Hurricane KATE

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TROPICAL STORM KATE DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT TUE SEP 30 2003
 
KATE IS UNDERGOING SOME SIGNIFICANT VERTICAL SHEAR...DUE IN PART TO 
THE CYCLONE SLOWING ITS FORWARD SPEED AND ALSO TURNING MORE
NORTHWARD NOW. CONVECTIVE CLOUD TOPS HAVE WARMED SIGNIFICANTLY AND
THE OVERALL CLOUD PATTERN HAS BECOME QUITE RAGGED IN APPEARANCE.
THERE REMAINS ...HOWEVER...A RATHER WELL-DEFINED LOW-/MID-LEVEL
CIRCULATION AS NOTED IN NIGHTTIME VISIBLE IMAGERY. THE INITIAL
INTENSITY IS LOWERED TO 55 KT BASED ON A CONSENSUS DVORAK SATELLITE
INTENSITY ESTIMATE OF T3.5...OR 55 KT...FROM TAFB...SAB...AND AFWA.
 
THE INITIAL MOTION ESTIMATE IS 015/07...EVEN THOUGH THE PAST 6-HOUR
MOTION WAS 035/10. ALL OF THE GLOBAL MODELS AGREE ON KATE BECOMING
NEARLY STATIONARY WITHIN THE NEXT 12 HOURS...AND THE LAST FEW
SATELLITE POSITION ESTIMATES SUGGEST THAT THIS MAY ALREADY BE
OCCURRING. AFTER THAT...HOWEVER...THERE IS A SIGNIFICANT
BIFURCATION IN THE NHC MODEL GUIDANCE WITH HALF THE MODELS TAKING
KATE EASTWARD...WHILE THE OTHER HALF TAKE THE CYCLONE WESTWARD. THE
UKMET AND MEDIUM AND DEEP BAM MODELS TAKE KATE EASTWARD...WHILE THE
GFS...NOGAPS...CANADIAN...GFDL...AND GFDN MODELS MOVE KATE
WESTWARD. THE UKMET KEEPS KATE AS A RELATIVELY WEAK CYCLONE...WHICH
DOES NOT APPEAR LIKELY GIVEN THE TENACITY WITH WHICH THIS CYCLONE
HAS FOUGHT OFF SOME HOSTILE SHEAR CONDITIONS...INDICATING THAT KATE
IS A VERY DEEP AND WELL-ORGANIZED SYSTEM. AS SUCH...KATE IS
EXPECTED TO SLOW AND THEN TURN WESTWARD BY 24 HOURS AS IS UNDERGOES
SOME BINARY INTERACTION WITH A MID-/UPPER-LEVEL LOW  LOCATED ABOUT
350 NMI WEST OF THE CYCLONE. AS THE UPPER-LOW DROPS SOUTHWARD ...
KATE IS EXPECTED TO TURN WESTWARD UNDER THE INFLUENCE OF INCREASING
DEEP-LAYERED EASTERLY FLOW. THE OFFICIAL FORECAST TRACK IS TO THE
LEFT OF THE PREVIOUS FORECAST TRACK...AND ALSO FASTER AFTER 72
HOURS....WHICH IS SIMILAR TO THE GFDL...GFS AND NOGAPS MODELS.

KATE MAY WEAKEN A LITTLE MORE IN THE NEXT 12 HOURS OR SO AS THE
COMBINATION OF SOUTHWESTERLY FLOW ON THE EAST SIDE OF THE UPPER-LOW
TO THE WEST MAINTAINS SOME SHEAR ON THE SLOW-MOVING CYCLONE.
HOWEVER...BY 24-36 HOURS...THE UPPER-LEVEL FLOW IS FORECAST BY ALL
THE GLOBAL AND REGIONAL MODELS TO BECOME LIGHT TO MODERATE EASTERLY
WHICH WOULD FAVOR ADDITIONAL STRENGTHENING. IN FACT...BY 96 TO 120
HOURS...A SMALL ANTICYCLONE IS FORECAST BY ALL THE MODELS TO RESIDE
NEAR 35N 50W...WHICH WOULD FAVOR EVEN MORE STRENGTHENING THAN WHAT
THE OFFICIAL FORECAST IS INDICATING. THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE SHIPS INTENSITY MODEL THROUGH 72 HOURS
...AND THEN MUCH HIGHER THAN SHIPS BASED ON THE LOWER LATITUDE
FORECAST KEEPING KATE OVER WARMER WATER AND ALSO UNDER LITTLE OR NO
SHEAR CONDITIONS. THE GFDL MODEL IS SIMILAR IN THAT IT BRINGS KATE
UP TO 80-85 KT IN 48-60 HOURS AND THEN HOLDS IT STEADY AFTER THAT.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/0900Z 31.1N  34.7W    55 KT
 12HR VT     30/1800Z 31.9N  34.8W    55 KT
 24HR VT     01/0600Z 32.1N  35.7W    60 KT
 36HR VT     01/1800Z 32.3N  36.6W    65 KT
 48HR VT     02/0600Z 32.4N  38.0W    70 KT
 72HR VT     03/0600Z 32.6N  41.4W    70 KT
 96HR VT     04/0600Z 33.5N  45.5W    70 KT
120HR VT     05/0600Z 35.0N  50.0W    70 KT
 
 
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