ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM 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 NNNN
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