[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 231443
TCDAT3

TROPICAL STORM LORENZO DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132013
1100 AM AST WED OCT 23 2013

VISIBLE SATELLITE IMAGES SHOW A STRONGLY SHEARED TROPICAL
CYCLONE...WITH THE MAIN AREA OF DEEP CONVECTION DISPLACED WELL TO
THE SOUTHEAST OF THE LOW-LEVEL CENTER OF CIRCULATION BY STRONG
UPPER-LEVEL NORTHWESTERLY WINDS.  BASED ON A BLEND OF DVORAK T- AND
CI-NUMBERS...THE INTENSITY IS REDUCED TO 40 KT FOR THIS ADVISORY.
DYNAMICAL GUIDANCE INDICATES THAT THE SHEAR WILL RELAX BRIEFLY IN
24-36 HOURS AS AN UPPER-LEVEL ANTICYCLONE SHIFTS EASTWARD AND COMES
IN PHASE WITH LORENZO.  BY THAT TIME HOWEVER...IT IS ANTICIPATED
THAT THE TROPICAL CYCLONE WILL HAVE WEAKENED SO MUCH THAT IT WILL
BE UNABLE TO TAKE ADVANTAGE OF THESE CONDITIONS.  THE OFFICIAL
FORECAST...LIKE THE PREVIOUS ONE...CALLS FOR THE SYSTEM TO
DEGENERATE INTO A REMNANT LOW BY 48 HOURS AND TO DISSIPATE
COMPLETELY THEREAFTER.  THIS IS ALSO SHOWN BY MOST OF THE NUMERICAL
GUIDANCE.

THE FORWARD MOTION HAS SLOWED SOMEWHAT AND THE CYCLONE IS NOW MOVING
EASTWARD NEAR 5 KT.  LORENZO IS CURRENTLY MOVING ALONG THE NORTHERN
SIDE OF A LOW- TO MID-LEVEL RIDGE.  ASIDE FROM THE SLOWER
MOTION...THE TRACK FORECAST AND REASONING ARE MOSTLY THE SAME.
GLOBAL MODELS SHOW A LOW- TO MID-LEVEL RIDGE BUILDING TO THE EAST
OF LORENZO DURING THE NEXT DAY OR TWO.  THIS...ALONG WITH FLOW
AHEAD OF AN APPROACHING COLD FRONT...SHOULD CAUSE LORENZO OR ITS
REMNANT LOW TO TURN NORTHEASTWARD.  THE OFFICIAL TRACK FORECAST IS
CLOSE TO THE LATEST DYNAMICAL MODEL CONSENSUS...TVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 29.5N  49.0W   40 KT  45 MPH
 12H  24/0000Z 29.9N  48.1W   35 KT  40 MPH
 24H  24/1200Z 30.5N  47.5W   30 KT  35 MPH
 36H  25/0000Z 31.5N  46.5W   30 KT  35 MPH
 48H  25/1200Z 32.7N  44.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/1200Z...DISSIPATED

$$
FORECASTER PASCH


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