[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 281454
TCDAT2
HURRICANE KATRINA DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SUN AUG 28 2005

THE AIR FORCE HURRICANE HUNTERS JUST MEASURED A 166 KT FLIGHT LEVEL
WIND IN THE NORTHEAST EYEWALL...WHICH REQUIRES AN ADDITIONAL UPWARD
ADJUSTMENT OF THE CURRENT INTENSITY TO 150 KT.  A DROP IN THE EYE
GAVE A CENTRAL PRESSURE OF 907 MB.  KATRINA IS COMPARABLE IN
INTENSITY TO HURRICANE CAMILLE OF 1969...ONLY LARGER.  GPS
DROPSONDE DATA FROM THE NOAA G-IV MISSION EARLIER TODAY SHOWED
KATRINA'S INTENSE CYCLONIC CIRCULATION EXTENDING THROUGH THE 200 MB
LEVEL...WITH THE FLOW SPIRALING ANTICYLONICALLY OUTWARD IN A
WELL-DEVELOPED UPPER-LEVEL OUTFLOW PATTERN BEYOND A COUPLE HUNDRED
N MI FROM THE CENTER.  FLUCTUATIONS IN STRENGTH...DUE TO INTERNAL
STRUCTURAL CHANGES...ARE LIKELY PRIOR TO LANDFALL.  HURRICANES
RARELY SUSTAIN SUCH EXTREME WINDS FOR MUCH TIME.  HOWEVER WE SEE
NO OBVIOUS LARGE-SCALE EFFECTS TO CAUSE A SUBSTANTIAL WEAKENING THE
SYSTEM...AND IT IS EXPECTED THAT THE HURRICANE WILL BE OF CATEGORY
4 OR 5 INTENSITY WHEN IT REACHES THE COAST.

THERE IS NO CHANGE TO THE TRACK FORECAST.  KATRINA SHOULD GRADUALLY
TURN TOWARD THE NORTH...INTO A WEAKNESS IN THE SUBTROPICAL RIDGE
ASSOCIATED WITH A LARGE MID-LATITUDE CYCLONE OVER THE NORTHERN
UNITED STATES AND SOUTHERN CANADA.  THE OFFICIAL FORECAST TRACK IS
ABOUT IN THE MIDDLE OF THE DYNAMICAL GUIDANCE MODELS...WHICH ARE
RATHER TIGHTLY CLUSTERED.  RECALLING THAT THE AVERAGE NHC 24-HOUR
TRACK FORECAST ERROR IS ABOUT 80 N MI...THE ACTUAL LANDFALL POINT
COULD STILL BE ANYWHERE FROM SOUTHEASTERN LOUISIANA TO THE
MISSISSIPPI COAST.  ALSO...WE MUST CONTINUE TO STRESS THAT THE
HURRICANE IS NOT JUST A POINT ON THE MAP...BECAUSE DESTRUCTIVE
WINDS...TORRENTIAL RAINS...STORM SURGE...AND DANGEROUS WAVES EXTEND
WELL AWAY FROM THE EYE.  IT IS IMPOSSIBLE TO SPECIFY WHICH COUNTY
OR PARISH WILL EXPERIENCE THE WORST WEATHER.

THIS ADVISORY SHOWS AN ADDITIONAL EXPANSION OF THE WIND FIELD OVER
THE EASTERN SEMICIRCLE BASED ON AIRCRAFT AND SURFACE OBSERVATIONS.
HURRICANE FORCE WINDS ARE FORECAST TO SPREAD AT LEAST 150 N MI
INLAND ALONG THE PATH OF KATRINA.  CONSULT INLAND WARNINGS ISSUED
BY NATIONAL WEATHER SERVICE FORECAST OFFICES.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      28/1500Z 26.0N  88.1W   150 KT
 12HR VT     29/0000Z 27.2N  88.9W   145 KT
 24HR VT     29/1200Z 29.1N  89.6W   140 KT
 36HR VT     30/0000Z 31.4N  89.5W    85 KT...INLAND
 48HR VT     30/1200Z 34.5N  88.5W    45 KT...INLAND
 72HR VT     31/1200Z 40.0N  84.0W    30 KT...INLAND
 96HR VT     01/1200Z 45.0N  77.0W    25 KT...EXTRATROPICAL
120HR VT     02/1200Z 52.0N  69.0W    25 KT...EXTRATROPICAL


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