189 
 WTNT44 KNHC 231500
 TCDAT4
  
 HURRICANE IRENE DISCUSSION NUMBER  13
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092011
 1100 AM EDT TUE AUG 23 2011
  
 THE LAST FEW VISIBLE SATELLITE IMAGES SHOW A HINT OF AN EYE... WHILE
 RECENT MICROWAVE DATA SHOW AN EYEWALL THAT IS OPEN TO THE SOUTH.
 THE LATEST SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB WERE 77
 AND 90 KT...RESPECTIVELY...AND SUPPORT MAINTAINING AN INITIAL
 INTENSITY OF 85 KT. THE RECONNAISSANCE AIRCRAFT SCHEDULED TO
 INVESTIGATE IRENE THIS MORNING HAD ISSUES WITH THE ON-BOARD RADAR.
 THIS REQUIRED A CHANGE IN AIRCRAFT AND THE NEW PLANE JUST PASSED
 THROUGH THE CENTER...REPORTING A MINIMUM PRESSURE OF 980 MB...ABOUT
 THE SAME AS DURING THE PREVIOUS MISSION.
  
 A SHEAR ANALYSIS FROM UW-CIMSS SHOWS ABOUT 10-20 KT OF SOUTHWESTERLY
 SHEAR OVER IRENE....AND THE SHIPS GUIDANCE DOES NOT WEAKEN THIS
 SHEAR DURING THE NEXT COUPLE OF DAYS.  AS A RESULT...THE SHIPS/LGEM
 MODELS DO NOT SHOW MUCH STRENGTHENING DURING THAT TIME.  ON THE
 OTHER HAND...THE GFDL/HWRF MODELS ARE MUCH MORE AGGRESSIVE AND MAKE
 IRENE A MAJOR HURRICANE WITHIN 24 HOURS. THE NEW INTENSITY FORECAST
 IS HIGHER THAN THE STATISTICAL GUIDANCE...BUT NOT AS AGGRESSIVE AS
 THE GFDL/HWRF. THE UPDATED FORECAST IS SLIGHTLY BELOW THE PREVIOUS
 ADVISORY.
  
 IRENE HAS BEEN MOVING WEST-NORTHWESTWARD OR 295 DEGREES AT 10 KT. A
 MID/UPPER-LEVEL TROUGH MOVING OVER THE NORTHEASTERN UNITED STATES
 IS EXPECTED TO WEAKEN THE WESTERN PORTION OF THE SUBTROPICAL RIDGE
 DURING THE NEXT DAY OR SO. THIS SHOULD ALLOW IRENE TO TURN
 NORTHWESTWARD WITHIN THE NEXT 24-36 HOURS...AND THE TRACK GUIDANCE
 IS IN EXCELLENT AGREEMENT DURING THE FIRST 48 HOURS. LATER IN THE
 FORECAST PERIOD IRENE IS FORECAST TO TURN NORTHWARD AS IT ROUNDS
 THE WESTERN PORTION OF THE RIDGE. THE SPREAD IN THE GUIDANCE
 INCREASES BY DAY THREE...RANGING FROM THE COASTAL MID-ATLANTIC
 STATES TO WELL OFFSHORE...WITH THE UKMET ALONG THE LEFT SIDE AND
 THE GFS/NOGAPS ALONG THE RIGHT SIDE OF THE GUIDANCE ENVELOPE. THE
 UPDATED TRACK IS CLOSEST TO THE ECMWF AND IS A LITTLE LEFT OF THE
 MULTI-MODEL CONSENSUS. IT IS IMPORTANT TO REMIND USERS NOT TO FOCUS
 ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4 AND 5...SINCE
 THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST TIMES ARE
 200 AND 250 MILES...RESPECTIVELY.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  23/1500Z 20.5N  71.0W   85 KT 100 MPH
  12H  24/0000Z 21.3N  72.3W   90 KT 105 MPH
  24H  24/1200Z 22.3N  73.8W  100 KT 115 MPH
  36H  25/0000Z 23.6N  75.2W  105 KT 120 MPH
  48H  25/1200Z 25.3N  76.5W  110 KT 125 MPH
  72H  26/1200Z 29.2N  77.5W  110 KT 125 MPH
  96H  27/1200Z 33.0N  77.5W  100 KT 115 MPH
 120H  28/1200Z 37.5N  76.0W   65 KT  75 MPH...INLAND
  
 $$
 FORECASTER BROWN