971 
 WTNT44 KNHC 250319
 TCDAT4
  
 TROPICAL STORM ISAAC DISCUSSION NUMBER  16
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
 1100 PM EDT FRI AUG 24 2012
  
 SATELLITE IMAGERY AND RECONNAISSANCE AIRCRAFT DATA INDICATE THAT THE
 CIRCULATION AND CONVECTIVE ORGANIZATION OF ISAAC HAS CONTINUED TO
 IMPROVE SINCE THE PREVIOUS ADVISORY. INFRARED AND MICROWAVE
 SATELLITE IMAGERY SUGGEST THAT AN EYE IS FORMING...AND THIS IS THE
 BASIS FOR INCREASING THE INTENSITY TO 60 KT. 
  
 THE INITIAL MOTION ESTIMATE IS 315/12 BASED ON RECON AND MICROWAVE
 FIXES. ALTHOUGH THE TRACK FORCAST WAS ADJUSTED SLIGHTLY TO THE
 RIGHT THROUGH 48 HOURS...NO OTHER SIGNIFICANT CHANGES WERE MADE TO
 THE PREVIOUS ADVISORY TRACK. RECENT UPPER-AIR DATA AND NOAA G-IV
 AIRCRAFT DROPSONDE DATA INDICATE THE TROUGH THAT HAS CREATED THE
 BREAK IN THE SUBTROPICAL RIDGE ACROSS FLORIDA HAS SHIFTED TO A
 POSITION JUST EAST OF THE FLORIDA PENINSULA. THE 18Z GFS MODEL...
 WHICH SHIFTED TO THE RIGHT OF ITS 12Z TRACK...CAPTURED THIS FARTHER
 EAST POSITION...WHEREAS THE 18Z UKMET AND 12Z ECMWF KEPT THE TROUGH
 ACROSS THE WESTERN FLORIDA PENINSULA VALID AT 00Z THIS EVENING.
 BASED ON THE GFS VERIFYING BETTER THAN THE OTHER MODELS AT 00Z THIS
 EVENING...THE NHC TRACK HAS BEEN SHIFTED A LITTLE TO THE RIGHT.
 AFTER 48 HOURS...THE RIDGE IS EXPECTED TO BUILD BACK WESTWARD
 ACROSS FLORIDA AND KEEPING ISAAC ON A MOSTLY NORTHWESTWARD HEADING
 ACROSS THE EASTERN AND NORTH-CENTRAL GULF MEXICO. THE OFFICIAL
 FORECAST TRACK IS CLOSE TO THE CONSENSUS MODELS TVCA AND TV15
 THROUGH 48 HOURS...AND THEN IS A LITTLE TO THE RIGHT OF THOSE
 MODELS AFTER THAT.
 
 WITH THE INNER CORE CONVECTION IMPROVING...THERE IS STILL THE
 POSSIBILITY THAT ISAAC COULD REACH HURRICANE INTENSITY BEFORE
 REACHING HAITI TONIGHT. THE INTENSITY FROM 12-24 HOURS WILL BE
 DETERMINED BY THE AMOUNT OF LAND INTERACTION WITH HAITI AND EASTERN
 CUBA. AFTER THAT...THE SLIGHT EASTWARD SHIFT IN THE FORECAST TRACK
 IS ENOUGH TO PLACE ISAAC OVER WATER LONGER THAN WHAT WAS INDICATED
 IN THE PREVIOUS INTENSITY FORECAST REQUIRED AN INCREASE IN THE
 INTENSITY FORECAST. THE EASTWARD TRACK SHIFT AND A LARGER INITIAL
 AND FORECAST WIND FIELD TO THE NORTH ARE WHAT NECESSITATED THE
 CHANGES IN THE WATCHES AND WARNINGS FOR FLORIDA.
  
 IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK DUE TO THE
 UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
 AREA OF TROPICAL-STORM-FORCE WINDS ASSOCIATED WITH IT.  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  25/0300Z 17.7N  72.5W   60 KT  70 MPH
  12H  25/1200Z 19.4N  74.1W   50 KT  60 MPH
  24H  26/0000Z 21.7N  76.7W   50 KT  60 MPH
  36H  26/1200Z 23.4N  79.4W   55 KT  65 MPH
  48H  27/0000Z 24.9N  81.6W   60 KT  70 MPH
  72H  28/0000Z 27.1N  84.6W   70 KT  80 MPH
  96H  29/0000Z 30.0N  86.5W   80 KT  90 MPH
 120H  30/0000Z 32.5N  86.5W   40 KT  45 MPH...INLAND
  
 $$
 FORECASTER STEWART