659  
FXHW01 KWNH 181229  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
729 AM EST THU JAN 18 2018  
 
VALID 00Z FRI JAN 19 2018 - 00Z FRI JAN 26 2018  
 
MODELS AND ENSEMBLES AGREE THAT A STRONG SURFACE HIGH WILL BRIDGE  
TO THE NORTH OF THE STATE OVER THE NEXT FEW DAYS AND PRESSURE  
GRADIENTS UNDERNEATH SUPPORT BRISK ISLAND TRADES. A LINGERING  
SHEARLINE FURTHER WEAKENS OVER THE STATE AND THE PATTERN REMAINS  
DRY DURING THIS PERIOD UNDER A STABLE UPPER RIDGE.  
 
WEAK SHORTWAVE TROUGH AND HEIGHT FALL APPROACH FROM THE WEST  
WEAKENS THIS RIDGE OVER THE WEEKEND INTO EARLY NEXT WEEK AS TRADE  
FLOW DECREASE TO MODERATE LEVELS IN RESPONSE TO THE SHIFT OF THE  
SUPPORTING SURFACE HIGH INTO THE EASTERN PACIFIC. THIS ALLOWS A  
GRADUAL RETURN OF MOISTURE AND A FEW SHOWERS STATEWIDE.  
 
GUIDANCE OFFERS MORE VARIANCE AND UNCERTAINTY AT LONGER TIME  
FRAMES, BUT GENERALLY AGREES TO PROGRESS AN AMPLIFIED MID-UPPER  
LEVEL TROUGH AND A DEEP SURFACE LOW TO THE NORTHWEST OF THE STATE  
INTO WEDNESDAY/THURSDAY. A FAVORED COMPOSITE OF BEST CLUSTERED  
GUIDANCE FROM THE LATEST GFS/ECMWF AND GEFS/ECMWF ENSEMBLES OFFERS  
POTENTIAL FOR A PRECIPITATION FOCUSING TRAILING COLD FRONT TO  
REACH THE WESTERN ISLANDS AS VEERING LEAD TRADES RETURN MOISTURE  
OVER THE STATE.  
 
SCHICHTEL  
 

 
 
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