[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 230239
TCDAT3

TROPICAL STORM LORENZO DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132013
1100 PM AST TUE OCT 22 2013

SHEAR ANALYSES FROM THE UNIVERSITY OF WISCONSIN INDICATE THAT
DEEP-LAYER SHEAR NEAR LORENZO HAS TURNED OUT OF THE NORTHWEST AND
INCREASED TO NEARLY 25 KT.  AS A CONSEQUENCE...MOST OF THE DEEP
CONVECTION HAS BEEN PUSHED TO THE SOUTHEAST OF THE LOW-LEVEL
CENTER.  THERE HAVE BEEN NO ASCAT PASSES OVER LORENZO SINCE THIS
TIME YESTERDAY...SO THE INITIAL INTENSITY IS KEPT AT 45 KT BASED ON
ESTIMATES FROM INFRARED SATELLITE IMAGERY.  VERTICAL SHEAR IS
EXPECTED TO INCREASE EVEN FURTHER TO AROUND 40 KT OUT OF THE NORTH
WITHIN 24 HOURS...AND WEAKENING IS THEREFORE FORECAST TO BEGIN VERY
SOON.  THE COMBINED INFLUENCE OF VERY STRONG SHEAR AND COOLER
WATERS SHOULD CAUSE LORENZO TO DEGENERATE TO A REMNANT LOW IN 48
HOURS.  THE UPDATED NHC INTENSITY FORECAST IS CLOSE TO THE
INTENSITY CONSENSUS AND UNCHANGED FROM THE PREVIOUS FORECAST...AND
IT STILL SHOWS DISSIPATION IN 3 DAYS.

LORENZO IS LOCATED JUST TO THE NORTH OF A MID-LEVEL RIDGE AND JUST
TO THE SOUTH OF FAST MID-LATITUDE WESTERLIES...WHICH ARE STEERING
THE CYCLONE EASTWARD AT 085/8 KT.  WEAKER LOW-LEVEL FLOW SHOULD
EXERT A GREATER INFLUENCE ON STEERING AS THE CYCLONE BECOMES MORE
SHALLOW...AND LORENZO IS EXPECTED TO TURN SLOWLY NORTHEASTWARD OVER
THE NEXT 36 HOURS AHEAD OF AN APPROACHING COLD FRONT.  THERE ARE
SOME SPEED DIFFERENCES AMONG THE TRACK GUIDANCE...WITH THE GFS AND
ECMWF MODELS SHOWING A FASTER MOTION COMPARED TO THE GFDL AND HWRF
MODELS.  THE OFFICIAL TRACK FORECAST HEDGES TOWARD THE GLOBAL MODEL
SCENARIOS AND IS THEREFORE A LITTLE FASTER THAN THE MULTI-MODEL
CONSENSUS TVCA...ESPECIALLY AT 36 AND 48 HOURS.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0300Z 29.6N  50.0W   45 KT  50 MPH
 12H  23/1200Z 29.8N  49.2W   40 KT  45 MPH
 24H  24/0000Z 30.3N  48.4W   35 KT  40 MPH
 36H  24/1200Z 31.4N  47.3W   30 KT  35 MPH
 48H  25/0000Z 32.6N  45.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/0000Z...DISSIPATED

$$
FORECASTER BERG


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