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Tropical Storm Iselle Discussion Number   5
NWS National Hurricane Center Miami FL       EP142020
800 AM PDT Thu Aug 27 2020

Iselle consists of a rather ragged looking area of deep convection 
being sheared to the southwest of a partially exposed low-level 
center. A blend of the latest satellite intensity estimates from 
TAFB and UW-CIMSS support keeping the initial intensity at 40 kt. 
Moderate-to-strong easterly to northeasterly vertical wind shear 
will likely prevent Iselle from strengthening over the next couple 
of days. After that time, the shear is forecast to relax somewhat. 
However, the cyclone will then be moving over SSTs of only 26 C and 
into a more stable atmospheric environment. This should cause the 
deep convection to gradually dissipate, and the cyclone is expected 
to weaken this weekend before degenerating into a remnant low early 
next week. The latest NHC intensity forecast is a blend of the IVCN 
consensus and SHIPS guidance. 
 
Iselle is moving northeastward at 4 kt, embedded in a large monsoon 
gyre. The steering flow is forecast to become more southerly this 
weekend inside the gyre, resulting in a more northward motion. As 
the cyclone breaks north of the gyre, a turn to the northwest then 
west is anticipated while the system becomes steered by a low- to 
mid- level ridge to its north. The latest NHC track forecast is 
little changed from the previous one, and lies in between the HFIP 
corrected consensus HCCA and the TVCX track consensus.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/1500Z 17.0N 115.8W   40 KT  45 MPH
 12H  28/0000Z 17.5N 115.4W   40 KT  45 MPH
 24H  28/1200Z 18.2N 115.0W   40 KT  45 MPH
 36H  29/0000Z 18.9N 114.6W   40 KT  45 MPH
 48H  29/1200Z 19.9N 114.2W   40 KT  45 MPH
 60H  30/0000Z 21.2N 114.4W   35 KT  40 MPH
 72H  30/1200Z 22.2N 115.3W   30 KT  35 MPH
 96H  31/1200Z 22.5N 116.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  01/1200Z 22.3N 117.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Latto
 
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