203  
FXHW01 KWNH 230802  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
301 AM EST SAT JAN 23 2021  
 
VALID 00Z SUN JAN 24 2021 - 00Z SUN JAN 31 2021  
 
LATEST MODELS AND ENSEMBLES CONTINUE TO DEPICT A SIMILAR PATTERN  
EVOLUTION THROUGH THE PERIOD. STRONG HIGH PRESSURE TO THE  
NORTH/NORTHEAST OF THE STATE, PERIODICALLY REINFORCED BY UPSTREAM  
HIGH CENTERS, WILL MAINTAIN BRISK TO STRONG EASTERLY/SOUTHEASTERLY  
WINDS FOR MOST OF THE PERIOD. RAINFALL WILL FOCUS OVER WINDWARD  
AND MOUNTAIN LOCALES BUT SOME ACTIVITY COULD STRAY TO OTHER AREAS  
AS WELL. FROM THE WEEKEND INTO THE FIRST HALF OF NEXT WEEK  
GUIDANCE CONTINUES TO SHOW THE NORTHWESTWARD TRANSPORT OF ENHANCED  
MOISTURE TOWARD/ACROSS THE ISLANDS IN RESPONSE TO FLOW BETWEEN A  
DEVELOPING UPPER/SURFACE SYSTEM JUST WEST OF 170W LONGITUDE AND  
THE DEEP-LAYER RIDGE TO THE NORTH/NORTHEAST OF THE STATE.  
REPOSITIONING OF THE UPPER RIDGE SHOULD HELP TO PUSH DRIER AIR  
INTO THE REGION FROM MIDWEEK ONWARD.  
 
ALTHOUGH GUIDANCE AGREES ON THE GENERAL SCENARIO, THERE ARE STILL  
SIGNIFICANT DIFFERENCES IN THE MAGNITUDE OF RAINFALL TOTALS  
ASSOCIATED WITH NEXT WEEK'S MOISTURE SURGE. THESE DIFFERENCES ARE  
MOST PRONOUNCED OVER THE NORTHWESTERN ISLANDS WHILE THERE IS  
BETTER AGREEMENT IN PRINCIPLE FOR SOME LOCALLY HEAVY RAINFALL OVER  
THE BIG ISLAND. GFS RUNS (WITH SUPPORT IN PRINCIPLE FROM THE GEFS  
MEAN THOUGH OF COURSE WITH LIGHTER VALUES) CONTINUE TO BE HEAVIEST  
OVER THE NORTHWESTERN ISLANDS WITH LATEST ECMWF/UKMET/CMC RUNS ALL  
SUGGESTING THAT THE AXIS OF HEAVIEST RAINFALL SHOULD LIE FARTHER  
WEST. THIS DIFFERENCE CORRESPONDS TO THE GFS/GEFS BEING WEAKEST  
WITH THE UPPER RIDGE TO THE NORTH OF THE STATE AND ALLOWING FOR  
LOWER SURFACE PRESSURES OVER/SOUTHWEST OF THE ISLANDS. THE  
GUIDANCE COMPARISON FOR MASS FIELDS WOULD SUPPORT HEDGING SOMEWHAT  
AWAY FROM THE GFS/GEFS SCENARIO. ON THE OTHER HAND GUIDANCE AS A  
WHOLE HAS TRENDED HIGHER WITH PRECIPITABLE WATER VALUES OVER THE  
PAST 24 HOURS. THE 00Z ECMWF IS ONCE AGAIN BETWEEN THE HIGHEST  
00Z GFS AND SOMEWHAT LOWER 00Z GEFS/12Z ECMWF MEANS. THE HIGHER  
TREND FOR MOISTURE OFFERS POTENTIAL FOR AT LEAST LOCALLY HEAVIER  
AMOUNTS THAN WHAT THE NON-GFS CLUSTER IS ADVERTISING.  
 
RAUSCH  
 

 
 
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