543 
 WTPA45 PHFO 101445
 TCDCP5
 
 HURRICANE HILDA DISCUSSION NUMBER  19
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP102015
 500 AM HST MON AUG 10 2015
  
 LATEST SUBJECTIVE AND OBJECTIVE DVORAK SATELLITE INTENSITY
 ESTIMATES RANGE FROM 4.5/77 KT TO 5.0/90 KT. GIVEN THE FACT THAT
 HILDA/S SATELLITE REPRESENTATION HAS DEGRADED ONLY MARGINALLY
 OVER THE PAST 6 HOURS...THE INITIAL INTENSITY FOR THIS ADVISORY HAS
 BEEN LOWERED SLIGHTLY TO 80 KT. ANOTHER FLIGHT INTO HILDA WILL BE
 CONDUCTED BY THE U.S. 53RD WEATHER RECONNAISSANCE SQUADRON LATER
 THIS MORNING. 
 
 THE INITIAL MOTION VECTOR FOR THIS ADVISORY IS 300/08 KT...AS HILDA 
 CONTINUES TO ROUND THE WESTERN EDGE OF A DEEP LAYER RIDGE CENTERED 
 TO THE DISTANT EAST. HILDA IS EXPECTED TO GAIN LATITUDE OVER THE 
 NEXT COUPLE OF DAYS AS IT ROUNDS THE RIDGE...BUT THE FORWARD SPEED 
 IS FORECAST TO DIMINISH AS THE STEERING FLOW WEAKENS TODAY AND 
 TOMORROW. AS HILDA MOVES NORTH OF THE RIDGE AXIS...IT WILL ENCOUNTER 
 INCREASING WESTERLY WINDS ALOFT...ASSOCIATED WITH THE SUBTROPICAL 
 JET STREAM. IN THE LATER PERIODS THE FORECAST ANTICIPATES THAT A 
 MUCH WEAKER AND SHALLOWER HILDA WILL BEGIN TO MOVE TOWARD THE 
 WEST-NORTHWEST WITH A GRADUAL INCREASE IN FORWARD SPEED AS IT IS 
 STEERED BY THE LOW-LEVEL TRADE WIND FLOW. 
 
 THE 0600Z RUN OF THE GFS OFFERED A DRAMATICALLY DIFFERENT TRACK AND 
 INTENSITY SOLUTION THAN PREVIOUS RUNS...WITH A MUCH WEAKER HILDA 
 MOVING NEARLY DUE WEST OVER THE NEXT 3 DAYS AND PASSING WELL SOUTH
 OF THE BIG ISLAND BY TUESDAY NIGHT OR WEDNESDAY. THIS CONTRADICTS
 ECMWF GUIDANCE...WHICH SHOWS A FAIRLY WEAK HILDA MOVING NORTHWEST 
 OVER WINDWARD WATERS OF THE HAWAIIAN ISLANDS BEFORE EVENTUALLY 
 MOVING WEST NEAR KAUAI TOWARDS THE END OF THE WEEK. THIS RECENT 
 DIVERGENCE IN SOLUTIONS FROM SOME OF THE MORE RELIABLE TRACK MODELS 
 IS LIKELY DUE TO DIFFERENCES IN THE DEPTH OF THE FORECAST 
 CIRCULATION...AND LEADS TO DECREASED CONFIDENCE IN THE OFFICIAL 
 TRACK FORECAST. WITH THE SOMEWHAT DRAMATIC CHANGES NOTED IN RECENT 
 MODEL RUNS...THE UPDATED TRACK FORECAST OFFERS LITTLE CHANGE FROM 
 THE PREVIOUS. 
 
 THE INTENSITY FORECAST ALSO CONTAINS LITTLE SIGNIFICANT CHANGE FROM
 THE PREVIOUS...WITH STRONG VERTICAL WIND SHEAR LEADING TO A
 SIGNIFICANT WEAKENING OF THE CYCLONE THROUGH THE FORECAST PERIOD.
 THE WEAKENING TREND IN THE OFFICIAL FORECAST IS NOT AS RAPID AS
 INDICATED BY SHIPS...BUT STILL ANTICIPATES THAT HILDA WILL WEAKEN TO
 A TROPICAL STORM ON TUESDAY...SIMILAR TO THE IVCN CONSENSUS.  
 
 ALTHOUGH THE CURRENT FORECAST BRINGS HILDA NEAR THE BIG ISLAND AS A 
 TROPICAL DEPRESSION LATER THIS WEEK...UNCERTAINTY REMAINS AS TO THE
 EVENTUAL IMPACTS THAT MAY BE FELT IN THE HAWAIIAN ISLANDS. INTERESTS 
 IN HAWAII SHOULD CLOSELY MONITOR THE PROGRESS OF HILDA...AND A 
 TROPICAL STORM WATCH MAY BE REQUIRED FOR THE BIG ISLAND LATER TODAY 
 OR TONIGHT. IT IS IMPORTANT NOT TO FOCUS TOO CLOSELY ON THE EXACT 
 TRACK AND INTENSITY FORECASTS BECAUSE AVERAGE INTENSITY ERRORS ARE 
 NEAR 35 MPH ON DAY 5...AND AVERAGE TRACK ERRORS ARE NEAR 175 MILES. 
 IN ADDITION...THE HAZARDS OF A TROPICAL CYCLONE CAN EXTEND OVER A 
 BROAD AREA AWAY FROM THE CENTER. 
   
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  10/1500Z 16.2N 149.8W   80 KT  90 MPH
  12H  11/0000Z 16.8N 150.8W   70 KT  80 MPH
  24H  11/1200Z 17.3N 151.6W   60 KT  70 MPH
  36H  12/0000Z 17.8N 152.3W   45 KT  50 MPH
  48H  12/1200Z 18.4N 153.2W   40 KT  45 MPH
  72H  13/1200Z 19.0N 154.6W   30 KT  35 MPH
  96H  14/1200Z 19.5N 156.0W   30 KT  35 MPH
 120H  15/1200Z 20.0N 158.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
  
 $$
 
 FORECASTER BIRCHARD