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Tropical Depression Twelve Discussion Number   2
NWS National Hurricane Center Miami FL       AL122023
800 PM CVT Fri Sep 01 2023
 
A 1458 UTC AMSR-2 microwave pass showed that the depression has a
well-defined circulation, however the associated deep convection
was rather disjointed.  Dvorak CI numbers classifications are still
T2.5 from TAFB, but the final-T number dropped to 2.0 from SAB, so
the system is still being classified as a 30-kt depression at this
time.  Some more defined convective bands are now developing within
the circulation, so the system may be on its way to becoming a
tropical storm.  ASCAT data should provide a better handle on the
maximum winds of the system this evening.
 
The initial motion is toward the north-northwest (345 degrees) at 10
kt, with the depression situated between a mid-level ridge over
western Africa and a mid- to upper-level low over the
eastern/central Atlantic.  Another ridge near the Azores is expected
to force the depression to turn northwest and then west-northwest
around the mid-level low during the next few days.  The NHC track
forecast is a little east of the previous forecast near the
multi-model consensus aids, but this is more a function of an
adjustment of the initial position.  Once the system becomes a
remnant low, the low-level flow should turn it toward the northwest
and north on days 3 and 4.
 
The depression has a small window of relatively low shear, warm
waters, and a sufficiently moist atmosphere to strengthen to a
tropical storm tonight or on Saturday, which is shown in the
official forecast.  However, the system will be moving into a much
drier atmosphere with strengthening southerly shear, which should
cause weakening to begin in about 36 hours.  Organized deep
convection could also dissipate in a couple of days, and the
cyclone is forecast to become a remnant low by 48 hours.  Global
model fields suggest the remnant low could last a little bit longer
than shown in the previous forecast, and dissipation is now shown a
day later on day 5.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 20.8N  28.7W   30 KT  35 MPH
 12H  02/0600Z 22.2N  29.5W   35 KT  40 MPH
 24H  02/1800Z 24.0N  30.8W   35 KT  40 MPH
 36H  03/0600Z 25.4N  32.3W   30 KT  35 MPH
 48H  03/1800Z 26.3N  33.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  04/0600Z 26.9N  34.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  04/1800Z 27.7N  35.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  05/1800Z 29.4N  35.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  06/1800Z...DISSIPATED
 
$$
Forecaster Berg
 
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