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TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 8
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT MON SEP 10 2001
AFTERNOON VISIBLE IMAGES OF TROPICAL DEPRESSION DO LITTLE TO DISPEL
THE PROBLEM OF TWO DISTINCT LOW-LEVEL CENTERS. CONVECTION
ASSOCIATED WITH THE SOUTHERN CIRCULATION HAS DISSIPATED WHILE
CONVECTION WITH THE NORTHERN VORTEX HAS PERSISTED THROUGH THE DAY.
A DRIFTING BUOY REPORTED SOUTHWEST WINDS NEAR 14.9N 46.4W...WHICH
WOULD SUPPORT A CLOSED CIRCULATION...HOWEVER IT WAS NOT CLEAR
WHETHER THOSE WINDS WERE ASSOCIATED WITH OUTFLOW FROM THE
DISSIPATING CONVECTION..OR THE SYNOPTIC-SCALE SYSTEM.
CLASSIFICATIONS FROM TAFB AND SAB ARE BOTH TRACKING THE NORTHERN
VORTEX...AND IT IS BECOMING MORE APPARENT THAT THIS IS THE MORE
DOMINANT CIRCULATION IN THIS COMPLEX SYSTEM. CURRENT INTENSITY
ESTIMATES ARE 2.5 AND 2.0 FROM TAFB AND SAB RESPECTIVELY. INITIAL
INTENSITY REMAINS AT 30 KT FOR THIS ADVISORY BASED ON THE OVERALL
APPEARANCE OF A BROAD AND SOMEWHAT DISORGANIZED CIRCULATION CENTER.
A NARROW MID- TO UPPER-LEVEL TROUGH EXTENDING SOUTHWEST FROM A
LARGER TROUGH OVER THE NORTHEAST ATLANTIC IS EXPECTED TO CREATE A
WEAKNESS IN THE SUBTROPICAL RIDGE NOT FAR AHEAD OF THE DEPRESSION.
NUMERICAL GUIDANCE CONTINUES TO LIFT THE SYSTEM NORTHWEST THROUGH
THE FIRST 48 HOURS...THEN NORTHWARD THROUGH 72 HOURS. THE CURRENT
NHC FORECAST IS SIMILAR TO THE PREVIOUS PREVIOUS FORECAST TRACK.
HOWEVER THERE HAS BEEN A SLIGHT OVERALL SHIFT TO THE RIGHT DUE TO A
SLIGHT RELOCATION OF THE CENTER TO THE NORTH. THIS IS A BIT LEFT OF
THE CENTER OF THE OBJECTIVE GUIDANCE ENVELOPE.
FORECASTER PASCH/HOLWEG
FORECAST POSITIONS AND MAX WINDS
INITIAL 10/2100Z 17.2N 46.3W 30 KTS
12HR VT 11/0600Z 18.0N 48.0W 30 KTS
24HR VT 11/1800Z 19.0N 49.5W 35 KTS
36HR VT 12/0600Z 20.0N 50.5W 45 KTS
48HR VT 12/1800Z 21.0N 51.5W 55 KTS
72HR VT 13/1800Z 24.0N 52.0W 60 KTS
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