292 
 WTNT44 KNHC 252102
 TCDAT4
  
 TROPICAL STORM ISAAC DISCUSSION NUMBER  19
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
 500 PM EDT SAT AUG 25 2012
 
 THE CENTER OF ISAAC IS CURRENTLY MOVING ALONG THE NORTH COAST OF
 EASTERN CUBA.  THE SATELLITE APPEARANCE IS SOMEWHAT DISORGANIZED...
 WITH THE MAIN CONVECTIVE MASS 50 N MI OR MORE EAST OF THE LOW-LEVEL
 CENTER.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS
 REPORTED 850 MB FLIGHT-LEVEL WINDS OF 56 KT TO THE NORTHEAST OF THE
 CENTER...WITH RELIABLE-LOOKING SFMR SURFACE WIND DATA NEAR 50 KT. 
 BASED ON THIS...THE INITIAL INTENSITY REMAINS 50 KT.  THE CENTRAL
 PRESSURE OF 997 MB IS BASED ON A COMBINATION OF AIRCRAFT DATA AND
 CUBAN SURFACE OBSERVATIONS.
 
 THE INITIAL MOTION IS NOW 310/18.  ISAAC IS CURRENTLY PART OF A
 LARGE LOW/MID-LEVEL LOW PRESSURE SYSTEM COVERING THE NORTHWESTERN
 CARIBBEAN SEA AND THE ADJACENT LAND AND OCEAN AREAS.  THIS LOW
 PRESSURE AREA HAS A SECOND VORTICITY CENTER BETWEEN JAMAICA AND THE
 CAYMAN ISLANDS...AND FOR THE NEXT 24-36 HR ISAAC AND THIS CENTER
 WILL LIKELY ROTATE AROUND EACH OTHER.  BASED ON THIS EXPECTATION...
 THE FORECAST TRACK SHOWS ISAAC MOVING NORTHWESTWARD FOR 12 HR OR
 SO...FOLLOWED BY A TURN TOWARD THE WEST-NORTHWEST.  IT IS POSSIBLE
 THE STORM COULD MAKE A SHARPER TURN THAN FORECAST...AS THE UKMET IS
 SHOWING AN ALMOST DUE WEST MOTION BETWEEN THE FLORIDA KEYS AND CUBA
 NEAR THE 36 HR POINT.  THE EARLY PART OF THE FORECAST TRACK IS
 SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST...BUT STILL
 LIES TO THE RIGHT OF THE CONSENSUS MODELS AND THE BULK OF THE
 DYNAMICAL MODELS.  AFTER 36 HR...ISAAC SHOULD BREAK FREE OF OR
 ABSORB THE REST OF THE LOW...WITH THE SUBTROPICAL RIDGE TO THE EAST
 BECOMING THE DOMINANT STEERING INFLUENCE.  THIS SHOULD ALLOW THE
 STORM TO GRADUALLY TURN TOWARD THE NORTHWEST AND NORTH OVER THE
 EASTERN AND NORTHERN GULF OF MEXICO...WITH AN EVENTUAL LANDFALL
 ALONG THE NORTHERN GULF COAST IN 72-96 HR.  WHERE THIS MIGHT OCCUR
 IS STILL RATHER UNCERTAIN...WITH THE TRACK GUIDANCE SPREAD BETWEEN
 SOUTHEASTERN LOUISIANA AND THE CENTRAL FLORIDA PANHANDLE.  THIS PART
 OF THE TRACK FORECAST LIES IN THE CENTER OF THE GUIDANCE ENVELOPE
 NEAR THE CONSENSUS MODELS AND IS SIMILAR TO THE PREVIOUS FORECAST.
 
 A COMBINATION OF LIGHT WESTERLY VERTICAL WIND SHEAR AND LAND
 INTERACTION SHOULD AT LEAST SLOW INTENSIFICATION FOR THE NEXT 12
 HR.  AFTER THAT...THE SHEAR SHOULD DIMINISH WHILE THE CYCLONE
 REACHES OPEN WATER.  THIS SHOULD ALLOW ISAAC TO GRADUALLY STRENGTHEN
 INTO A HURRICANE NEAR THE FLORIDA KEYS OR OVER THE SOUTHEASTERN
 GULF OF MEXICO.  THE NEW INTENSITY FORECAST IS SIMILAR TO THE
 PREVIOUS FORECAST AND IS NEAR OR A LITTLE ABOVE THE INTENSITY
 CONSENSUS.  IT SHOULD BE NOTED THAT THE GLOBAL MODELS ARE
 FORECASTING A VERY FAVORABLE PATTERN OF UPPER-LEVEL WINDS OVER THE
 NORTHERN GULF OF MEXICO BY 72 HR.  SHOULD THIS VERIFY AND SHOULD
 ISAAC ESTABLISH AN INNER CORE...THE CYCLONE COULD BE SIGNIFICANTLY
 STRONGER THAN CURRENTLY FORECAST.
  
 IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC 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  25/2100Z 21.3N  76.0W   50 KT  60 MPH
  12H  26/0600Z 22.6N  78.0W   55 KT  65 MPH
  24H  26/1800Z 24.1N  80.6W   60 KT  70 MPH
  36H  27/0600Z 25.2N  82.7W   65 KT  75 MPH
  48H  27/1800Z 26.5N  84.3W   75 KT  85 MPH
  72H  28/1800Z 29.0N  86.0W   85 KT 100 MPH
  96H  29/1800Z 31.5N  86.0W   55 KT  65 MPH...INLAND
 120H  30/1800Z 33.5N  85.5W   25 KT  30 MPH...INLAND
  
 $$
 FORECASTER BEVEN