[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 040250
TCDAT2

TROPICAL STORM KATIA DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST SAT SEP 03 2011

ONCE AGAIN TONIGHT...THERE IS AN INCREASE IN ORGANIZATION OF THE
CLOUD PATTERN WITH THE FORMATION OF A ROUND CENTRAL DENSE OVERCAST
AND A BETTER DEFINED OUTFLOW IN CONVENTIONAL IR IMAGES. I HAVE BEEN
LUCKY ENOUGH TO HAVE SEVERAL MICROWAVE PASSES OVER KATIA TONIGHT.
THESE DATA SHOW A MUCH BETTER ORGANIZED INNER CORE STRUCTURE THAN
IN EARLIER PASSES...BUT THE CIRCULAR RING OF CONVECTION
REPRESENTING THE MID-LEVEL EYE FEATURE CONTINUES TO BE DISPLACED TO
THE NORTH OF THE LOW-LEVEL CENTER DUE TO SHEAR. THIS SUGGESTS THAT
THE CYCLONE MIGHT NOT BE AS WELL ORGANIZED AS IT SEEMS IN
CONVENTIONAL IMAGERY.  HAVING SAID THAT...THE INITIAL INTENSITY HAS
BEEN KEPT AT 60 KNOTS BASED ON A BLEND OF THE LATEST DVORAK
T-NUMBERS.  AS STATED IN THE PREVIOUS ADVISORY...KATIA COULD REACH
HURRICANE STATUS AGAIN AT ANY TIME...AND SINCE THE SHEAR SHOULD
BEGIN TO RELAX IN ABOUT 12 TO 24 HOURS ACCORDING TO THE SHIPS
MODEL...A GRADUAL INTENSIFICATION IS INDICATED IN THE OFFICIAL
FORECAST.

SINCE THE OVERALL STEERING PATTERN HAS NOT CHANGED...THERE IS NOT
TOO MUCH TO ADD TO THE DISCUSSION.  KATIA CONTINUES TO MOVE TOWARD
THE NORTHWEST OR 305 DEGREES AT 9 KNOTS AROUND THE SOUTHERN EDGE OF
THE SUBTROPICAL RIDGE. GUIDANCE HAS BEEN SHIFTING SLIGHTLY EASTWARD
OR WESTWARD DEPENDING ON HOW EACH MODEL REPRESENTS THE MID-LEVEL
TROUGH OVER THE EASTERN UNITED STATES IN EACH RUN.  IT INTERESTING
TO NOTE THAT TONIGHT...THE GFS DEFINES THE EASTERN SIDE OF THE
GUIDANCE ENVELOPE AND THE ECMWF THE WESTERN EDGE. THE OFFICIAL
FORECAST IS A THE MIDDLE OF THESE TWO EXTREME SOLUTIONS. IN
GENERAL...MODEL SOLUTIONS ARE TO KEEP KATIA ON A TRACK BETWEEN THE
WEST-NORTHWEST AND NORTHWEST FOR THE NEXT 3 TO 4 DAYS AND THEN TURN
THE CYCLONE MORE TO THE NORTH THEREAFTER.

NOAA BUOY 41044...LOCATED A LITTLE MORE THAN 100 N MI TO THE
NORTHWEST OF KATIA RECENTLY REPORTED WINDS OF 33 KNOTS AND 18-FOOT
WAVES.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 20.3N  57.4W   60 KT  70 MPH
 12H  04/1200Z 21.0N  58.6W   65 KT  75 MPH
 24H  05/0000Z 22.3N  60.3W   65 KT  75 MPH
 36H  05/1200Z 23.5N  62.0W   70 KT  80 MPH
 48H  06/0000Z 24.5N  63.5W   75 KT  85 MPH
 72H  07/0000Z 27.0N  67.0W   85 KT 100 MPH
 96H  08/0000Z 29.1N  70.0W   90 KT 105 MPH
120H  09/0000Z 32.0N  71.0W   85 KT 100 MPH

$$
FORECASTER AVILA


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