| Track: http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/203649.shtml?5day?large#contents Floater: http://www.ssd.noaa.gov/PS/TROP/floaters/13L/13L_floater.html TROPICAL STORM LORENZO DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132013 500 PM AST MON OCT 21 2013 THE SATELLITE PRESENTATION OF THE CYCLONE HAS BECOME BETTER ORGANIZED SINCE THIS MORNING. A CURVED BAND CONSISTING OF COLD- TOPPED CONVECTION HAS LENGTHENED AND BECOME BETTER DEFINED...EVEN THOUGH THE LOW-LEVEL CENTER OF THE CYCLONE IS EXPOSED AT THE WESTERN TIP. IN ADDITION...A 1254 UTC ASCAT-A PASS HAD A COUPLE OF 34-KT WIND VECTORS EAST-SOUTHEAST OF THE CENTER. BASED ON THE EARLIER ASCAT PASS...THE DEPRESSION IS UPGRADED TO A TROPICAL STORM WITH AN INITIAL INTENSITY OF 35 KT. THE ASCAT PASSES AND FIXES FROM VISIBLE SATELLITE IMAGERY TODAY HAVE ALLOWED FOR A BETTER ASSESSMENT OF THE INITIAL MOTION WHICH IS ESTIMATED TO BE 030/06...TO THE LEFT OF THE PREVIOUS ESTIMATE. THE FORECAST PHILOSOPHY REMAINS THE SAME. LORENZO SHOULD BE STEERED NORTH-NORTHEASTWARD AND THEN NORTHEASTWARD DURING THE NEXT DAY OR SO AROUND THE NORTHWEST SIDE OF A MID-LEVEL RIDGE. AFTER THAT TIME... THE CYCLONE SHOULD TURN EAST-NORTHEASTWARD ALONG THE SOUTHERN EDGE OF NEARLY ZONAL FLOW NEAR 30N. THE NHC TRACK FORECAST IS ADJUSTED SIGNIFICANTLY TO THE LEFT OF THE PREVIOUS ONE DUE TO A MORE NORTH-NORTHEASTERLY INITIAL MOTION...AND IS JUST AHEAD OF THE MULTI-MODEL CONSENSUS TO BETTER MATCH THE FASTER GFS/ECMWF SOLUTIONS. SOME INTENSIFICATION IS EXPECTED DURING THE NEXT DAY OR SO WHILE THE CYCLONE IS OVER WARM WATERS AND IN THE DIFFLUENT FLOW EAST OF AN UPPER-LEVEL CYCLONIC SHEAR AXIS. BY 36 HOURS...SHIPS OUTPUT SHOWS A CONSIDERABLE INCREASE IN WESTERLY VERTICAL WIND SHEAR THAT SHOULD RESULT IN A DECOUPLING OF THE CYCLONE IN 2 TO 3 DAYS. THE GUIDANCE SHOWS THE REMNANT CIRCULATION IS LIKELY TO DISSIPATE AHEAD OF AN APPROACHING BAROCLINIC ZONE IN 3 TO 4 DAYS. THE NHC INTENSITY FORECAST IS RAISED SLIGHTLY OVER THE PREVIOUS ONE...AND IS GENERALLY NEAR THE MULTI-MODEL CONSENSUS BUT A BIT LOWER THAN THE SHIPS/LGEM OUTPUT. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 28.9N 54.9W 35 KT 40 MPH 12H 22/0600Z 29.5N 53.9W 40 KT 45 MPH 24H 22/1800Z 29.9N 52.5W 45 KT 50 MPH 36H 23/0600Z 30.3N 51.1W 40 KT 45 MPH 48H 23/1800Z 30.9N 49.8W 35 KT 40 MPH 72H 24/1800Z 33.0N 46.5W 30 KT 35 MPH 96H 25/1800Z...DISSIPATED $$ FORECASTER KIMBERLAIN |