[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 022051
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST FRI SEP 02 2011

KATIA REMAINS A HURRICANE THIS AFTERNOON...BUT IS STRUGGLING WITH
MODERATE VERTICAL SHEAR.  A 1718Z TRMM SATELLITE PASS INDICATED
THAT THE SURFACE CENTER IS TILTED SOUTHWARD FROM THE MID-LEVEL
CIRCULATION. DATA-T NUMBERS FROM BOTH TAFB AND SAB DECREASED
TO 3.5...THOUGH THE CURRENT INTENSITY NUMBERS REMAIN AT 4.0 ON THE
DVORAK SCALE.  THE INITIAL INTENSITY IS KEPT AT 65 KT...A MINIMAL
HURRICANE...THOUGH IT IS QUITE POSSIBLE THAT KATIA IS SLIGHTLY
WEAKER.

THE HURRICANE IS MOVING TOWARD THE NORTHWEST AT ABOUT 10 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 ABOUT THE SAME RATE OF SPEED.
ALL OF THE RELIABLE GUIDANCE IS IN EXCELLENT AGREEMENT...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.  THE TRACK FORECAST IS SHIFTED
SLIGHTLY TO THE LEFT COMPARED TO THE PREVIOUS ADVISORY AND IS BASED
UPON THE CONSENSUS OF THE GLOBAL AND HURRICANE MODELS EXCEPT THE
UKMET MODEL. IT IS STILL TOO EARLY TO SAY WHETHER KATIA WILL
DIRECTLY IMPACT THE UNITED STATES.

THE HURRICANE FACES A RELATIVELY HOSTILE ENVIRONMENT WITH SOUTHWEST
VERTICAL SHEAR OF 15-20 KT LIKELY FOR THE NEXT DAY OR TWO.  BEYOND
48 HOURS...THE SHEAR AS SHOWN IN THE GLOBAL MODELS IS ANTICIPATED
TO DECREASE SOME.  HOWEVER...THE THERMODYNAMICS AT THAT TIME MAY
NOT BE IDEAL AS LOW HUMIDITIES AND A MORE STABLE ENVIRONMENT IS
ANTICIPATED.  THE INTENSITY PREDICTION IS MOST SIMILAR TO A BLEND
OF THE SHIPS/LGEM/HWRF MODELS AS WELL AS THE NEW IV15 INTENSITY
CONSENSUS FROM THE HURRICANE FORECAST IMPROVEMENT PROGRAM.

THE TROPICAL-STORM WIND RADII WERE ADJUSTED OUTWARD SOME BASED UPON
A 1334Z ASCAT PASS.

FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 18.4N  53.5W   65 KT  75 MPH
 12H  03/0600Z 19.0N  54.5W   65 KT  75 MPH
 24H  03/1800Z 19.9N  55.8W   70 KT  80 MPH
 36H  04/0600Z 20.9N  57.1W   75 KT  85 MPH
 48H  04/1800Z 21.9N  58.7W   80 KT  90 MPH
 72H  05/1800Z 24.0N  62.0W   90 KT 105 MPH
 96H  06/1800Z 26.0N  65.0W   95 KT 110 MPH
120H  07/1800Z 27.5N  68.0W   95 KT 110 MPH

$$
FORECASTER LANDSEA/STEWART

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