[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 152037
TCDAT5

Tropical Depression Fifteen Discussion Number   2
NWS National Hurricane Center Miami FL       AL152023
500 PM AST Fri Sep 15 2023

The depression has lost some convective organization since this
morning, but the low-level circulation appears to be better defined
in recent visible satellite imagery. There are a couple of bursts of
convection just north of the center, but there is a lack of overall
banding at this time.  The initial intensity is held at 30 kt, which
is in agreement with the latest Dvorak Data T-number from TAFB.

The center appears to have reformed to the north since this
morning, which had lead to a rather uncertain initial motion
estimate of 320/11 kt.  The global model guidance suggests that
there could be some additional center reformations during the next
12-24 hours until an inner-core becomes better established.  The
early portion of the track forecast was shifted northward, based on
the farther north initial position.  A deep-layer ridge over the
central Atlantic is expected to steer the system northwestward
during the next several days.  By day 4, a mid-latitude trough
moving over the western Atlantic should allow the cyclone to turn
north-northwestward near the end of the period.  The 12Z dynamical
model guidance made a noticeable eastward shift, and the NHC
forecast has been adjusted in that direction.  The updated track
forecast is close to the consensus aids through 72 hours, but is
along the left side of the model envelope at days 4 and 5.

The depression is likely to only gradually intensify during the
next 12 hours or so as it is still in the formative stage and lacks
inner-core structure.  After that time, a faster rate of
intensification is indicated in the official forecast while the
system remains in an environment of low vertical wind shear and it
traverses warm sea surface temperatures.  The intensity guidance
is somewhat lower this cycle, but the NHC forecast remains generally
the same as before.  This is near the upper-end of the latest
guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 15.4N  44.0W   30 KT  35 MPH
 12H  16/0600Z 16.7N  45.0W   30 KT  35 MPH
 24H  16/1800Z 18.5N  46.6W   40 KT  45 MPH
 36H  17/0600Z 20.4N  48.4W   50 KT  60 MPH
 48H  17/1800Z 22.0N  50.1W   60 KT  70 MPH
 60H  18/0600Z 23.6N  51.7W   70 KT  80 MPH
 72H  18/1800Z 25.1N  53.6W   85 KT 100 MPH
 96H  19/1800Z 28.0N  57.3W  100 KT 115 MPH
120H  20/1800Z 32.0N  59.0W  100 KT 115 MPH

$$
Forecaster Brown
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