464  
FXHW01 KWNH 251214  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
714 AM EST THU JAN 25 2018  
 
VALID 00Z FRI JAN 26 2018 - 00Z FRI FEB 02 2018  
 
MEAN TROUGHING ALOFT BECOMING ESTABLISHED OVER OR JUST  
WEST/NORTHWEST OF THE STATE WILL SUPPORT A SERIES OF FRONTAL  
APPROACHES/PASSAGES ALONG WITH PERIODS OF ENHANCED RAINFALL  
POTENTIAL AND WINDS THAT WILL VARY ON A DAY TO DAY BASIS.  
 
FROM LATE THIS WEEK INTO THE WEEKEND THE BIG ISLAND AND VICINITY  
WILL BE ON THE WESTERN PERIPHERY OF ENHANCED MOISTURE AS DENOTED  
BY 1.50" OR GREATER PRECIPITABLE WATER VALUES. EXPECT THE EASTERN  
ISLANDS TO SEE THE BEST CHANCE FOR RAINFALL DURING THIS TIME FRAME  
GIVEN THE COMBINATION OF EAST-SOUTHEASTERLY LOW LEVEL FLOW AND  
SURFACE FRONT CROSSING THE ISLANDS DURING THE WEEKEND. FRONTAL  
PASSAGE WILL BRING A DRIER TREND ALONG WITH A BRIEF PERIOD OF  
NORTHEASTERLY TO EASTERLY WINDS SUNDAY-MONDAY.  
 
AN UPSTREAM SYSTEM WILL BRING ANOTHER FRONT TOWARD THE WESTERN  
ISLANDS BY TUESDAY-WEDNESDAY WITH TIMING DIFFERENCES APPEARING  
FAIRLY TYPICAL FOR A FORECAST 5-6 DAYS OUT IN TIME. DYNAMICS  
ALOFT LOOK STRONGER WITH THIS FRONT VERSUS ITS PREDECESSOR SO THE  
INCREASED RAINFALL POTENTIAL SIGNALED BY MOST MODEL/ENSEMBLE  
GUIDANCE BY MIDWEEK APPEARS REASONABLE. IN ADDITION THIS FRONT  
MAY DECELERATE/STALL IN RESPONSE TO THE APPROACH OF ANOTHER FRONT  
BY THE END OF THE FORECAST PERIOD NEXT THURSDAY. THIS EVOLUTION  
WILL HAVE TO BE MONITORED IN COMING DAYS, WITH SOME DETAIL  
ADJUSTMENTS LIKELY TO OCCUR.  
 
BASED ON CURRENT GUIDANCE SPREAD AN AVERAGE OF THE GFS/ECMWF AND  
THEIR ENSEMBLE MEAN RUNS SHOULD PROVIDE A REASONABLE STARTING  
POINT TO RESOLVE DETAIL DIFFERENCES THROUGH THE FORECAST PERIOD.  
 
RAUSCH  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page