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Tropical Depression Fifteen Discussion Number   4
NWS National Hurricane Center Miami FL       AL152019
1100 AM AST Tue Oct 15 2019

The depression doesn't looking very healthy compared to 24 hours ago
when tightly curved convective bands wrapped around the center. Over
the past 12 hours, the convection has devolved into an elongated
north-to-south band of stratiform deep-layer cloudiness with
embedded clusters of moderate to deep convection. The western
semicircle of the broad circulation has degraded with at least two
small low-level circulations revolving southward around the mean
center. A 1045Z partial ASCAT-A pass indicated that the low-level
center was located west of 21W longitude, so the initial position
was adjusted farther west. Intensity estimates range from T1.5/25 kt
from TAFB and the partial ASCAT pass, to 33 kt and 37 kt from
UW-CIMSS ADT and SATCON, respectively. For now, the intensity will
be held at 30 kt, which is an average of these estimates.

The initial motion estimate remains northwestward, or 320/08 kt, but
this motion is of low confidence given the broad nature of the
cyclone.  Surprisingly, the models remain in quite good agreement
that the depression will move generally northwestward during the
next couple of days and pass over or just east of the northeastern
Cabo Verde Islands. A turn to the west-northwest is forecast by
72 hours and beyond due to the weak and shallow system being steered
by the low-level easterly trade wind flow. The new NHC track
forecast has been nudged a little to the left or west of the
previous advisory track, mainly due to the more westward initial
position, and lies close to the tightly packed consensus models.

The environmental conditions are expected to remain somewhat
conducive for slight strengthening during the next 12-18 hours.
Although no longer explicitly forecast, it is still possible that
the depression could briefly become a tropical storm later tonight
if a burst of deep convection can develop and tighten up the
inner-core wind field. By late Wednesday, however, the combination
of a sharp increase in southwesterly vertical wind shear, drier
mid-level air, and SSTs less than 26C should induce steady to rapid
weakening, resulting in the cyclone degenerating into a remnant low
by 36 hours and dissipating in 72-96 hours.

Regardless of whether or not the depression becomes a tropical storm
before passing near the Cabo Verde Islands, the primary threat from
this system is the potential for locally heavy rainfall and flash
flooding in those islands.


FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 15.6N  21.6W   30 KT  35 MPH
 12H  16/0000Z 16.5N  22.4W   30 KT  35 MPH
 24H  16/1200Z 17.7N  23.4W   30 KT  35 MPH
 36H  17/0000Z 18.5N  24.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  17/1200Z 19.4N  26.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  18/1200Z 21.6N  30.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  19/1200Z...DISSIPATED

$$
Forecaster Stewart

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