501  
FXHW01 KWNH 111210  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
710 AM EST MON DEC 11 2017  
 
VALID 00Z TUE DEC 12 2017 - 00Z TUE DEC 19 2017  
 
COLD FRONT STILL APPEARS ON TRACK TO MOVE ACROSS HAWAI'I TUE/WED  
AS AN UPPER TROUGH AMPLIFIES NORTH OF THE ISLANDS.  
MODELS/ENSEMBLES STILL SHOW GOOD AGREEMENT THAT A PORTION OF THE  
TROUGH WILL CUT OFF INTO AN UPPER LOW JUST EAST OF HAWAI'I WED  
NIGHT/THU AND THEN SLOWLY DRIFT WESTWARD INTO THE WEEKEND. BY  
SUN-MON THE UPPER LOW SHOULD BEGIN TO BECOME ABSORBED INTO ANOTHER  
FULL LATITUDE TROUGH AXIS EXTENDING FROM JUST NORTHWEST OF HAWAI'I  
TO THE GULF OF ALASKA. SUFFICIENT MOISTURE WILL BE ASSOCIATED WITH  
THE FRONTAL PASSAGE TUE/WED TO SUPPORT SCATTERED SHOWERS AND  
PERHAPS EVEN A FEW LOCALIZED AREAS OF HEAVY RAINFALL. THE MORE  
SIGNIFICANT THREAT FOR RAINFALL WILL OCCUR LATE IN THE WEEK AS THE  
UPPER LOW CUTS OFF AND DRIFTS WEST, ALLOWING DEEPER MOISTURE TO BE  
PULLED NORTHWARD ACROSS THE STATE. THUS, EXPECT NUMEROUS SHOWERS  
(AND EVEN SOME THREAT FOR THUNDER GIVEN THE UPPER LOW PASSING  
OVERHEAD) BY FRI-SAT, ESPECIALLY FOCUSED ALONG EAST FACING TERRAIN  
GIVEN EXPECTED LOW-LEVEL EASTERLY FLOW OF 20-25 KT. ECENS QPF  
PROBABILITIES SHOW ABOUT A 20 PERCENT CHANCE FOR EXCEEDING 2  
INCHES OF RAINFALL ACROSS THE BIG ISLAND AND MAUI FOR THE 48-HOUR  
PERIOD ENDING AT 00Z SUN, WITH A 35-45 PERCENT CHANCE FOR  
EXCEEDING 1 INCH - CONTINUING A GRADUAL CLIMB IN THESE  
PROBABILITIES NOTED OVER THE PAST SEVERAL DAYS. THUS, CONFIDENCE  
CONTINUES TO INCREASE IN THE POTENTIAL FOR AT LEAST LOCALLY HEAVY  
RAINFALL ACROSS PORTIONS OF THE BIG ISLAND AND MAUI BY LATE IN THE  
WEEK. AS THE NEXT UPPER TROUGH AMPLIFIES NORTHWEST OF HAWAI'I BY  
EARLY NEXT WEEK, EXPECT A BROAD PLUME OF TROPICAL MOISTURE TO  
CONTINUE STREAMING ACROSS PORTIONS OF HAWAI'I UNTIL THE TROUGH  
AXIS AND ANY SURFACE FRONTAL BOUNDARY CAN CLEAR THE STATE.  
 
RYAN  
 

 
 
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