313  
FXHW01 KWNH 170744  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
344 AM EDT WED MAY 17 2023  
 
VALID 00Z THU MAY 18 2023 - 00Z THU MAY 25 2023  
 
WEDNESDAY WILL BEGIN A WETTER SHIFT TO THE WEATHER PATTERN OVER  
HAWAII AS AN UPPER TROUGH WEST OF THE STATE MOVES EASTWARD. WINDS  
TURNING MORE SOUTHERLY AHEAD OF THE UPPER TROUGH WILL HELP DRAW IN  
ANOMALOUSLY HIGH TROPICAL MOISTURE (LIKELY ABOVE THE 95TH  
PERCENTILE FOR PRECIPITABLE WATER). THUS, ENHANCED RAINFALL TOTALS  
ARE LIKELY ACROSS THE WESTERN ISLANDS IN PARTICULAR ON THURSDAY  
AND FRIDAY AS SHOWERS INCREASE IN COVERAGE AND INTENSITY, AND THE  
LOCAL WEATHER FORECAST OFFICE HAS A FLOOD WATCH IN PLACE FOR THIS  
ACTIVITY. THE UPPER TROUGH MOVING IN COULD LESSEN OR ELIMINATE THE  
TYPICAL INVERSION, PROVIDING INSTABILITY FOR SOME POSSIBLE  
THUNDERSTORMS. SOME SHOWERS COULD MAKE IT TO THE EASTERN PART OF  
THE STATE BUT OVERALL THE BEST CHANCES FOR HEAVY RAIN WILL BE IN  
KAUAI/OAHU. SHOWER COVERAGE SHOULD GRADUALLY DECREASE THROUGH THE  
WEEKEND AS THE WEAKENING UPPER TROUGH MOVES AWAY AND IS REPLACED  
BY AN UPPER RIDGE. THIS WILL SHIFT THE MOISTURE PLUME WEST OF THE  
STATE NEXT WEEK WHILE SURFACE HIGHS BUILD TO THE NORTHEAST AND  
NORTHWEST, CREATING A MORE TYPICAL AND DRIER EASTERLY TRADE WIND  
PATTERN.  
 
TATE  
 

 
 
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