747  
FXHW01 KWNH 131354  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
853 AM EST WED DEC 13 2017  
 
VALID 00Z THU DEC 14 2017 - 00Z THU DEC 21 2017  
 
A COLD FRONT IS CURRENTLY MOVING THROUGH HAWAI'I AND WILL BRING  
SCATTERED SHOWERS TO THE REGION. AN UPPER TROUGH TO THE  
NORTH/NORTHEAST WILL FORM AN UPPER LOW AROUND 151W BY TOMORROW AND  
THEN SLOWLY DRIFT WEST-NORTHWESTWARD INTO THE WEEKEND, JUST TO THE  
NORTH OF HAWAI'I. BY SUNDAY THE UPPER LOW SHOULD LIFT NORTHWARD  
AND BECOME ABSORBED INTO A A TROUGH AXIS TO THE NORTH. THAT TROUGH  
MAY CLOSE OFF AN UPPER LOW ON ITS SOUTHWEST TAIL JUST TO THE NORTH  
OR NORTHWEST OF THE REGION NEXT TUESDAY. 00Z ECMWF/CANADIAN WERE  
PREFERRED WITH THEIR HANDLING OF THE CLOSED LOW - A WEAKER ONE  
NEAR 24N/160W AND A STRONGER ONE AROUND 37N/150W BY 00Z/20 RATHER  
THAN JUST ONE PER THE 00Z-06Z GFS.  
 
BEHIND THE FRONT TODAY, BREEZY NORTHWEST WINDS WILL BRING IN DRIER  
AND COOLER AIR AND VEER TO THE NORTH AND NORTHEAST TOMORROW WHEN  
WINDS MAY EXCEED 30 KTS WITH HIGHER GUSTS. AS THE CLOSED LOW  
APPROACHES FROM THE EAST, MOISTURE WILL WRAP BACK AROUND THE  
SURFACE LOW FROM THE NORTH BUT THE HEAVIEST RAIN ON THE EAST SIDE  
OF THE UPPER LOW WILL REMAIN DISPLACED TO THE NORTHEAST OF THE  
REGION.  
 
THE NEXT UPPER TROUGH OR UPPER LOW NEXT WEEK HAS THE POTENTIAL FOR  
MUCH MORE PRECIPITATION GIVEN THE LOCATION TO THE WEST OF THE  
REGION. 00Z ECMWF INDICATES THE POTENTIAL FOR SEVERAL INCHES OF  
RAIN OVER SOME OF THE ISLANDS WHILE THE GFS WAS DRIER GIVEN ITS  
LACK OF A DEFINED FEATURE. 00Z ECMWF ENSEMBLES SHOW A PROBABILITY  
OF AT LEAST AN INCH OF PRECIPITATION EXCEEDING 30% IN THE 72 HRS  
ENDING 00Z/21. AGAIN, PREFER A SOLUTION NEAR THE 00Z CANADIAN AND  
ECMWF.  
 
FRACASSO  
 

 
 
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