976  
FXHW01 KWNH 061202  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
701 AM EST TUE MAR 06 2018  
 
VALID 00Z WED MAR 07 2018 - 00Z WED MAR 14 2018  
 
A WEAK COLD FRONT MOVING SOUTHWARD THROUGH THE AREA TODAY IS  
EXPECTED TO STALL OUT TONIGHT NEAR THE BIG ISLAND AS SHORT WAVE  
ENERGY DIVES INTO AND ELONGATES THE POSITIVELY-TILTED TROUGH NORTH  
OF THE STATE. MOISTURE AND INSTABILITY ALONG THE BOUNDARY IS NOT  
TOO IMPRESSIVE, SO EXPECT MOSTLY SCATTERED WINDWARD SHOWERS TO  
PERSIST THROUGH THURSDAY. FARTHER NORTH BEHIND THE FRONT, DRY AND  
SLIGHTLY COOLER AIR WILL PUSH ACROSS MOST OF THE ISLAND CHAIN,  
KEEPING ANY SHOWER ACTIVITY ISOLATED AND LIGHT. DURING FRIDAY, AN  
AMPLIFYING POLAR STREAM SYSTEM WILL KICK OUT THE ELONGATED TROUGH  
AND ALLOW THE FRONT TO PASS FULLY SOUTH OF ALL ISLANDS. HIGH  
PRESSURE BUILDING IN FROM THE NORTHWEST WILL MAINTAIN MOSTLY DRY  
CONDITIONS AT LEAST THROUGH THE WEEKEND, THOUGH TRADES WILL BE ON  
THE BRISK SIDE AND GRADUALLY SHIFT FROM A NORTHEASTERLY TO MORE  
EASTERLY DIRECTION BY THE END OF THE WEEKEND.  
 
THE MAIN FORECAST PROBLEM ARISES LATE IN THE PERIOD. THE MODELS  
ALL GENERALLY SHOW THE UPPER LOW CURRENTLY JUST WEST OF THE  
DATELINE AND NORTH OF 30N DRIFTING SOUTHWARD INTO THE SUBTROPICAL  
STREAM OVER THE NEXT FEW DAYS, THEN PUSHING EASTWARD TOWARD THE  
STATE EARLY NEXT WEEK. THE MAIN DIFFERENCES AMONG THE MODELS IS  
TIMING...WITH THE GFS QUICKEST ADVANCING IT EASTWARD (AND ALSO  
OVERALL THE STRONGEST SOLUTION), WHILE THE ECMWF IS SLOWEST. AT  
THIS TIME, THE CANADIAN AND NAVGEM ARE LEANING TOWARD THE FASTER  
SOLUTION, SO BASED ON MODEL CONSENSUS, WOULD TEND TO DISCOUNT THE  
SLOWER ECMWF (AND ITS ENSEMBLES) AT THIS TIME. AS THIS SYSTEM  
APPROACHES, IT WILL LIFT ABUNDANT TROPICAL MOISTURE ACROSS THE  
STATE FROM SOUTHWEST TO NORTHEAST MONDAY-TUESDAY. WIDESPREAD  
SHOWERS ARE LIKELY ACROSS MUCH OF THE STATE BY TUESDAY,  
POTENTIALLY FOCUSING OVER THE NORTHERN ISLANDS ALONG A WEAK FRONT  
EXTENDING WESTWARD FROM A SYSTEM APPROACHING THE MAINLAND.  
 
KLEIN  
 

 
 
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