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Tropical Storm LORENZO

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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
 
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