368  
FXHW01 KWNH 281231  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
830 AM EDT SAT OCT 28 2017  
 
VALID 00Z SUN OCT 29 2017 - 00Z SUN NOV 05 2017  
 
SHORTWAVE RIDGING WILL ESTABLISH ITS PRESENCE OVER THE ISLAND  
CHAIN IN BETWEEN A PAIR OF SYSTEMS WHICH HAVE BEEN TRACKING  
THROUGH THE ACTIVE MID-LATITUDE FLOW. THE LEAD SYSTEM IS FORECAST  
TO CUT OFF JUST EAST OF 150W BUT SHOULD GENERALLY REMAIN OUT OF  
THE PICTURE WHEN IT RELATES TO HAWAI`IAN IMPACTS. LOOKING  
UPSTREAM, A MUCH MORE PRONOUNCED UPPER TROUGH WILL BE CROSSING THE  
INTERNATIONAL DATELINE THIS WEEKEND. SOLID AGREEMENT EXISTS IN  
CUTTING OFF THIS SYSTEM AS WELL, GENERALLY IN THE VICINITY OF  
30N/170W ON TUESDAY. GRADUALLY AMPLIFIED FLOW WITHIN THE  
NORTH-CENTRAL PACIFIC WILL DRAW THIS MENTIONED SYSTEM NORTHWARD  
WHICH ALLOWS HEIGHTS TO BUILD OVER THE CENTRAL PACIFIC. TOWARD OF  
NEXT WEEK, MODELS SHOW A BROAD 588-DM RIDGE SETTLING OVER THE  
STATE AS HIGH-AMPLITUDE FLOW ESTABLISHES ITS PRESENCE ACROSS MUCH  
OF THE OCEANIC BASIN. WHILE SOLUTIONS VARY ON DETAILS WITH THE  
UPSTREAM TROUGH, THEY DO NOT SEEM OF SIGNIFICANT CONSEQUENCE TO  
HAWAI`I.  
 
WITH A SHEARING FRONTAL ZONE REMAINING OVER THE BIG ISLAND, THE  
REMNANT AXIS OF LOW-LEVEL CONVERGENCE COULD FOSTER THE DEVELOPMENT  
OF SOME SCATTERED SHOWERS. EVENTUALLY LIGHT WARM ADVECTION WILL  
TAKE SHAPE ACROSS THE REGION WHICH ALLOWS FOR A SHIFT TO A GENERAL  
SOUTH-SOUTHEASTERLY FLOW. THIS ULTIMATELY ALLOWS FOR A NICE SURGE  
OF TROPICAL MOISTURE AS PRECIPITABLE WATER VALUES RISE INTO THE  
1.50 TO 2.00 INCH RANGE BY EARLY NEXT WEEK. BY TUESDAY/WEDNESDAY,  
WIND SPEEDS BEGIN TO PICK UP TO AROUND 10 TO 15 KNOTS AS A FRONTAL  
ZONE APPROACHES FROM THE NORTHWEST. MOST SOLUTIONS FAVOR THE  
ENHANCED SHOWERS TO REMAIN JUST OFFSHORE OF KAUAI. BY THURSDAY  
ONWARD, A SHIFT TO A MORE CLIMATOLOGICAL TRADE WIND REGIME IS  
EXPECTED WITH SPEEDS PICKING UP TOWARD NEXT WEEKEND GIVEN A ROBUST  
SURFACE HIGH SETTING UP OVER THE EASTERN PACIFIC. WINDWARD SHOWERS  
WILL BE LIKELY GIVEN THE RE-ESTABLISHMENT OF THE TRADES.  
 
RUBIN-OSTER  
 

 
 
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