687  
FXHW01 KWNH 261219  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
719 AM EST SUN NOV 26 2017  
 
VALID 00Z MON NOV 27 2017 - 00Z MON DEC 04 2017  
   
..HEAVY RAIN LIKELY THIS WEEK
 
 
SURFACE HIGH TO THE NORTH OF THE REGION WILL SLIDE EASTWARD WHICH  
WILL MAINTAIN BREEZY/WINDY TRADES FOR THE NEXT FEW DAYS. LIGHT TO  
SCATTERED WINDWARD/MAUKA SHOWERS ARE EXPECTED TODAY. DEEP MOISTURE  
FROM THE ITCZ WILL SURGE NORTHWARD STARTING LATER TODAY INTO THE  
BIG ISLAND AND MAUI WHICH WILL INCREASE RAIN COVERAGE FROM  
SOUTHEAST TO NORTHWEST.  
 
AN APPROACHING TROUGH FROM NORTHWEST WED/THU IS FORECAST TO DIP  
SOUTHWARD BUT THE MODELS SPLIT ON HOW MUCH TROUGHING TO CARRY  
EASTWARD VS DROP SOUTHWARD. THE GFS HAS MOSTLY MAINTAINED THE  
NORTHERN PORTION AT THE EXPENSE OF THE SOUTHERN WHILE THE  
ECMWF/CANADIAN WERE OPPOSITE. ENSEMBLES STILL SUGGEST SOMETHING  
LIKE THE ECMWF/CANADIAN WHICH THEN TIES INTO HOW A SURFACE LOW  
LIFTS OUT OF THE ITCZ LATE THURSDAY INTO FRIDAY. ECMWF ENSEMBLE  
MEAN AND GEFS MEAN HAVE TRENDED MORE DEFINED WITH THE ECMWF-LIKE  
SCENARIO AND STILL PREFER THIS TO THE GFS SOLUTION (WHICH AT LEAST  
SHOWED A SFC LOW IN RECENT RUNS BUT EITHER WEAKER AND TO THE WEST  
(00Z) OR FARTHER EAST (06Z)). ENSEMBLE PRECIPITABLE WATER PLUMES  
SHOW THE GFS AMONG THE LOWEST 10 PERCENT OF ECMWF/GEFS MEMBERS  
WHILE THE ECMWF WAVERED IN BETWEEN THE MIDDLE TO HIGHEST 10  
PERCENT.  
 
00Z GEFS M-CLIMATE QPF PERCENTILES REMAIN AT OR ABOVE THE 99TH  
PERCENTILE (SOME MAX VALUES AS WELL) FROM ABOUT THURSDAY ONWARD SO  
THE POTENTIAL REMAINS FOR MODEST TO LOCALLY HEAVY RAIN NEXT WEEK,  
PERHAPS SHIFTING FROM THE SOUTHEASTERN ISLANDS TO THE WESTERN  
ISLANDS AS THE PATTERN EVOLVES AND ASSUMING A SURFACE LOW LIFTS  
NORTHWARD TO THE WEST OF THE REGION.  
 
FRACASSO  
 

 
 
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