818  
FXHW01 KWNH 151151  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
651 AM EST FRI DEC 15 2017  
 
VALID 00Z SAT DEC 16 2017 - 00Z SAT DEC 23 2017  
   
..HEAVY RAIN THREAT NEXT WEEK
 
 
AN UPPER LOW WILL SLOWLY DRIFT WEST-NORTHWESTWARD INTO SATURDAY,  
PASSING JUST NORTH OF MAUI, AND THEN ON SUNDAY THE UPPER LOW IS  
FORECAST TO LIFT NORTHWARD AWAY FROM THE STATE, ALLOWING BRIEF  
RIDGING LATE SUNDAY AND SUNDAY NIGHT.  
 
ON MONDAY, AN UPPER TROUGH APPROACHES FROM THE NORTHWEST, WHICH  
THEN CROSSES THE WESTERN ISLANDS TUE AND SLOWS AS IT CROSSES THE  
EASTERN ISLANDS WED AND THU.  
THERE WAS IMPROVEMENT IN THE TIMING OF THE UPPER TROUGH AMONG THE  
MODELS AND ENSEMBLES WITH GOOD CLUSTERING AMONG THE ECMWF/ECMWF  
ENSEMBLE MEAN AND GFS AND GEFS MEAN. THE PRIMARY DIFFERENCES ARE  
THE PHASING, WITH BOTH THE GFS AND ECMWF SHOWING OCCASIONAL CLOSED  
LOWS EMBEDDED WITHIN THE UPPER TROUGH.  
 
SCATTERED SHOWERS ARE EXPECTED FRIDAY AND SATURDAY ACROSS THE  
ISLANDS, WITH A LITTLE MORE COVERAGE IN THE WESTERN ISLANDS IN  
ADVANCE OF THE TROUGH.  
THE HEAVIEST RAIN ON THE EAST SIDE OF THE UPPER LOW WILL REMAIN  
DISPLACED TO THE NORTHEAST OF THE REGION. LESS COVERAGE IS  
EXPECTED SUNDAY WITH THE UPPER TROUGH DEPARTING. SHOWER COVERAGE  
INCREASES AGAIN TUESDAY AND WEDNESDAY WITH THE UPPER TROUGH  
APPROACHING. WITH THE FETCH OF DEEP TROPICAL MOISTURE, THERE IS  
POTENTIAL  
FOR LOCALLY HEAVY DOWNPOURS. RAINFALL COVERAGE/AMOUNTS WILL  
DECREASE ONCE THE UPPER TROUGH PASSES LATE NEXT WEEK.  
 
PETERSEN  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page