NORTHEAST OF THE MAIN ISLANDS IN THE 00Z GFS BUT  
WELL WEST IN THE 00Z ECMWF). FOR THE PURPOSES OF A DETERMINISTIC  
FORECAST, THE BROADER TROUGH SEEN IN THE ENSEMBLE MEANS IS A  
REASONABLE OPTION WHILE AWAITING BETTER AGREEMENT. THIS UPPER  
TROUGH MAY HELP TO WEAKEN THE TRADES SOMEWHAT AROUND LATE WEEK  
INTO THE WEEKEND, WHILE POSSIBLY INCREASING RAINFALL A BIT (THOUGH  
WITH GUIDANCE GENERALLY NOT TOO ENTHUSIASTIC).  
 
RAUSCH  
 

 
 
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