[Tropical] Tropical Cyclone Discussion

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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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