599  
FXHW01 KWNH 190753  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
252 AM EST THU JAN 19 2023  
 
VALID 00Z FRI JAN 20 2023 - 00Z FRI JAN 27 2023  
 
THE MODELS AND ENSEMBLES ARE STILL FAIRLY AGREEABLE WITH THE  
FORECAST INTO TUESDAY-WEDNESDAY, FOLLOWED BY INCREASING SPREAD FOR  
AN UPPER TROUGH THAT DEVELOPS OVER AND NORTH OF THE ISLANDS WITH  
SOME POTENTIAL INFLUENCE ON THE PRECISE SURFACE PATTERN AND WINDS.  
FROM LATE THIS WEEK INTO THE WEEKEND EXPECT THE BEST  
MOISTURE/RAINFALL POTENTIAL TO BE OVER THE NORTHWESTERN ISLANDS,  
WITH AN INITIAL FRONT NEARBY ON THURSDAY WEAKENING AND A BETTER  
DEFINED FRONT REACHING ITS CLOSEST PROXIMITY AROUND LATE  
SATURDAY-EARLY SUNDAY. DURING THE THURSDAY-SATURDAY PERIOD,  
EXPECT LIGHT WINDS WITH LAND/SEA BREEZE INFLUENCE ON SHOWERS  
(THOUGH WITH SOME SOUTHEASTERLY FOCUS FOR THE BIG ISLAND) EARLY TO  
TRANSITION TO STRONGER SOUTHERLY FLOW AHEAD OF THE SECOND FRONT.  
CONSENSUS STILL SHOWS THE FRONT WEAKENING/RETREATING WESTWARD  
AFTER EARLY SUNDAY AS UPPER RIDGING BUILDS OVERHEAD AND EASTERLY  
TRADES BECOME ESTABLISHED. THE NEXT FRONT THAT APPROACHES SHOULD  
MAKE GREATER EASTWARD PROGRESS, CROSSING THE ISLANDS AROUND  
MIDWEEK AND TURNING LOW LEVEL WINDS MORE NORTHEASTERLY OR  
NORTHERLY. THUS FAR THE MODELS ARE NOT SHOWING VERY ANOMALOUS  
MOISTURE WITH THIS LAST FRONT BUT THERE MAY STILL BE SOME LOCALLY  
ENHANCED RAINFALL. THEN THE TERRAIN FOCUS FOR SHOWERS WOULD SHIFT  
WITH THE CHANGE IN WIND DIRECTION. BY NEXT THURSDAY THE MODELS  
AND ENSEMBLE MEMBERS DIVERGE CONSIDERABLY FOR THE AMPLITUDE OF  
UPPER TROUGHING THAT REACHES THE AREA. THE 00Z ECMWF IS A NOTABLE  
EXTREME, AND CHANGE FROM ITS PRIOR RUN, IN BRINGING A FAIRLY DEEP  
UPPER LOW DOWN TO 30N LATITUDE BY LATE NEXT THURSDAY (LEADING INTO  
AN EVEN MORE ANOMALOUS SOUTHWEST DRIFT THEREAFTER). THE RESULTING  
SURFACE REFLECTION IN THE 00Z ECMWF PROMOTES NORTHERLY WINDS  
VERSUS THE PREFERRED REMAINING GUIDANCE THAT SHOWS MOSTLY  
NORTHEASTERLY WINDS.  
 
RAUSCH  
 

 
 
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