277  
FXHW01 KWNH 301226  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
726 AM EST THU NOV 30 2017  
 
VALID 00Z FRI DEC 01 2017 - 00Z FRI DEC 08 2017  
   
..A HEAVY PRECIPITATION THREAT
 
 
SURFACE HIGH PRESSURE BRIDGING TO THE NORTH OF THE STATE IS ACTING  
TO REINFORCE A PATTERN SUPPORTING BREEZY/WINDY TRADES THROUGH THE  
WEEKEND. DEEP TROPICAL MOISTURE WITH PRECIPITATBLE WATER VALUES  
NEAR 2" HAS LIFTED INTO THE STATE AS A MID-UPPER LEVEL SHORTWAVE  
TROUGH AND ASSOCIATED HEIGHT FALLS DIGS OVER AND JUST TO THE NORTH  
THEN NORTHEAST OF THE STATE. THIS IS INDUCING LEAD INVERTED  
SURFACE TROUGHING THROUGH THE STATE WHOSE SOUTHEASTWARD VEERED  
TRADES ON ITS EAST SIDE ARE ADVECTING DEEP TROPICAL MOISTURE TO  
FUEL LOCALLY HEAVY RAINFALL.  
 
A FLASH FLOOD WARNING IS CURRENTLY IN EFFECT IN KAUAI. FLASH FLOOD  
WATCHES REMAIN IN EFFECT OVER THE BIG ISLAND AND MAUI AND A WINTER  
STORM ADVISORY IS ALSO IN EFFECT FOR THE SUMMITS OF MAUNA LOA AND  
MAUNA KEA FOR LINGERING SNOW. HIGH SURF AND SMALL CRAFT ADVISORIES  
ARE ALSO IN EFFECT. THE HEAVY PRECIPITATION THREAT WILL DIMINISH  
OVER THE WEEKEND WITH LEAD FRONTAL PASSAGE.  
 
A SECOND AND MORE AMPLIFIED MID-UPPER LEVEL SHORTWAVE TROUGH  
PASSAGE ALONG/NORTH OF THE STATE INTO TUESDAY AND WEDNESDAY AND  
ASSOCIATED FRONTAL TRACK WILL FURTHER FILTER DRIER AIR ACROSS THE  
STATE IN A PATTERN WITH DISRUPTED TRADES. MODEL AND ENSEMBLE  
FORECAST SPREAD AND UNCERTAINTY IS ABOUT AT AVERAGE LEVELS  
OVERALL. THE MOST NOTABLE MASS FIELD DIFFERENCES ARE EVIDENT IN  
THE TUESDAY TO THURSDAY TIMEFRAME AND CONCERN THE AMPLITUDE OF THE  
THIS FEATURE. THE NAVGEM IS THE LEAST AMPIFIED. THE CANADIAN IS  
THE MOST AMPLIFIED AND ACTUALLY CARVES OUT A SEPARATED SOUTHERN  
STREAM CLOSED LOW JUST TO THE NORTHEAST OF THE STATE  
WEDNESDAY-NEXT THURSDAY THAT COULD OFFER A MORE SIGNIFICANT  
WEATHER THREAT RENEWAL. THE GFS AND ECMWF ARE CLOSER TO THE CENTER  
OF THE FORECAST ENVELOPE AND HAVE THE MOST ENSEMBLE SUPPORT.  
PREFER A SOLUTION CLOSER TO THE GFS/ECMWF, BUT WILL CONTINUE TO  
MONITOR UPSTREAM MID-UPPER RIDGE AMPLITUDE OVER THE WEST-CENTRAL  
PACIFIC FOR FUTURE SIGNS OF POTENTIALLY DEEPER DOWNSTREAM ENERGY  
DIGGING TOWARD THE ISLANDS NEXT WEEK.  
 
SCHICHTEL  
 

 
 
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