[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 010835
TCDAT5

Tropical Depression Fifteen Discussion Number   3
NWS National Hurricane Center Miami FL       AL152020
500 AM EDT Tue Sep 01 2020

Deep convection remains displaced to the east and southeast of the
depression's low-level center due to increasing west-northwesterly
shear.  Maximum winds are still estimated to be 30 kt, with no
appreciable structural changes having occurred since last evening's
ASCAT pass, which showed 25-30 kt winds.

The initial motion is toward the northeast, or 050/11 kt, with the
depression becoming embedded in the mid-latitude westerlies north
of the subtropical ridge.  Forecast guidance agrees that the
cyclone will turn east-northeastward and then eastward during the
next 2-3 days, moving farther out into the Atlantic, although there
is greater-than-normal spread among the track models mainly due to
speed differences.  In particular, the ECMWF is one of the fastest
models, while the GFS and UKMET hang the cyclone back to the west a
little longer.  Since many of the consensus aids, including HCCA,
are closer to the faster model solutions, the NHC track forecast
leans toward the quicker side of things.

UW-CIMSS analyses indicate that the shear has increased to 20-25
kt, and it's only expected to get stronger from here.  Some slight
strengthening of the depression can't be ruled out during the next
12-24 hours while the shear vector is aligned with the storm motion,
but by this time tomorrow the shear is likely to be as strong as
35-45 kt out of the northwest.  Therefore, little change in
strength is now indicated in the official forecast for the next day
or two.  The shear magnitude is expected to peak in about 48 hours,
and the depression is forecast to be a remnant low at that point,
if it hasn't become one already.  The GFS dissipates the low in
about 48 hours, but since the other models hang onto it a little
bit longer, the NHC forecast shows dissipation by day 5.


FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 34.1N  74.4W   30 KT  35 MPH
 12H  01/1800Z 35.0N  72.5W   30 KT  35 MPH
 24H  02/0600Z 36.0N  69.7W   30 KT  35 MPH
 36H  02/1800Z 36.9N  67.0W   30 KT  35 MPH
 48H  03/0600Z 37.5N  63.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  03/1800Z 37.7N  61.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  04/0600Z 37.8N  58.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  05/0600Z 39.2N  53.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  06/0600Z...DISSIPATED

$$
Forecaster Berg
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