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TROPICAL DEPRESSION FOURTEEN DISCUSSION NUMBER 5
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT TUE OCT 15 2002
TROPICAL DEPRESSION FOURTEEN HAS CHANGED LITTLE DURING THE PAST 12
TO 18 HOURS WHILE DRIFTING/MEANDERING SLOWLY TO THE NORTHEAST. THE
LAST REPORT FROM A RECONNAISSANCE AIRCRAFT INDICATE THAT THE
HIGHEST FLIGHTL-LEVEL WINDS WERE 35 KT AND THE CENTRAL PRESSURE WAS
STILL 1004 MB...SO THE INITIAL INTENSITY IS HELD AT 30 KT. THE
UPPER-LEVEL OUTFLOW PATTERN IS STILL QUITE IMPRESSIVE...EXCEPT THAT
THE LOW-LEVEL CENTER REMAINS SHEARED AT LEAST 120 NMI WEST OF THE
UPPER-LEVEL ANTICYCLONE.
THERE IS CONSIDERABLE UNCERTAINTY IN THE INITIAL MOTION ESTIMATE...
BUT A 12 HOUR TREND YIELDS ABOUT 045/04. THE GLOBAL MODEL GUIDANCE
HAS BEEN LESS THAN STERLING THE PAST 24 HOURS...WITH ALL THE MODELS
YESTERDAY AGREEING ON THE DEPRESSION BEING EAST OF HAVANA AT THIS
TIME. THE MODELS HAVE NOT HANDLED WELL THE STRENGTH AND LOCATION OF
THE 850 AND 700 MB RIDGE LOCATED NORTH OF THE GREATER ANTILLES THAT
EXTENDS AS FAR WEST AS CENTRAL CUBA...BASED ON RECENT 12Z UPPER-AIR
DATA. DUE TO THE STRENGTH AND WESTWARD EXTENT OF THIS LOW-LEVEL
RIDGE...I HAVE SHIFTED THE FORECAST TRACK SLIGHTLY TO THE EAST AND A
LITTLE SLOWER THAN THE PREVIOUS FORECAST THROUGH 36 HOURS AND THEN
BRING IT BACK ON TRACK AFTER THAT. THERE IS A TIGHT PACKING OF THE
NHC MODEL GUIDANCE ON TAKING THE DEPRESSION QUICKLY TO THE NORTHEAST
ACROSS CENTRAL CUBA IN 12 HOURS AND ACROSS THE CENTRAL BAHAMAS IN 24
HOURS. HOWEVER...THERE HAS BEEN SIMILAR STRONG AGREEMENT FOR THE
PAST 24 HOURS...AND THE DEPRESSION IS STILL DEEP IN THE CARIBBEAN
SEA. TIMING OF THE EROSION OF THE LOW-LEVEL RIDGE IS TRICKY AT BEST.
THE STRONG SHORTWAVE TROUGH OVER THE NORTHEAST GULF OF MEXICO THAT
WAS SUPPOSED TO HAVE ALREADY PICKED UP THE TROPICAL CYCLONE IS
BEGINNING TO LIFT OUT TO THE NORTHEAST BASED ON LATEST WATER VAPOR
TRENDS AND 12Z UPPER-AIR DATA. MY BEST GUESS IS THAT THE NEXT
STRONGER UPSTREAM TROUGH OVER THE NORTHERN AND CENTRAL PLAINS WILL
HAVE TO DROP DOWN INTO THE MEAN LONGWAVE TROUGH AND LIFT OUT THE
DEPRESSION. UNFORTUNATELY...THAT MAY NOT OCCUR FOR ANOTHER 24 HOURS
WHICH WOULD LEAVE TD 14 STILL MEANDERING OVER THE NORTHWEST
CARIBBEAN FOR ANOTHER 12 TO 18 HOURS. THE OFFICIAL TRACK IS CLOSE TO
THE UKMET-GFS-NOGAPS-GFDL CONSENSUS FOR DIRECTION...BUT SIMILAR TO
THE SLOWER GFS ENSEMBLE MEAN MODEL FOR SPEED.
THE DEPRESSION COULD STILL STRENGTHEN INTO A TROPICAL STORM GIVEN
THAT IT IS OVER 29C WATER AND CONVECTIVE BANDING FEATURES HAVE BEEN
IMPROVING THIS MORNING. STRENGTHENING AFTER 36 HOURS IS EXPECTED TO
RESULT FROM BAROCLINIC ENERGY SOURCES AS THE CYCLONE COMES UNDER THE
INFLUENCE OF A STRONG NEGATIVELY-TILTED UPPER-LEVEL TROUGH. RAPID
TRANSITION INTO AN EXTRATROPICAL LOW NORTHEAST OF THE BAHAMAS SHOULD
OCCUR AS A RESULT OF THIS MID-LATITUDE INTERACTION.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 15/1500Z 17.9N 82.7W 30 KTS
12HR VT 16/0000Z 19.3N 81.3W 35 KTS
24HR VT 16/1200Z 21.7N 79.2W 40 KTS
36HR VT 17/0000Z 24.6N 76.7W 45 KTS
48HR VT 17/1200Z 29.5N 72.3W 50 KTS...EXTRATROPICAL
72HR VT 18/1200Z 40.0N 63.0W 50 KTS...EXTRATROPICAL
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