HURRICANE ISELLE DISCUSSION NUMBER 23 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014 500 PM HST TUE AUG 05 2014 ISELLE/S SATELLITE APPEARANCE CONTINUES TO DEGRADE AS THE SYSTEM IS WEAKENING IN THE FACE OF 10 TO 15 KT SOUTH-SOUTHWESTERLY SHEAR... BASED ON THE LATEST UW-CIMSS ANALYSIS AND SHIPS GUIDANCE. THE EYE IS BECOMING INCREASINGLY DIFFICULT TO FIND AS IT BECOMES CLOUD-FILLED... AND THE INNER CORE HAS BEEN SIGNIFICANTLY DISRUPTED OVER THE PAST 6 TO 12 HOURS. DVORAK CURRENT INTENSITY ESTIMATES ARE 5.0/90 KT... WHILE FINAL-T NUMBERS INDICATE 4.0/65 KT. BASED ON A BLEND OF THESE ESTIMATES...THE CURRENT INTENSITY HAS BEEN LOWERED TO 85 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS PRESENTLY ENROUTE TO INVESTIGATE ISELLE...AND IS EXPECTED TO PROVIDE GROUND TRUTH FOR THE NEXT ADVISORY CYCLE. FOR NOW...A RECENT ASCAT PASS LED TO SOME MINOR ADJUSTMENTS TO THE TROPICAL STORM FORCE WIND RADII. ISELLE HAS BEEN ACCELERATING TOWARD THE WEST-NORTHWEST TODAY...WITH THE CURRENT MOTION ESTIMATE 295/11 KT. THIS ACCELERATION SHOULD ABATE AFTER 36 HOURS...WITH SOME SLOWING IN THE FORWARD MOTION AND A TURN TOWARD THE WEST LATE IN THE FORECAST PERIOD AS THE SYSTEM BECOMES INCREASINGLY SHALLOW. FORECAST TRACK GUIDANCE REMAINS CONSISTENT AND FAIRLY TIGHTLY CLUSTERED...THUS THE LATEST FORECAST FOLLOWS THE PREVIOUS CLOSELY. ISELLE IS STILL EXPECTED TO PASS NEAR OR OVER THE HAWAIIAN ISLANDS IN 48-72 HOURS. RECENT IMAGERY SHOWS WHAT APPEARS TO BE IMPROVING OUTFLOW IN THE NORTHWEST SEMICIRCLE...AND RESTRICTED OUTFLOW ON THE SOUTH SIDE... ASSOCIATED WITH A SHARP UPPER-LEVEL TROUGH NEAR 143W/144W. THIS TROUGH IS OUTLINED NICELY BY DATA RECENTLY RECEIVED BY THE NOAA G-IV AIRCRAFT...WHICH HAS BEEN SAMPLING THE NEAR-STORM ENVIRONMENT THROUGHOUT THE DAY. SOME RELAXING OF THE SHEAR OVER THE NEXT 12 TO 36 HOURS IS ANTICIPATED AS THE TROUGH WEAKENS...AND A RIDGE ALOFT OVER THE MAIN HAWAIIAN ISLANDS SHIFTS WEST. THE INTENSITY FORECAST RESPONDS BY INDICATING STEADY WEAKENING IN THE SHORT TERM...AND A SLOWER RATE OF WEAKENING THEREAFTER. THE UPDATED INTENSITY FORECAST FOLLOWS THE TRENDS DEPICTED BY THE SHIPS/LGEM/IVCN GUIDANCE...BUT REMAINS SLOWER...WITH SHIPS GUIDANCE WEAKENING ISELLE TO A TROPICAL STORM IN 18 HOURS. IT IS IMPORTANT FOR PEOPLE IN THE MAIN HAWAIIAN ISLANDS NOT TO FOCUS TOO CLOSELY ON THE EXACT FORECAST TRACK OF ISELLE. WITH AN AVERAGE 48 HOUR TRACK ERROR OF APPROXIMATELY 80 MILES...IT IS STILL TOO SOON TO SAY WITH MUCH CERTAINTY WHICH ISLANDS WOULD BE MOST LIKELY TO EXPERIENCE THE WORST WEATHER...AND EVERYONE SHOULD BE PREPARED FOR THE POSSIBILITY OF DIRECT IMPACTS FROM ISELLE. IT IS ALSO IMPORTANT TO KEEP IN MIND THAT SIGNIFICANT IMPACTS FROM TROPICAL CYCLONES CAN EXTEND WELL AWAY FROM THE CENTER. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 16.8N 141.6W 85 KT 100 MPH 12H 06/1200Z 17.3N 143.6W 75 KT 85 MPH 24H 07/0000Z 18.0N 146.8W 65 KT 75 MPH 36H 07/1200Z 18.7N 150.1W 60 KT 70 MPH 48H 08/0000Z 19.3N 153.2W 55 KT 65 MPH 72H 09/0000Z 20.7N 158.7W 45 KT 50 MPH 96H 10/0000Z 21.5N 164.0W 40 KT 45 MPH 120H 11/0000Z 22.0N 168.0W 35 KT 40 MPH
Posted on: Wed, 06 Aug 2014 03:33:58 +0000
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