000
WTNT44 KNHC 231432
TCDAT4
 
TROPICAL DEPRESSION NINETEEN DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192012
1100 AM AST TUE OCT 23 2012
 
THE STRUCTURE OF THE DEPRESSION CONSISTS OF A SMALL BUT PERSISTENT
CLUSTER OF DEEP CONVECTION REGENERATING NEAR THE CENTER OF
CIRCULATION AND AN OUTER BAND FARTHER TO THE NORTH AND NORTHEAST.
UW-CIMSS AMSU AND ADT INTENSITY ESTIMATES ARE SUGGESTING THAT THE
DEPRESSION COULD HAVE REACHED TROPICAL STORM STRENGTH...BUT
SUBJECTIVE T-NUMBERS FROM TAFB AND SAB REMAIN T2.0.  THEREFORE...
THE SYSTEM IS BEING HELD AS A 30-KT DEPRESSION UNTIL WE GET MORE
CONSENSUS AMONG THE VARIOUS ESTIMATES.
 
WHILE THE DEPRESSION IS CURRENTLY IN A LIGHT-SHEAR ENVIRONMENT...THE 
DEEP-LAYER SOUTHWESTERLY SHEAR IS EXPECTED TO INCREASE LATER TODAY. 
THE CYCLONE SHOULD REACH WATERS COLDER THAN 26C IN ABOUT 36 TO 48
HOURS...AND THE SHIPS DIAGNOSTICS INDICATE THAT THE VERTICAL SHEAR
WILL INCREASE TO OVER 50 KT IN 2 TO 3 DAYS.  THE DEPRESSION
THEREFORE ONLY HAS A SHORT PERIOD OF TIME IN WHICH CONDITIONS ARE
MOST FAVORABLE FOR INTENSIFICATION...AND THE NHC FORECAST SHOWS THE
SYSTEM REACHING A PEAK INTENSITY OF 40 KT IN ABOUT 24 HOURS.  THE
GLOBAL MODELS INDICATE THAT THE CYCLONE SHOULD BECOME A FRONTAL LOW
BY 72 HOURS WITH NO SUBSEQUENT INFUSION OF BAROCLINIC ENERGY TO
SUPPORT A STRONG EXTRATROPICAL CYCLONE.  THE OFFICIAL FORECAST IS
THEREFORE A LITTLE LOWER THAN THE SHIPS AND LGEM MODELS ON DAYS 3
AND 4.  THERE IS DISAGREEMENT AMONG THE MODELS AS TO WHEN THE LOW
WILL DISSIPATE...WITH THE ECMWF MODEL SHOWING DISSIPATION IN 4 DAYS
WHILE THE UKMET MAINTAINS A LOW BEYOND THE FORECAST PERIOD.  THE
NHC FORECAST SHOWS DISSIPATION IN 5 DAYS...WHICH IS THE SAME
SOLUTION SHOWN BY THE GFS.

THE DEPRESSION HAS BEEN MOVING NORTH-NORTHEASTWARD A LITTLE FASTER
DURING THE PAST FEW HOURS...AND THE INITIAL MOTION ESTIMATE IS
015/13 KT.  THE FORWARD SPEED SHOULD SLOW DOWN DURING THE NEXT 24
HOURS AS THE DEPRESSION TRANSITIONS FROM A POSITION TO THE EAST OF A
MID- TO UPPER-LEVEL CUTOFF LOW INTO THE FLOW ASSOCIATED WITH THE
MID-LATITUDE WESTERLIES.  AN EAST-NORTHEASTWARD ACCELERATION SHOULD
THEN OCCUR AFTER 24 HOURS UNTIL DISSIPATION.  THE TRACK GUIDANCE
REMAINS TIGHTLY CLUSTERED...AND THE UPDATED NHC FORECAST IS JUST A
LITTLE SOUTH OF THE PREVIOUS ONE DUE TO A GENERAL SHIFT IN THE
GUIDANCE ENVELOPE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 25.7N  51.0W   30 KT  35 MPH
 12H  24/0000Z 26.7N  50.2W   35 KT  40 MPH
 24H  24/1200Z 27.8N  48.2W   40 KT  45 MPH
 36H  25/0000Z 28.5N  45.9W   40 KT  45 MPH
 48H  25/1200Z 29.5N  43.5W   40 KT  45 MPH
 72H  26/1200Z 32.5N  37.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  27/1200Z 38.0N  33.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  28/1200Z...DISSIPATED
 
$$
FORECASTER BERG