855 
WTPZ44 KNHC 240851
TCDEP4
 
Tropical Storm Iselle Discussion Number   4
NWS National Hurricane Center Miami FL       EP092026
200 AM PDT Mon Aug 24 2026
 
Iselle is being affected by northwesterly shear, with much of the 
deep convection displaced to the south and east of the center. Over 
the past several hours, the convective structure has evolved, with 
curved banding becoming increasingly established around the center. 
The latest Dvorak intensity estimate from TAFB at 0600 UTC was 
3.0/45 kt; however, recent objective intensity estimates from 
UW-CIMSS have increased and range from 43-59 kt. Given the improved 
banding evident on satellite imagery and the upward trend in 
objective intensity estimates, the initial intensity is set at 50 kt 
for this advisory. 

The tropical storm is moving northwestward around 10 kt, steered by 
a mid-level ridge centered over the southwestern United States. 
Iselle is forecast to turn toward the west-northwest as the ridge 
expands westward into the eastern Pacific, and this general motion 
is expected through much of this week. The latest NHC forecast is 
very similar to the previous advisory and lies near the middle of 
the track guidance envelope, closest to the HFIP Corrected Consensus 
(HCCA) and the Google DeepMind (GDMI) model. There is considerable 
spread among the guidance during the latter portion of the forecast 
period, resulting in slightly below-average confidence in the track 
forecast. 

Iselle is moving over warm waters around 29-30 C and remains within 
a fairly moist mid-level environment, which should support gradual 
strengthening during the next 12-24 h. The latest NHC forecast 
brings Iselle to hurricane strength during this period, near the 
upper end of the intensity guidance, and is consistent with HCCA and 
GDM. Beyond 24 h, increasing wind shear, cooler waters and 
progressively drier mid-level air are expected to lead to gradual 
weakening from Tuesday through the remainder of the week. The ECMWF 
and GFS simulated satellite imagery suggest that Iselle may struggle 
to maintain organized convection by late this week, raising the 
possibility that the cyclone could become post-tropical earlier than 
currently forecast. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 17.8N 116.2W   50 KT  60 MPH
 12H  24/1800Z 19.0N 117.4W   60 KT  70 MPH
 24H  25/0600Z 20.1N 118.9W   65 KT  75 MPH
 36H  25/1800Z 20.9N 120.7W   60 KT  70 MPH
 48H  26/0600Z 21.5N 122.5W   55 KT  65 MPH
 60H  26/1800Z 21.9N 124.4W   50 KT  60 MPH
 72H  27/0600Z 22.4N 126.3W   45 KT  50 MPH
 96H  28/0600Z 23.1N 130.1W   35 KT  40 MPH
120H  29/0600Z 23.9N 134.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Adams