783  
FXHW01 KWNH 101221  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
820 AM EDT TUE OCT 10 2017  
 
VALID 00Z WED OCT 11 2017 - 00Z WED OCT 18 2017  
 
THE WEATHER PATTERN ACROSS THE HAWAII DOMAIN DURING THE SHORT  
RANGE PERIOD THROUGH THURSDAY WILL CONSIST OF A GRADUALLY  
WEAKENING INVERTED SURFACE TROUGH SLOWING TRACKING WESTWARD ALONG  
WITH A WEAK UPPER LEVEL TROUGH. THIS IS FORECAST TO TRANSITION TO  
A MORE ZONAL FLOW PATTERN BY THE WEEKEND AND BEYOND AS A LARGE  
SURFACE HIGH SETTLES SOUTHWARD FROM 50 DEGREES NORTH TO 35 DEGREES  
NORTH BY THE END OF THE FORECAST PERIOD, BECOMING ESTABLISHED  
NORTH OF THE ISLANDS AND STRENGTHENING THE EASTERLY TRADE WINDS  
OWING TO THE TIGHTER PRESSURE GRADIENT TO THE NORTH. BOTH THE  
GEFS AND EC MEAN INDICATE THE POTENTIAL FOR A WEAK POSITIVELY  
TILTED 500MB TROUGH DURING THE SECOND HALF OF THE FORECAST PERIOD,  
WITH STRONG UPPER LEVEL RIDGING NORTHWEST OF THE STATE. WHILE  
GREATER DIFFERENCES EXIST IN THE MORE PROGRESSIVE FLOW PATTERN  
ACROSS THE NORTHERN PACIFIC, THE MODELS ARE IN DECENT AGREEMENT AT  
THE LOWER LATITUDES ON THE SYNOPTIC SCALE.  
 
IN TERMS OF EXPECTED SENSIBLE WEATHER, SHOWER ACTIVITY IS EXPECTED  
TO BE LOCALLY ENHANCED ON THE FAVORED WINDWARD TERRAIN ALONG WITH  
GUSTY EASTERLY WINDS. THE SHORT TERM PORTION OF THE FORECAST IS  
EXPECTED TO BE THE DRIEST. BY EARLY NEXT WEEK, PWS WILL LIKELY  
INCREASE TO NEAR 2 INCHES AS THE AFOREMENTIONED UPPER TROUGH  
ADVECTS MOISTURE TOWARDS THE NORTH, AND PRECIPITATION CHANCES WILL  
LIKELY INCREASE AS A RESULT, ESPECIALLY ACROSS THE EASTERN PARTS  
OF THE ISLANDS.  
 
D. HAMRICK  
 

 
 
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