000 WTNT42 KNHC 312039 TCDAT2 TROPICAL STORM KATIA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 500 PM AST WED AUG 31 2011 KATIA IS NEAR THE THRESHOLD OF HURRICANE STATUS. THE SYSTEM CONTINUES TO EXHIBIT PROMINENT CURVED CONVECTIVE BANDS AND DEEP CONVECTION IS BECOMING STRONGER OVER THE CENTER. THE STORM ALSO HAS A FAIRLY SYMMETRIC AND WELL-ESTABLISHED UPPER-LEVEL OUTFLOW PATTERN. DVORAK INTENSITY ESTIMATES FROM BOTH AGENCIES REMAIN AT 55 KT...BUT AMSU INTENSITY ESTIMATES FROM THE UNIVERSITY OF WISCONSIN CIMSS ARE A LITTLE HIGHER. THE INTENSITY IS SET AT 60 KT FOR THIS ADVISORY. WEAK VERTICAL SHEAR AND MODESTLY WARM WATERS ARE LIKELY TO PREVAIL OVER THE NEXT FEW DAYS...SO CONTINUED INTENSIFICATION IS FORECAST. A LARGE UPPER-LEVEL LOW TO THE NORTHWEST OF KATIA COULD CAUSE AN INCREASE IN SHEAR...AND INHIBIT INTENSIFICATION...LATE IN THE FORECAST PERIOD. HOWEVER SOME OF THE GLOBAL MODELS...SUCH AS THE GFS...SUGGEST THAT THE OUTFLOW ANTICYCLONE OF KATIA WILL DOMINATE THE UPPER-LEVEL WIND PATTERN AND DISPLACE THE SHEARING FLOW ASSOCIATED WITH THE LOW. IF THAT OCCURS...KATIA WOULD LIKELY BECOME A MAJOR HURRICANE BY DAY 4 OR 5. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND SLIGHTLY HIGHER THAN THE STATISTICAL-DYNAMICAL GUIDANCE. THE STORM CONTINUES TO MOVE WEST-NORTHWESTWARD ON THE SOUTH SIDE OF A SUBTROPICAL ANTICYCLONE. THE TRACK FORECAST AND REASONING ARE ESSENTIALLY UNCHANGED. AS KATIA NEARS THE SOUTHWEST SIDE OF THE ANTICYCLONE...A GRADUAL TURN TOWARD THE NORTHWEST WITH DECREASING FORWARD SPEED IS LIKELY. THE CURRENT OFFICIAL TRACK FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND ABOUT IN THE MIDDLE OF THE GUIDANCE ENVELOPE. IT IS ALSO A LITTLE TO THE WEST OF THE GFS AND ECMWF SOLUTIONS. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 14.6N 42.6W 60 KT 70 MPH 12H 01/0600Z 15.1N 44.9W 65 KT 75 MPH 24H 01/1800Z 15.8N 47.7W 75 KT 85 MPH 36H 02/0600Z 16.6N 50.0W 85 KT 100 MPH 48H 02/1800Z 17.7N 52.0W 90 KT 105 MPH 72H 03/1800Z 20.0N 55.5W 95 KT 110 MPH 96H 04/1800Z 22.0N 58.5W 100 KT 115 MPH 120H 05/1800Z 23.5N 61.0W 105 KT 120 MPH $$ FORECASTER PASCH