Tropical Depression NINETEEN

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TROPICAL DEPRESSION NINETEEN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192012
500 AM AST TUE OCT 23 2012
 
ENHANCED INFRARED BD-CURVE IMAGERY INDICATES THAT THE CLOUD PATTERN
OF THE DEPRESSION HAS CHANGED LITTLE THIS MORNING...WITH ISOLATED
PATCHES OF DEEP CONVECTION NEAR AND SURROUNDING THE CENTER OF
CIRCULATION.  WATER VAPOR AND MICROWAVE IMAGERY SHOW SOME DRY AIR
ASSOCIATED WITH AN UPPER-LEVEL TROUGH TO THE WEST OF THE CYCLONE
INTRUDING IN THE SOUTHWEST QUADRANT.  SUBSEQUENTLY...THE TAFB
FINAL-T NUMBER HAS DECREASED TO 30 KT WHILE THE SAB ESTIMATE
REMAINS UNCHANGED AT 35 KT...AND THE INITIAL INTENSITY IS AGAIN HELD
AT 30 KT FOR THIS ADVISORY.  SOME STRENGTHENING IS POSSIBLE DURING
THE NEXT 36-48 HR BEFORE INCREASING WESTERLY SHEAR AND COOLER SEA
SURFACE TEMPERATURES BEGIN TO NEGATIVELY AFFECT THE CYCLONE. THE FSU
CYCLONE PHASE EVOLUTION FORECAST...BASED ON THE GFS AND UKMET
MODELS...INDICATES EXTRATROPICAL TRANSITION IN ABOUT 72 HR.
AFTERWARD...THE GLOBAL MODELS...INCLUDING THE ECMWF...SHOW THE
POST-TROPICAL LOW GRADUALLY WEAKENING AND BECOMING ABSORBED BY A
LARGE BAROCLINIC LOW OVER THE NORTH ATLANTIC IN AROUND 5 DAYS.  THE
NHC FORECAST FOLLOWS SUIT AND THE INTENSITY FORECAST IS BASED ON
THE TVCA MULTI-MODEL CONSENSUS.
 
WITH SHORTWAVE INFRARED IMAGERY...IT IS DIFFICULT TO LOCATE THE
ILL-DEFINED CENTER THIS MORNING.  IN FACT...AN EARLIER METOP-A
AMSU-B MICROWAVE IMAGE SUGGESTED THAT THERE MAY BE MULTIPLE
LOW-LEVEL CENTERS.  WITH THAT...THE INITIAL POSITION IS BASED ON
A MEAN CENTER AND ADJUSTMENTS MAY BE REQUIRED LATER THIS MORNING. 
CONSEQUENTLY...THE INITIAL MOTION IS A RATHER UNCERTAIN 015/10. 
THE CYCLONE IS EMBEDDED IN SOUTHERLY MID-LEVEL FLOW PRODUCED BY A
DEEP-LAYER TROUGH MOVING OVER THE CENTRAL ATLANTIC AND A
MID-TROPOSPHERIC HIGH SITUATED WEST OF THE CAPE VERDE ISLANDS.  THE
LARGE-SCALE MODELS CONTINUE TO SHOW THE DEPRESSION MAKING A TURN
TOWARD THE EAST-NORTHEAST AND ACCELERATING AROUND THE 36-HR PERIOD
IN RESPONSE TO THE APPROACHING AFOREMENTIONED TROUGH.  THROUGH THE
REMAINING PERIOD...THE CYCLONE SHOULD CONTINUE IN A GENERAL
EAST-NORTHEASTWARD TRACK WITHIN THE MID-LATITUDE WESTERLIES.  THE
OFFICIAL TRACK FORECAST IS CLOSE TO THE TVCA CONSENSUS MODEL AND A
LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY BUT CLOSER TO THE MODEL
CLUSTER AT DAY 4.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0900Z 24.1N  51.5W   30 KT  35 MPH
 12H  23/1800Z 25.3N  50.9W   35 KT  40 MPH
 24H  24/0600Z 26.6N  49.4W   40 KT  45 MPH
 36H  24/1800Z 27.5N  47.1W   40 KT  45 MPH
 48H  25/0600Z 28.5N  44.5W   45 KT  50 MPH
 72H  26/0600Z 31.6N  38.1W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  27/0600Z 36.4N  33.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  28/0600Z...DISSIPATED
 
$$
FORECASTER ROBERTS
 
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