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Tropical Storm Iselle Discussion Number  12
NWS National Hurricane Center Miami FL       EP142020
200 AM PDT Sat Aug 29 2020
 
Iselle has become less organized during the past several hours.
The low-level center is exposed to the east of a decaying and
disheveled area of deep convection.  An ASCAT-B overpass from around
0430 UTC showed maximum winds in the 40-45 kt range, but since the
system's appearance has degraded since that time, the initial
intensity is set at 40 kt.  This value is also in agreement
with an average of the latest satellite intensity estimates, which
range from 33 to 45 kt. Iselle is feeling the effects of about 25 kt
of easterly vertical wind shear.  Since the shear is expected to
remain strong while Iselle heads for cooler waters and a drier air
mass, steady weakening is anticipated.  Iselle will likely become a
tropical depression by tonight and a remnant low on Sunday. Most of
the models show the remnant low dissipating in 3 days, and so does
the official forecast.
 
The compact tropical storm is moving northward at about 5 kt.  A
continued northward motion is expected for another day or so,
followed by a turn to the northwest when Iselle becomes a weak and
shallow system and moves in the low-level flow.  The new NHC track 
forecast is a little to the east of the previous one to come into 
better agreement with the latest consensus aids.
 
The initial 34-kt wind radii have been modified slightly based on
the aforementioned ASCAT data.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0900Z 19.7N 115.1W   40 KT  45 MPH
 12H  29/1800Z 20.7N 114.9W   35 KT  40 MPH
 24H  30/0600Z 22.2N 114.9W   30 KT  35 MPH
 36H  30/1800Z 23.5N 115.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  31/0600Z 24.5N 115.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  31/1800Z 25.3N 116.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  01/0600Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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