666 
 WTNT44 KNHC 241450
 TCDAT4
  
 HURRICANE IRENE DISCUSSION NUMBER  17
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092011
 1100 AM EDT WED AUG 24 2011
  
 IRENE HAS CONTINUED TO STRENGTHEN THIS MORNING.  THE EYE HAS BECOME
 MORE DISTINCT IN SATELLITE IMAGERY AND IT IS SURROUNDED BY CLOUD
 TOPS COLDER THAN -70 DEGREES CELSIUS.  BOTH AIR FORCE AND NOAA
 HURRICANE HUNTER AIRCRAFT HAVE BEEN INVESTIGATING IRENE THIS
 MORNING.  THE AIR FORCE PLANE MEASURED A PEAK 700 MB FLIGHT-LEVEL
 WIND OF 112 KT JUST BEFORE 1200 UTC...AND THIS SUPPORTED THE
 UPGRADE TO A 100-KT CATEGORY THREE HURRICANE AT THAT TIME.  SINCE
 THAT TIME THE NOAA AIRCRAFT REPORTED 115 KT AT 750 MB.  THE
 PRESSURE HAS REMAINED AROUND 956 MB...AND THE INITIAL INTENSITY
 ESTIMATE REMAINS 100 KT.
  
 THE OUTFLOW HAS BECOME WELL ESTABLISHED OVER THE HURRICANE AND IRENE
 WILL BE MOVING OVER SEA SURFACE TEMPERATURES OF AROUND 29 DEGREES
 CELSIUS DURING THE NEXT 24-36 HOURS.  THESE ENVIRONMENTAL FACTORS
 FAVOR ADDITIONAL INTENSIFICATION AND THE NEW INTENSITY FORECAST
 CALLS FOR IRENE TO REACH CATEGORY FOUR STRENGTH WITHIN 24 HOURS. 
 AFTER THAT TIME...SOME FLUCTUATIONS IN WIND SPEEDS ARE LIKELY DUE
 TO EYEWALL REPLACEMENTS.  THE UW-CIMSS OBJECTIVE SECONDARY EYEWALL
 FORMATION TECHNIQUE SHOWS A VERY HIGH LIKELIHOOD OF THAT OCCURRING
 DURING THE NEXT 48 HOURS.  SOUTHWESTERLY SHEAR IS EXPECTED TO
 GRADUALLY INCREASE AND THE HURRICANE WILL BE MOVING OVER
 SIGNIFICANTLY COLDER WATERS BY 96 HOURS.  THIS SHOULD RESULT IN
 GRADUAL WEAKENING...HOWEVER IRENE IS FORECAST TO REMAIN A LARGE AND
 POWERFUL HURRICANE DURING THE NEXT 5 DAYS.
  
 AIRCRAFT FIXES DURING THE PAST 12 HOURS INDICATE THAT IRENE HAS MADE
 THE EXPECTED TURN TOWARD THE NORTHWEST...WITH AN INITIAL MOTION OF
 305/10. THERE IS NO CHANGE TO THE TRACK FORECAST REASONING AND THE
 MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT FOR THE FIRST 2-3
 DAYS. AFTER THAT TIME...THERE IS SOME QUESTION AS TO WHETHER OR NOT
 IRENE CONTINUES ON A NORTH-NORTHEAST HEADING OR TURNS BACK TOWARD
 THE NORTH AHEAD OF A MID-LATITUDE TROUGH APPROACHING THE GREAT
 LAKES REGION. THE GFDL AND HWRF MODELS REMAIN ALONG THE WEST SIDE
 OF THE GUIDANCE ENVELOPE AND SHOW A TRACK OVER OR VERY CLOSE TO THE
 MID-ATLANTIC COAST. THE UKMET AND NOGAPS ARE ALONG THE EASTERN SIDE
 AND KEEP THE CORE OF THE HURRICANE WELL OFFSHORE. GIVEN THE TYPICAL
 MODEL AND OFFICIAL TRACK ERRORS...BOTH SCENARIOS ARE VIABLE OPTIONS
 AT THIS TIME...AND USERS ARE ONCE AGAIN REMINDED NOT TO FOCUS ON
 SPECIFIC FORECAST POINTS THREE TO FIVE DAYS DOWNSTREAM. THE TVCA
 CONSENSUS AND THE EXPERIMENTAL HURRICANE FORECAST IMPROVEMENT
 PROJECT CONSENSUS WERE RELATIVELY CLOSE TO THE PREVIOUS NHC
 FORECAST. THE UPDATED NHC TRACK HAS BEEN NUDGED EASTWARD AT 96 AND
 120 HOURS AND LIES BETWEEN THOSE TWO CONSENSUS AIDS.
  
  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  24/1500Z 22.4N  73.9W  100 KT 115 MPH
  12H  25/0000Z 23.4N  74.8W  110 KT 125 MPH
  24H  25/1200Z 25.1N  76.1W  115 KT 135 MPH
  36H  26/0000Z 27.2N  76.9W  115 KT 135 MPH
  48H  26/1200Z 29.3N  77.2W  110 KT 125 MPH
  72H  27/1200Z 33.2N  76.2W  100 KT 115 MPH
  96H  28/1200Z 38.5N  73.5W   85 KT 100 MPH
 120H  29/1200Z 45.0N  69.5W   70 KT  80 MPH...INLAND
  
 $$
 FORECASTER BROWN