[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 311435
TCDAT2

TROPICAL STORM KATIA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST WED AUG 31 2011

KATIA REMAINS A WELL-ORGANIZED TROPICAL CYCLONE WITH DISTINCT
BANDING FEATURES AND A DEVELOPING CENTRAL DENSE OVERCAST.  DVORAK
CLASSIFICATIONS ARE T3.5 FROM BOTH AGENCIES AND THE CURRENT
INTENSITY IS HELD AT 55 KT.  THE SYSTEM HAS A WELL-DEFINED
UPPER-LEVEL OUTFLOW PATTERN.  AT THE MOMENT...IT DOES NOT APPEAR
THAT THE DRY AIR ADJACENT TO THE STORM IS BEING ENTRAINED INTO THE
CIRCULATION.  THE SHIPS MODEL INDICATES THAT VERTICAL SHEAR WILL BE
WEAK FOR THE NEXT DAY OR TWO WHICH SHOULD FAVOR STRENGTHENING AT
LEAST FOR THE EARLIER PART OF THE FORECAST PERIOD.  A LARGE
UPPER-LEVEL LOW TO THE NORTHWEST OF KATIA COULD PLAY A ROLE IN THE
INTENSITY OF THE TROPICAL CYCLONE IN THE LATTER PART OF THE
FORECAST PERIOD.  AS NOTED EARLIER...SOME OF THE GLOBAL MODELS
SUGGEST THAT THIS LOW COULD PRODUCE INCREASING SOUTHWESTERLY SHEAR
IN 4 TO 5 DAYS WHICH WOULD INHIBIT INTENSIFICATION.  THE OFFICIAL
INTENSITY FORECAST IS THE SAME AS THAT FROM THE PREVIOUS ADVISORY
AND IS SLIGHTLY ABOVE THE NUMERICAL CONSENSUS.

KATIA CONTINUES TO MOVE SWIFTLY TOWARD THE WEST-NORTHWEST OR 285/18
TO THE SOUTH OF A MID-TROPOSPHERIC SUBTROPICAL ANTICYCLONE.  THE
DYNAMICAL GUIDANCE IS IN RATHER GOOD AGREEMENT ON A CONTINUATION OF
THIS WEST-NORTHWESTWARD TRACK FOR THE NEXT COUPLE OF DAYS WITH SOME
DECELERATION AS THE TROPICAL CYCLONE NEARS A WEAKNESS IN THE RIDGE.
IN THE LATTER PART OF THE FORECAST PERIOD...MOST OF THE GUIDANCE
SHOWS A TURN TOWARD THE NORTHWEST AS KATIA APPROACHES THE SOUTHWEST
SIDE OF THE SUBTROPICAL ANTICYCLONE.  THE OFFICIAL TRACK FORECAST
FOR THIS ADVISORY PACKAGE IS AN UPDATE OF THE PREVIOUS ONE AND IS
CLOSE TO THE VARIOUS MODEL CONSENSUS TRACKS.

FORECAST POSITIONS AND MAX WINDS

INIT  31/1500Z 14.2N  40.8W   55 KT  65 MPH
 12H  01/0000Z 14.7N  43.3W   65 KT  75 MPH
 24H  01/1200Z 15.4N  46.3W   75 KT  85 MPH
 36H  02/0000Z 16.2N  48.7W   85 KT 100 MPH
 48H  02/1200Z 17.3N  51.0W   90 KT 105 MPH
 72H  03/1200Z 19.5N  54.5W   95 KT 110 MPH
 96H  04/1200Z 21.5N  57.5W  100 KT 115 MPH
120H  05/1200Z 23.5N  60.5W  105 KT 120 MPH

$$
FORECASTER PASCH



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