HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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TROPICAL DEPRESSION TEN SPECIAL DISCUSSION NUMBER   1
NATIONAL WEATHER SERVICE MIAMI FL
6 AM EDT SUN SEP 19 1999
 
SATELLITE IMAGERY INDICATES INCREASED CONVECTION NEAR AND EAST OF
THE CENTER OF THE BROAD LOW PRESSURE AREA IN THE CENTRAL GULF OF
MEXICO. OBSERVATIONS FROM BUOYS 42001 AND 42003 SUGGEST A MINIMUM
CENTRAL PRESSURE AROUND 1005 MB...WITH 42003 REPORTING 30 KT WINDS
AT 0900Z. THUS...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION
TEN.

THE INITIAL MOTION IS 345/04. A STRONG DEEP LAYER TROUGH IS FORECAST
TO AMPLIFY OVER THE EASTERN U.S. DURING THE NEXT 72 HOURS. THIS...IN
THEORY...SHOULD TURN THE CYCLONE NORTHEAST OR EVEN EAST-NORTHEAST
ACROSS THE SOUTHEASTERN U.S. OR FLORIDA. HOWEVER...MODEL GUIDANCE
HAS A GREAT VARIETY OF SOLUTIONS. THE UKMET TAKES THE CYCLONE ON THE
TRACK SUGGESTED BY THE SYNOPTIC PATTERN. ON THE OTHER HAND...THE AVN
LETS THE DEPRESSION LINGER IN THE GULF UNTIL THE ONCOMING COLD FRONT
ASSOCIATED WITH THE TROUGH CATCHES IT. THE AVN ALSO DEVELOPS A
SECONDARY LOW OFF THE SOUTHEAST U.S. COAST. THE OFFICIAL FORECAST
GOES WITH THE SYNOPTICALLY SUGGESTED TRACK AND IS A COMPROMISE
BETWEEN A NORTHERLY UKMET AND A SOUTHERLY LBAR AND NHC98E. 

DEEP CONVECTION IS STILL POORLY ORGANIZED...WITH SATELLITE INTENSITY
ESTIMATES OF ONLY 25 KT. THE LARGE SCALE MODELS DEVELOP AN UPPER
LEVEL ANTICYCLONE OVER THE EASTERN GULF. HOWEVER...WATER VAPOR
IMAGERY SUGGESTS A WEAK TROUGH OR SHEAR AXIS IS EMBEDDED IN THE
ANTICYCLONE JUST WEST OF THE DEPRESSION...WHICH RESTRICTS OUTFLOW TO
THE WEST. THESE POINTS SUGGEST INTENSIFICATION SHOULD BE SLOW. LATER
INTENSIFICATION WILL DEPEND ON HOW THE DEPRESSION INTERACTS WITH THE
DEVELOPING TROUGH. BY 72 HOURS THE CYCLONE COULD SHEAR OFF...START
BECOMING EXTRATROPICAL...OR EVOLVE INTO A HYBRID OR SUBTROPICAL
CYCLONE. THE INTENSITY FORECAST WILL BRING THE SYSTEM TO 50 KT IN 48
HOURS AND KEEP THAT INTENSITY AT 72 HOURS. THIS IS A COMPROMISE
BETWEEN POSSIBLE WEAKENING DUE TO SHEAR AND POSSIBLE DEEPENING DUE
TO BAROCLINIC INTERACTION.

WHILE NO WATCHES OR WARNINGS WILL BE ISSUED WITH THIS PACKAGE...THEY
MAY BE REQUIRED LATER TODAY. RESIDENTS OF THE NORTHERN AND EASTERN
GULF COAST SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.
 
BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/1000Z 24.9N  88.0W    30 KTS
12HR VT     19/1800Z 25.4N  88.1W    35 KTS
24HR VT     20/0600Z 26.2N  88.2W    40 KTS
36HR VT     20/1800Z 27.5N  87.4W    45 KTS
48HR VT     21/0600Z 28.5N  85.5W    50 KTS
72HR VT     22/0600Z 31.0N  79.0W    50 KTS
 
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