012  
FXHW01 KWNH 301230  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
830 AM EDT MON OCT 30 2017  
 
VALID 00Z TUE OCT 31 2017 - 00Z TUE NOV 07 2017  
 
THE OVERALL SYNOPTIC-SCALE PATTERN WILL FEATURE A REX BLOCK OFF TO  
THE NORTHEAST OF THE HAWAI`IAN CHAIN WHILE BROAD LONGWAVE  
TROUGHING INITIALLY EXTENDS JUST EAST OF THE INTERNATIONAL  
DATELINE. EVENTUALLY A CLOSED UPPER LOW IS FORECAST TO DEVELOP ON  
TUESDAY IN THE PROXIMITY OF 30N/170W WITH THE CYCLONIC CIRCULATION  
EVENTUALLY GETTING LIFTED NORTHWARD TOWARD THE NORTH-CENTRAL  
PACIFIC. AS THIS OCCURS, MID-LEVEL HEIGHTS WILL CONTINUE TO RISE  
DOWNSTREAM ALONG THE LONGITUDE SPANNING HAWAI`I. BY THURSDAY INTO  
THE WEEKEND, MODELS DEPICT A 588-DM CLOSED UPPER HIGH FORMING. SEE  
LITTLE CHANGE IN THIS EVOLVING PATTERN WITH THE ONLY MODEL SPREAD  
BEING WITH SURROUNDING FEATURES WHICH POSE NO THREATS TO THE  
REGION.  
 
AT THE SURFACE, THE INITIAL LIGHTER WINDS ACROSS THE ISLANDS WILL  
GRADUALLY PICK UP IN STRENGTH TODAY AS WARM ADVECTION ENSUES IN  
RESPONSE TO LOWERING HEIGHTS FARTHER UPSTREAM. PRECIPITABLE WATER  
VALUES RESPOND WITH MODEST RISES AS NUMBERS EXCEED 2 INCHES OVER  
THE NORTHERN MOST ISLANDS INCLUDING KAUAI. THIS SHOULD INCREASE  
THE THREAT FOR MODERATE TO LOCALLY HEAVY RAINFALL OVER THESE  
REGIONS BEGINNING TUESDAY AS THE COLD FRONT APPROACHES FROM THE  
NORTHWEST. BY THE FOLLOWING DAY, THE HEAVIER AXIS OF PRECIPITATION  
SHOULD BEGIN TO LIFT BACK TOWARD THE NORTH AS THE PARENT FEATURE  
MIGRATES FURTHER INTO THE MID-LATITUDES. EVENTUALLY SURFACE WINDS  
WILL DIMINISH AS SURFACE GRADIENTS BEGIN TO WEAKEN. ON FRIDAY AND  
THE DAYS FOLLOWING, A ROBUST SURFACE RIDGE BUILDS ACROSS THE  
NORTHEAST PACIFIC ALLOWING FOR A RETURN TO MODERATE TO  
OCCASIONALLY STRONGER TRADE WINDS. MANY SOLUTIONS SHOW THE WINDS  
REACHING THE 25 TO 30 KNOT RANGE THIS WEEKEND AS THE GRADIENT  
FURTHER TIGHTENS. THIS WILL BE ACCOMPANIED BY THE USUAL WINDWARD  
SHOWERS ALTHOUGH THE COVERAGE SHOULD DECREASE SOME BY THE END OF  
THE PERIOD AS OVERALL MOISTURE STARTS TO COME DOWN.  
 
RUBIN-OSTER  
 

 
 
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