284 
 WTNT42 KNHC 280910
 TCDAT2
 HURRICANE KATRINA DISCUSSION NUMBER  21
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 5 AM EDT SUN AUG 28 2005
  
 KATRINA CONTINUES TO INTENSIFY AND GROW LARGER.  AN AIR FORCE
 RECONNAISSANCE AIRCRAFT MOST RECENTLY MEASURED A MINIMUM CENTRAL
 PRESSURE OF 935 MB... AND THE WINDS HAVE RESPONDED SIGNIFICANTLY...
 WITH THE MAXIMUM FLIGHT LEVEL WIND OF 137 KT EARLIER THIS MORNING. 
 THIS OBSERVATION ALONG WITH RECENT DVORAK INTENSITY ESTIMATES
 SUPPORT THE ADVISORY INTENSITY OF 125 KT.  ADDITIONALLY...THE
 AIRCRAFT DATA AND SHIP OBSERVATIONS INDICATE THAT THE WIND FIELD
 CONTINUES TO EXPAND.  THE INITIAL AND FORECAST WIND RADII HAVE
 AGAIN BEEN EXPANDED.  ALTHOUGH THE NEW OFFICIAL FORECAST SHOWS NO
 FURTHER EXPANSION OF THE RADII BEFORE LANDFALL...THIS IS CERTAINLY
 POSSIBLE.  DUE TO THE UNCERTAINTY IN BOTH THE TRACK AND SIZE
 FORECASTS...TROPICAL STORM WARNINGS HAVE BEEN EXTENDED BOTH EAST
 AND WEST ALONG THE NORTHERN GULF COAST.  THE INTENSITY FORECAST
 ANTICIPATES THAT KATRINA COULD APPROACH CATEGORY FIVE STATUS PRIOR
 TO LANDFALL.  THE SHIPS GUIDANCE ACTUALLY DOES FORECAST 140 KT AT
 24 HOURS... BUT IT IS ALSO POSSIBLE THAT INTERNAL STRUCTURAL
 CHANGES COULD CAUSE FLUCTUATIONS IN THE INTENSITY... SO THE
 OFFICIAL FORECAST PEAKS AT 135 KT.  WHILE THE DETAILS OF THE
 LANDFALL INTENSITY CANNOT BE NOT KNOWN AT THIS TIME... KATRINA WILL
 BE A VERY DANGEROUS HURRICANE AT LANDFALL.
 
 KATRINA IS MOVING ALONG THE PREVIOUS FORECAST TRACK... JUST A LITTLE
 FASTER NOW WITH AN INITIAL MOTION ESTIMATE OF 290/9.  DYNAMICAL
 MODELS ARE IN TIGHT AGREEMENT ON THE TURN TO THE NORTH DURING THE
 NEXT 24-36 HOURS INTO A WEAKNESS IN THE RIDGE ASSOCIATED WITH A
 LARGE MIDLATITUDE LOW PRESSURE SYSTEM OVER THE NORTHERN UNITED
 STATES AND SOUTHERN CANADA.  THE MODEL CONSENSUS TRACK HAS HARDLY
 MOVED SINCE THE LAST FORECAST CYCLE AND IS VERY CLOSE TO THE
 PREVIOUS OFFICIAL FORECAST...WHICH THE NEW FORECAST BASICALLY JUST
 UPDATES.  THE SPREAD IN THE MODEL TRACKS ALONG THE NORTHERN GULF
 COAST IS AT MOST 90 MILES... SO CONFIDENCE IN THE OFFICIAL FORECAST
 IS RELATIVELY HIGH.  HOWEVER...IT MUST BE EMPHASIZED THAT THE EXACT
 LANDFALL POINT CANNOT BE SPECIFIED AND THAT KATRINA IS A LARGE
 HURRICANE THAT WILL AFFECT A LARGE AREA... BOTH AT THE COAST AND
 WELL INLAND.  PREPARATIONS SHOULD BE RUSHED TO COMPLETION
 THROUGHOUT THE WARNING AREAS.
  
 FORECASTER KNABB
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      28/0900Z 25.4N  87.4W   125 KT
  12HR VT     28/1800Z 26.3N  88.4W   130 KT
  24HR VT     29/0600Z 28.0N  89.4W   135 KT
  36HR VT     29/1800Z 30.0N  89.8W   125 KT
  48HR VT     30/0600Z 32.3N  89.3W    65 KT...INLAND
  72HR VT     31/0600Z 37.5N  86.0W    35 KT...INLAND
  96HR VT     01/0600Z 42.0N  79.0W    30 KT...EXTRATROPICAL
 120HR VT     02/0600Z 47.0N  70.0W    25 KT...EXTRATROPICAL
  
  
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