164  
FXHW01 KWNH 141219  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
718 AM EST WED FEB 14 2018  
 
VALID 00Z THU FEB 15 2018 - 00Z THU FEB 22 2018  
 
LATEST GUIDANCE MAINTAINS FAIRLY GOOD CONTINUITY FROM YESTERDAY,  
WITH A MEAN TROUGH ALOFT SUPPORTING UNSETTLED WEATHER WHILE  
PREVENTING ESTABLISHMENT OF TRADE FLOW AS A CORRESPONDING SURFACE  
TROUGH PREVAILS OVER THE ISLANDS FOR MOST OF THE PERIOD.  
 
MODEL AND ENSEMBLE CONSENSUS STILL SHOWS A DEEP UPPER LOW  
INITIALLY NORTHWEST OF THE STATE TRACKING NORTH OF KAUAI BY  
THURSDAY AND THEN OPENING UP/LIFTING NORTHWARD AS UPSTREAM ENERGY  
APPROACHES. EXPECT THIS EVOLUTION TO SUPPORT A PERIOD OF ENHANCED  
FOCUS OF DEEP MOISTURE WITH AN AXIS OF HEAVY RAINFALL POTENTIAL  
AND POSSIBLE EMBEDDED CONVECTION DRIFTING FROM WEST TO EAST ACROSS  
THE STATE DURING MID-LATE WEEK. MOISTURE AND RAINFALL WILL LIKELY  
LINGER OVER/NEAR THE BIG ISLAND AS INITIAL DYNAMICS DEPART AND THE  
MEAN TROUGH BEGINS TO RELOAD.  
 
GUIDANCE IS CONSISTENT IN DEPICTING THE CLOSURE OF ANOTHER UPPER  
LOW BY SUNDAY-MONDAY WITHIN THE RELOADING UPPER TROUGH, WITH A LOW  
TRACK OVER OR VERY CLOSE TO THE ISLANDS. AS THIS OCCURS  
MOISTURE/RAINFALL MAY RETURN WESTWARD FOR A TIME AND A WEAK LOW  
MAY FORM ALONG THE NORTH-SOUTH SURFACE TROUGH OVER THE AREA. AS  
WAS THE CASE YESTERDAY, THE 00Z CMC UPPER LOW TRACK IS A LITTLE  
SOUTH OF MOST OTHER SOLUTIONS THOUGH ITS MEAN IS SIMILAR. ALSO  
THE 00Z/06Z GFS CONTINUE TO SHOW A DEEPER FEATURE THAN OTHER  
GUIDANCE WITH A HIGHER PERCENTAGE OF 00Z GEFS MEMBERS THAN ECMWF  
MEMBERS OFFERING SUPPORT FOR THE GFS DEPTH. ONLY ONE FARTHER  
NORTH CMC ENSEMBLE MEMBER HAS A 570 DM HEIGHT CONTOUR. BASED ON  
THE CURRENT ARRAY OF GUIDANCE WOULD PREFER AN UPPER LOW DEPTH AT  
LEAST HALFWAY TOWARD THE 00Z ECMWF AND GEFS/ECMWF MEANS VERSUS THE  
DEEPER GFS. MOST GUIDANCE HAS THIS UPPER LOW WEAKENING AND/OR  
LIFTING AWAY NEXT WEDNESDAY BUT PRESENCE OF A STRONG RIDGE OVER  
THE MID-LATITUDE PACIFIC MAKES IT MORE DIFFICULT TO DETERMINE ITS  
DIRECTION OF MOTION. EXPECT THE CIRCULATION AROUND THE UPPER LOW  
TO BRING IN SOMEWHAT DRIER AIR FROM THE WEST BY TUESDAY-WEDNESDAY  
THOUGH THE FEATURE WILL LIKELY MAINTAIN SOME INSTABILITY OVER THE  
AREA INTO TUESDAY.  
 
RAUSCH  
 

 
 
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