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Tropical Storm Iselle Discussion Number   6
NWS National Hurricane Center Miami FL       EP142020
200 PM PDT Thu Aug 27 2020
 
Since the previous advisory, a new burst of deep convection 
developed near the center of Iselle the persisted for much of the 
morning. It was not until recently that the easterly shear has begun 
to push the convection to the west of the center. The latest Dvorak 
estimates from TAFB and SAB as well as data from a recent ASCAT 
overpass all agree that the initial intensity has increased to 45 
kt. Moderate-to-strong easterly to northeasterly vertical wind shear 
should prevent Iselle from further strengthening over the next 
couple of days. After that time, the shear is forecast to relax 
somewhat. However, by that time 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 late this weekend into early next 
week before degenerating into a remnant low. The latest NHC 
intensity forecast is close to the LGEM guidance.
 
Iselle continues moving northeastward at 4 kt, embedded in a large
monsoon gyre. The steering flow is forecast to become more
southeasterly this weekend inside the gyre, resulting in a gradual
turn to the northwest. As the cyclone breaks north of the gyre and
becomes shallow, a turn to the west is anticipated while the system
becomes steered by a low- to mid- level ridge to its north. The
latest NHC track forecast was nudged just a little to the right of
the previous one due to a shift in the guidance, and lies in between
the previous forecast and the various track consensus aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/2100Z 17.2N 115.8W   45 KT  50 MPH
 12H  28/0600Z 17.8N 115.3W   45 KT  50 MPH
 24H  28/1800Z 18.6N 114.7W   45 KT  50 MPH
 36H  29/0600Z 19.6N 114.4W   40 KT  45 MPH
 48H  29/1800Z 20.8N 114.3W   35 KT  40 MPH
 60H  30/0600Z 21.9N 114.6W   30 KT  35 MPH
 72H  30/1800Z 22.8N 115.4W   25 KT  30 MPH
 96H  31/1800Z 23.2N 116.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  01/1800Z 23.1N 117.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Latto
 
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