068  
FXHW01 KWNH 251216  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
715 AM EST MON DEC 25 2017  
 
VALID 00Z TUE DEC 26 2017 - 00Z TUE JAN 02 2018  
 
THE DOMINANT SYSTEM OF INTEREST DURING THE PERIOD WILL BE A  
STRONGLY SHARPENING SHORTWAVE THAT WILL APPROACH THE STATE LATER  
TODAY AND TUESDAY, THEN PROGRESS ACROSS THE STATE WEDNESDAY INTO  
THURSDAY AS ENERGY UPSTREAM BRIEFLY SLOWS THE PROGRESS OF THE  
OVERALL TROUGH. THE COMBINATION OF STRONG DYNAMICS ALOFT, WITH  
THE INITIAL SHORTWAVE LIKELY TAKING ON A NEGATIVE TILT, AND  
LEADING COLD FRONT WILL GENERATE A STRONG SOUTHERLY FLOW OF  
MOISTURE AND POTENTIAL FOR SOME STRONG CONVECTION AND/OR HEAVY  
RAINFALL. GUIDANCE IS AGREEABLE IN PRINCIPLE, WITH DIFFERENCES  
GENERALLY WITHIN THE TYPICAL ERROR RANGE FOR THE TIME FRAME OF  
INTEREST.  
 
DRIER AIR WILL MOVE INTO THE REGION FROM NORTHWEST TO SOUTHEAST  
DURING THE LATTER HALF OF THE WEEK. MODELS SUGGEST PRECIPITABLE  
WATER VALUES MAY INCREASE A BIT FOR THE SATURDAY-MONDAY PERIOD BUT  
REMAIN BELOW AVERAGE FOR THE SEASON. AFTER THE UPPER TROUGH  
PASSES BY, MODELS/ENSEMBLES STILL DIFFER ON THE DETAILS BUT AS A  
WHOLE HAVE TRENDED EASTWARD WITH THE LOCATION OF ANY POTENTIAL  
CLOSED LOW COMPARED TO GUIDANCE FROM 24 HOURS AGO. GFS DETAILS  
ALOFT CONTINUE TO RESULT IN ITS RUNS SHOWING A STRONGER INVERTED  
SURFACE TROUGH EAST OF THE STATE VERSUS MOST OTHER GUIDANCE. THUS  
AS HIGH PRESSURE PROGRESSES EASTWARD TO THE NORTH OF THE ISLANDS,  
EXPECT THE TRANSITION FROM NORTHEASTERLY TO MORE EASTERLY TRADES  
TO OCCUR A LITTLE SOONER THAN IN THE GFS. FROM LATE WEEK ONWARD  
ANTICIPATE RELATIVELY LIGHT SHOWER ACTIVITY FOCUSED OVER WINDWARD  
TERRAIN.  
 
RAUSCH  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page