[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 020237
TCDAT2

TROPICAL STORM KATIA DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST THU SEP 01 2011

MICROWAVE IMAGES AROUND 2245 UTC SHOWED THE CENTER OF KATIA ON THE
EDGE OF THE DEEP CONVECTION...BUT MORE RECENT SATELLITE IMAGES SHOW
AN INCREASE OF THE THUNDERSTORM ACTIVITY AND IT APPEARS THAT THE
CENTER IS AGAIN UNDER THE CANOPY. THE OUTFLOW HAS ALSO BECOME A
LITTLE BETTER DEFINED IN THE NORTHWEST QUADRANT. DVORAK T-NUMBERS
ONLY SUPPORT 55 KNOTS BUT GIVEN THAT THE CLOUD PATTERN IS A LITTLE
BETTER ORGANIZED THAN EARLIER THIS EVENING...THE INITIAL INTENSITY
IS KEPT AT 60 KNOTS.  WATER VAPOR IMAGES STILL SHOW A SHARP
UPPER-TROUGH WITH ITS AXIS ALONG 56 DEGREES WEST LONGITUDE INDUCING
STRONG SOUTHWESTERLY SHEAR OVER KATIA. GLOBAL MODELS...MAINLY THE
GFS AND EVENTUALLY THE ECMWF INSIST ON WEAKENING THIS TROUGH AND
FORECAST A MORE FAVORABLE ENVIRONMENT FOR INTENSIFICATION IN A DAY
OR SO. THERE ARE NO SIGNS THAT THE TROUGH IS WEAKENING YET...AND
GIVEN THE CURRENT SHEAR...NO CHANGE IN STRENGTH IS INDICATED IN THE
NEXT 12 TO 18 HOURS.  KATIA SHOULD BEGIN TO RE-INTENSIFY IN ABOUT 24
TO 36 HOURS AND BECOME A MAJOR HURRICANE IN A FEW DAYS ASSUMING
THAT THE ENVIRONMENT BECOMES LESS HOSTILE AS INDICATED BY GLOBAL
MODELS.

KATIA HAS SLOWED DOWN A LITTLE BIT AND IT APPEARS TO BE MOVING
TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 14 KNOTS AROUND THE
PERIPHERY OF THE SUBTROPICAL RIDGE. A TROUGH CURRENTLY LOCATED OVER
THE WESTERN ATLANTIC IS ERODING THE WESTERN SIDE OF THE SUBTROPICAL
RIDGE AND THIS WILL INDUCE A NORTHWESTERLY MOTION DURING THE NEXT
TWO TO THREE DAYS. HOWEVER...IN THE LONG RANGE...A STRONG MID-LEVEL
TROUGH IS FORECAST TO DEVELOP OVER THE GULF OF MEXICO AS THE
ATLANTIC SUBTROPICAL RIDGE BUILDS WESTWARD. THIS PATTERN SHOULD
FORCE KATIA ON A MORE WEST-NORTHWESTWARD MOTION BY THE END OF THE
FORECAST PERIOD AS INDICATED BY THE ECMWF AND THE GFS. THIS SMALL
BEND TO THE WEST-NORTHWEST IS REFLECTED IN THE OFFICIAL FORECAST.

ON THE FORECAST TRACK...KATIA WILL CONTINUE TO MOVE OVER OPEN WATER
DURING THE NEXT FIVE DAYS.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 16.7N  50.6W   60 KT  70 MPH
 12H  02/1200Z 17.5N  52.5W   60 KT  70 MPH
 24H  03/0000Z 18.5N  54.0W   65 KT  75 MPH
 36H  03/1200Z 19.5N  55.5W   75 KT  85 MPH
 48H  04/0000Z 20.5N  57.0W   85 KT 100 MPH
 72H  05/0000Z 22.5N  60.0W   95 KT 110 MPH
 96H  06/0000Z 25.0N  63.5W  100 KT 115 MPH
120H  07/0000Z 26.5N  67.0W  105 KT 120 MPH

$$
FORECASTER AVILA



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