000 WTNT43 KNHC 230902 TCDAT3 TROPICAL STORM SANDY DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 500 AM EDT TUE OCT 23 2012 BANDS OF VERY DEEP CONVECTION HAVE DEVELOPED OVER THE EASTERN PORTION OF THE CIRCULATION OVERNIGHT. HOWEVER...THERE APPEARS TO BE VERY LITTLE OVERALL CHANGE IN THE INNER-CORE STRUCTURE DURING THE PAST 12-18 HOURS...AS AN EARLIER ASCAT PASS INDICATED THAT SANDY STILL HAS A LARGE AREA OF LIGHT WINDS NEAR THE CENTER. SUBJECTIVE DVORAK T-NUMBERS ARE T2.5...AND THE INITIAL WIND SPEED IS MAINTAINED AT 40 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN ROUTE TO THE CYCLONE AND SHOULD PROVIDE A BETTER ASSESSMENT OF THE INTENSITY OF THE STORM. SANDY APPEARS TO BE MOVING SLOWLY NORTHWARD. THE TRACK GUIDANCE IS IN VERY GOOD AGREEMENT ON A FASTER NORTH TO NORTH-NORTHEASTWARD MOTION BEGINNING TODAY AS A MID-LEVEL RIDGE TO THE NORTH OF SANDY WEAKENS. THE CENTER OF SANDY SHOULD MOVE NEAR OR OVER JAMAICA ON WEDNESDAY AND APPROACH EASTERN CUBA BY WEDNESDAY NIGHT. THE MODEL GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH 96 HOURS WITH A TRACK ACROSS THE CENTRAL BAHAMAS. BY DAY 5...HOWEVER...THERE IS SIGNIFICANT SPREAD IN THE GUIDANCE...WITH THE ECMWF ALONG THE WESTERN EDGE OF THE GUIDANCE ENVELOPE AND THE HWRF ALONG THE EASTERN SIDE. THE GFS IS CLOSER TO THE MIDDLE OF THE GUIDANCE ENVELOPE AND THE NHC FORECAST BASED ON THE MULTI-MODEL CONSENSUS AND THE FLORIDA STATE ENSEMBLE AT DAYS 4 AND 5. ENVIRONMENTAL CONDITIONS CONSISTING OF LOW SHEAR...WARM WATERS... AND A MOIST ATMOSPHERE...FAVOR STRENGTHENING DURING THE NEXT COUPLE OF DAYS. IN FACT...ALL OF THE INTENSITY MODELS BRING SANDY TO HURRICANE STRENGTH WITHIN 36 TO 48 HOURS AND SO DOES THE NHC FORECAST. AFTER SANDY CROSSES EASTERN CUBA...THE VERTICAL SHEAR IS FORECAST TO INCREASE SIGNIFICANTLY...HOWEVER THE GLOBAL MODELS DEPICT A DEEPENING CYCLONE...POSSIBLY DUE TO SOME BAROCLINIC FORCING. THE NHC FORECAST STILL INDICATES THE SYSTEM BECOMING SUBTROPICAL LATE IN THE PERIOD...ALTHOUGH THERE ARE SOME INDICATIONS IN THE GLOBAL MODELS THAT SANDY COULD BE TRANSITIONING TO AN EXTRATROPICAL CYCLONE AROUND THAT TIME. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 13.3N 78.6W 40 KT 45 MPH 12H 23/1800Z 14.1N 78.2W 50 KT 60 MPH 24H 24/0600Z 15.6N 77.8W 60 KT 70 MPH 36H 24/1800Z 17.6N 77.4W 70 KT 80 MPH 48H 25/0600Z 19.6N 77.0W 70 KT 80 MPH 72H 26/0600Z 24.0N 76.0W 60 KT 70 MPH 96H 27/0600Z 26.8N 74.8W 60 KT 70 MPH 120H 28/0600Z 30.0N 71.5W 60 KT 70 MPH...SUBTROPICAL $$ FORECASTER BROWN