ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GABRIELLE DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 500 AM AST THU SEP 05 2013 ALTHOUGH THE AREA OF DEEP CONVECTION HAS EXPANDED SIGNIFICANTLY DURING THE PAST SEVERAL HOURS AND THE OUTFLOW IS EXCELLENT... SURROUNDING SURFACE OBSERVATIONS DO NOT SUGGEST THAT THERE HAS BEEN ANY IMPROVEMENT OF THE CIRCULATION. IN ADDITION...MICROWAVE OR DOPPLER RADAR DATA DO NOT SHOW ANY DEVELOPMENT OF AN INNER CORE...ALTHOUGH RADAR IMAGES SHOW A WELL-DEFINED MID-LEVEL CENTER TO THE EAST OF THE SURFACE LOCATION. I WOULD NOT BE SURPRISED IF THERE IS A REFORMATION OF THE SURFACE CENTER. A RECONNAISSANCE PLANE LATER THIS MORNING WILL HELP US TO DETERMINE IF THIS IS THE CASE. SUBJECTIVE ESTIMATES FROM TAFB AND SAB AS WELL AS OBJECTIVE ESTIMATES FROM THE UNIVERSITY OF WISCONSIN...CIMSS...ARE 2.5 ON THE DVORAK SCALE. ON THIS BASIS...THE INITIAL INTENSITY IS KEPT AT 35 KNOTS...AND THESE WINDS ARE PROBABLY CONFINED TO A VERY SMALL AREA NEAR THE CENTER. THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. MOST OF THE GLOBAL MODELS KEEP A WEAK CYCLONE FOR A FEW DAYS WITH THE EXCEPTION OF THE ECMWF WHICH DISSIPATES GABRIELLE JUST NORTH OF HISPANIOLA IN A COUPLE OF DAYS. GIVEN THE STRONG WESTERLY SHEAR WHICH IS FORECAST TO BECOME ESTABLISHED ALONG THE FORECAST PATH OF GABRIELLE...THE DISSIPATION OPTION OF THE ECMWF IS NOT OUT OF THE QUESTION. AT THIS TIME...THE NHC FORECAST FOLLOWS THE MODEL CONSENSUS SHOWING SOME SLIGHT STRENGTHENING GIVING CREDIT TO THE OTHER MODELS. ALTHOUGH THE SURFACE CENTER IS DIFFICULT TO FIND ON IR IMAGES...IT APPEARS TO BE ON THE WESTERN EDGE OF THE DEEP CONVECTION. THE BEST ESTIMATE OF THE INITIAL MOTION IS TOWARD THE NORTHWEST OR 320 DEGREES AT 7 KNOTS. GABRIELLE IS EMBEDDED WITHIN A WEAK STEERING FLOW SOUTH OF A NARROW RIDGE OF HIGH PRESSURE OVER THE WESTERN ATLANTIC. IN A DAY OR TWO...A MID-LEVEL TROUGH IS FORECAST TO MOVE FROM THE UNITED STATES EASTWARD ACROSS THE ATLANTIC...CAUSING GABRIELLE TO RECURVE AND MOVE TOWARD THE OPEN ATLANTIC. THE OFFICIAL FORECAST IS VERY CLOSE TO THE MULTI-MODEL CONSENSUS AND IS NOT TOO DIFFERENT FROM THE PREVIOUS ONE. REGARDLESS OF THE EXACT TRACK OF THE CENTER OF GABRIELLE DURING THE NEXT 24 HOURS...THE MAIN THREAT WILL BE HEAVY RAINFALL OVER PORTIONS OF PUERTO RICO AND THE EASTERN PORTION OF THE DOMINICAN REPUBLIC. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 17.5N 66.9W 35 KT 40 MPH 12H 05/1800Z 18.5N 67.7W 35 KT 40 MPH 24H 06/0600Z 19.7N 68.5W 40 KT 45 MPH 36H 06/1800Z 20.9N 69.1W 45 KT 50 MPH 48H 07/0600Z 21.8N 69.5W 50 KT 60 MPH 72H 08/0600Z 24.0N 69.0W 50 KT 60 MPH 96H 09/0600Z 27.0N 66.0W 50 KT 60 MPH 120H 10/0600Z 31.5N 62.5W 50 KT 60 MPH $$ FORECASTER AVILA NNNN