Tropical Cyclone Discussion

200
WTPZ44 KNHC 251444
TCDEP4
 
Tropical Storm Iselle Discussion Number   9
NWS National Hurricane Center Miami FL       EP092026
800 AM PDT Tue Aug 25 2026

Iselle continues to produce a large area of deep convection near 
and well northeast of the center.  A GCOM-AMSR2 microwave 
pass from a few hours ago showed that the system is on the edge of 
the convective mass, and the low-level center is displaced to the 
southwest of the mid-level circulation.  Satellite estimates support 
keeping Iselle a 60-kt tropical storm for this advisory.  Gradual 
weakening is anticipated during the next few days due to persistent 
westerly shear, cooling waters and a dry mid-level atmosphere. 
Iselle should lose all deep convection in about 2 days due to a
hostile environment, and post-tropical status is anticipated after 
that time.  Model guidance is in very good agreement on the slow 
decay, and no significant changes were made to the last NHC 
forecast.

Microwave fixes indicate that Iselle has turned, and is now moving 
west-northwestward at about 9 kt.  This general heading should 
continue for the next couple of days due to ridging extending from 
the southern United States.  As the storm weakens, it should turn 
more westward by day 3 due to the cyclone becoming steered more by 
the low-level flow.  There has been a modest leftward shift in the 
guidance, consistent with a weakening system, so the new forecast is 
shifted to the left, lying between the NOAA corrected-consensus 
model HCCA and the Google DeepMind ensemble mean.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/1500Z 20.9N 121.1W   60 KT  70 MPH
 12H  26/0000Z 21.4N 122.5W   55 KT  65 MPH
 24H  26/1200Z 22.0N 124.1W   45 KT  50 MPH
 36H  27/0000Z 22.7N 126.0W   40 KT  45 MPH
 48H  27/1200Z 23.3N 127.9W   35 KT  40 MPH
 60H  28/0000Z 23.8N 129.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  28/1200Z 24.2N 131.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  29/1200Z...DISSIPATED