255  
FXHW01 KWNH 051228  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
727 AM EST MON FEB 05 2018  
 
VALID 00Z TUE FEB 06 2018 - 00Z TUE FEB 13 2018  
   
..LOCALLY HEAVY RAIN POSSIBLE IN THE SHORT RANGE
 
 
AS OF 12Z MONDAY, A SURFACE COLD FRONT IS CURRENTLY MOVING THROUGH  
THE NORTHWEST ISLANDS WITH SCATTERED SHOWERS AND EMBEDDED  
HEAVIER/STEADIER RAIN AND SOME THUNDERSTORMS. WAVES OF LOW  
PRESSURE WILL RIDE ALONG THE FRONT AS IT SLOWLY MAKES IS WAY DOWN  
THE ISLAND CHAIN OVER THE NEXT COUPLE OF DAYS. WITH AVAILABLE  
MOISTURE WELL ABOVE AVERAGE (1.50-1.75" PRECIPITABLE WATER OR  
ABOUT +2 STANDARD DEVIATIONS) FLASH FLOODING IS POSSIBLE IN SOME  
LOCATIONS. COLD AIR ALOFT WILL SUPPORT SNOW AT THE BIG ISLAND  
SUMMITS.  
 
MODELS/ENSEMBLES SHOW THE COLD FRONT EXITING PAST THE BIG ISLAND  
LATE WEDNESDAY OR EARLY THURSDAY AS THE UPPER TROUGH FINALLY  
SWINGS THROUGH. TIMING WILL DEPEND ON THE EVOLUTION OF THE  
EMBEDDED SURFACE WAVES. NORTHWESTERLY UPPER FLOW WILL FOLLOW IN  
THE WAKE OF THE FROPA AS SURFACE WINDS VEER TO NORTHWESTERLY  
BEHIND THE FRONT THEN QUICKLY TO NORTHERLY/NORTHEASTERLY. A  
SHOWERY AND BREEZY PATTERN FOR THE ISLANDS WILL FOLLOW LATER IN  
THE WEEK INTO THE WEEKEND WITH PRECIPITABLE WATER VALUES GENERALLY  
UNDER ONE INCH. 00Z GFS/ECMWF BLENDED SOLUTION SHOULD SUFFICE  
THROUGH THE PERIOD, WHICH WOULD BE NEAR THE 00Z ECMWF ENSEMBLE  
MEAN. BY NEXT MONDAY, SOME MODELS/ENSEMBLES SHOW A MOISTURE PLUME  
FROM THE EAST TO PUSH WESTWARD INTO THE REGION. THIS MAY HELP TO  
EXPAND PRECIPITATION AHEAD OF ANOTHER SIGNIFICANT TROUGH NEAR 165W  
BY 00Z TUE FEB 13, PER THE ENSEMBLES.  
 
FRACASSO  
 

 
 
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