750  
FXHW01 KWNH 251207  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
707 AM EST SAT NOV 25 2017  
 
VALID 00Z SUN NOV 26 2017 - 00Z SUN DEC 03 2017  
   
..HEAVY RAIN PROBABLE NEXT WEEK
 
 
SURFACE HIGH TO THE NNW OF THE REGION WILL SLIDE SOUTHEASTWARD  
THEN EASTWARD ALONG 32-33N WHICH WILL MAINTAIN BREEZY/WINDY TRADES  
THROUGH ABOUT TUESDAY. LIGHT TO SCATTERED WINDWARD/MAUKA SHOWERS  
ARE EXPECTED WITH ONLY SOME SPILLOVER TO LEEWARD AREAS POSSIBLE AS  
THE OVERALL AIR MASS REMAINS DRY TODAY.  
 
FROM LATE SUNDAY ONWARD, DEEP MOISTURE FROM THE ITCZ WILL SURGE  
NORTHWARD INTO THE BIG ISLAND AND MAUI WHICH WILL INCREASE RAIN  
COVERAGE FROM SOUTHEAST TO NORTHWEST OVER THE ISLAND CHAIN.  
ANOTHER APPROACHING TROUGH FROM NORTHWEST WED/THU IS FORECAST TO  
DIP SOUTHWARD BUT THE MODELS SPLIT ON HOW FAR EAST -- THE 00Z  
ECMWF/CANADIAN WERE FARTHER EAST THAN THE GFS. THE ENSEMBLE  
SYSTEMS SUPPORT SOMETHING IN BETWEEN THE GFS/ECMWF ON FRIDAY BUT  
CLOSER TO THE ECMWF BY NEXT SATURDAY (THOUGH NOT AS DEEP). PREFER  
A SOLUTION IN BETWEEN THE 00Z ECMWF AND THE 00Z GEFS MEAN. THIS  
WOULD NOT YET NECESSARILY FAVOR A DEFINED SURFACE LOW LIFTING  
NORTHWARD JUST WEST OF THE ISLANDS LATER NEXT WEEK BUT EVEN THE  
ENSEMBLES DO SHOW AN INVERTED TROUGH AXIS BULGING NORTHWARD AROUND  
163W NEXT SATURDAY. 00Z GEFS M-CLIMATE QPF PERCENTILES REMAIN AT  
THE 99TH PERCENTILE FROM MIDWEEK 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.  
 
FRACASSO  
 

 
 
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