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#631021 (Received by flhurricane at: 10:53 PM 10.Sep.2013) TCDAT4 TROPICAL STORM HUMBERTO DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013 1100 PM AST TUE SEP 10 2013 AN EYE HAS BEEN SHOWING UP INTERMITTENTLY THIS EVENING IN HUMBERTO...BUT HAS NOT PERSISTED. MOREOVER...THE DEEP CONVECTION HAS BEEN SOMEWHAT ASYMMETRIC AND IS NOT MAINTAINING A CENTRAL DENSE OVERCAST CONTINUOUSLY. DVORAK CURRENT INTENSITY ESTIMATES FROM TAFB AND SAB HAVE REMAINED THE SAME OVER THE LAST SIX HOURS...AVERAGING AT 60 KT...WHILE ADT AND CIMSS AMSU SUGGEST A SUBSTANTIALLY WEAKER CYCLONE. IN DEFERENCE TO THE SUBJECTIVE DVORAK ANALYSES AND THE INTERMITTENT EYE...THE INITIAL INTENSITY REMAINS 60 KT. WHILE NO NEW ASCAT OBSERVATIONS WERE AVAILABLE...A 2240Z CIRA AMSU SIZE ANALYSIS SUGGESTED A SLIGHTLY LARGER RADIUS OF TROPICAL STORM FORCE WINDS...WHICH HAS BEEN SO ADJUSTED. HUMBERTO SHOULD STILL REACH HURRICANE INTENSITY...AS IT HAS ABOUT 24-36 HOURS TO GO WHILE TRAVERSING LUKEWARM WATER AND AN ENVIRONMENT OF LOW VERTICAL WIND SHEAR. BUT IN ABOUT 36-48 HOURS...THE VERTICAL SHEAR SHOULD INCREASE SUBSTANTIALLY DUE TO HUMBERTO APPROACHING CLOSER TO A LARGE UPPER-LEVEL TROUGH...WHILE AT THE SAME TIME THE SSTS SHOULD DROP TO A COOLISH 25-26C. GRADUAL...IF NOT RAPID...WEAKENING SHOULD OCCUR BETWEEN DAYS 2 AND 4. THE INTENSITY GUIDANCE IS RATHER TIGHTLY CLUSTERED AND THE NHC PREDICTION MIRRORS THIS AND IS JUST SLIGHTLY LOWER THAN THE PREVIOUS ADVISORY. HUMBERTO IS MOVING AT ABOUT 6 KT TOWARD 315 DEGREES...PRIMARILY DUE TO THE INFLUENCE OF A MID-LAYER RIDGE TO ITS NORTHEAST. WITH THE RIDGE WEAKENING...THE CYCLONE SHOULD TURN NORTHWARD IN ABOUT A DAY AND CONTINUE THIS MOTION FOR ANOTHER DAY OR SO. AROUND DAY 3...HUMBERTO SHOULD TURN AGAIN...THIS TIME TOWARD THE WEST...AS A STRONGER DEEP-LAYER RIDGE BUILDS IN NEAR THE AZORES. THE TRACK FORECAST IS BASED UPON A BLEND OF THE GFS...ECMWF...AND FIM GLOBAL MODELS...AND IS NEARLY IDENTICAL TO THE PREVIOUS ADVISORY THROUGH 48 HOURS AND THEN SLIGHTLY SOUTH THEREAFTER. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 15.4N 28.4W 60 KT 70 MPH 12H 11/1200Z 16.4N 28.9W 65 KT 75 MPH 24H 12/0000Z 18.3N 29.1W 70 KT 80 MPH 36H 12/1200Z 20.2N 29.4W 75 KT 85 MPH 48H 13/0000Z 21.7N 29.9W 70 KT 80 MPH 72H 14/0000Z 23.5N 32.5W 60 KT 70 MPH 96H 15/0000Z 24.0N 37.5W 45 KT 50 MPH 120H 16/0000Z 24.5N 43.0W 40 KT 45 MPH $$ FORECASTER LANDSEA |