[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 021454
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST FRI SEP 02 2011

THE CONVECTIVE DEPICTION OF KATIA HAS IMPROVED THIS MORNING AS BOTH
MICROWAVE IMAGERY FROM SSMIS AND CONVENTIONAL VISIBLE SATELLITE
IMAGERY INDICATE THAT AN EYE MAY BE FORMING.  BECAUSE OF THE
IMPROVED STRUCTURE...BOTH TAFB AND SAB DVORAK CLASSIFICATIONS CAME
IN AT A 4.0...OR 65 KT...AS DID A 1053Z CIMSS AMSU INTENSITY
ESTIMATE.  THUS KATIA HAS REGAINED HURRICANE STATUS.

THE HURRICANE IS MOVING TOWARD THE WEST-NORTHWEST AT ABOUT 12
KT...AS IT IS BEING ADVECTED AROUND THE SOUTHWEST PERIPHERY OF A
DEEP-LAYER RIDGE.  KATIA SHOULD MOVE TOWARD THE WEST-NORTHWEST OR
NORTHWEST FOR THE NEXT FEW DAYS AT A SLIGHTLY SLOWER RATE OF SPEED.
ALL OF THE RELIABLE GUIDANCE...WITH THE EXCEPTION OF THE UKMET WHICH
HAS A MUCH MORE EQUATORWARD SOLUTION DUE TO A SHORT-WAVE TROUGH OFF
OF THE U.S. EAST COAST LIFTING OUT TO THE NORTHEAST MORE QUICKLY...
IS IN EXCELLENT AGREEMENT.  THE TRACK FORECAST IS VERY SIMILAR TO
THE PREVIOUS ADVISORY AND THE CONSENSUS OF THE GLOBAL AND HURRICANE
MODELS LESS THE UKMET MODEL.

DESPITE BECOMING A HURRICANE AGAIN...KATIA FACES A RELATIVELY
HOSTILE ENVIRONMENT WITH SOUTHWEST VERTICAL SHEAR OF 15-20 KT
SUGGESTED FOR THE NEXT DAY OR TWO.  BEYOND 48 HOURS...THE SHEAR
FROM THE GLOBAL MODELS IS ANTICIPATED TO DECREASE...BUT THE
THERMODYNAMICS MAY NOT BE IDEAL WITH LOW HUMIDITIES AND A MORE
STABLE ENVIRONMENT ANTICIPATED.  SOME OF THE UPPER-LEVEL
TEMPERATURE INCREASES ANALYZED IN THE SHIPS/LGEM STATISTICAL
MODELS...HOWEVER...MAY BE SPURIOUS...AS THE STRONGER VORTEX FROM
THE GFS MAY BE THE CAUSE OF THESE VALUES RATHER THAN THE
ENVIRONMENT.  THUS THE SHIPS/LGEM GUIDANCE MAY BE TOO LOW AT DAYS
THREE TO FIVE. THE INTENSITY PREDICTION IS SLIGHTLY LOWER THAN A
SHIPS/LGEM/HWRF BLEND BUT HIGHER THAN THE PREVIOUS ADVISORY DURING
THE NEXT TWO DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 17.5N  52.4W   65 KT  75 MPH
 12H  03/0000Z 18.6N  53.8W   65 KT  75 MPH
 24H  03/1200Z 19.6N  55.2W   70 KT  80 MPH
 36H  04/0000Z 20.6N  56.4W   75 KT  85 MPH
 48H  04/1200Z 21.7N  57.9W   80 KT  90 MPH
 72H  05/1200Z 24.0N  61.0W   90 KT 105 MPH
 96H  06/1200Z 26.0N  64.0W   95 KT 110 MPH
120H  07/1200Z 27.0N  67.0W  100 KT 115 MPH

$$
FORECASTER LANDSEA/STEWART



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