000
WTPZ44 KNHC 232032
TCDEP4
 
Tropical Storm Iselle Discussion Number   2
NWS National Hurricane Center Miami FL       EP092026
200 PM PDT Sun Aug 23 2026

Recent satellite imagery over Iselle shows a shear pattern, with a 
large area of very deep convection located in the southwest 
semicircle of Iselle.  Visible imagery shows a partially exposed 
low-level center at the northeast edge of the convection.  A recent 
23/1748Z ASCAT-C overpass shows an elongated, but well-defined 
surface circulation, with a radius of maximum winds (RMW) of about 
70 nautical miles, with gales in the NE, SE and SW quadrants.  There 
are several 40-45 kt vectors on the south side, and the intensity is 
increased to 45 kt for this advisory.  This is above the latest 
subjective Dvorak estimate from TAFB, which is T2.5/35 kt.

The initial motion estimate is northwestward, or 315 degrees at 14 
kt.  A continued northwest motion is expected through Monday while 
Iselle is steered by ridging over the southwestern United States and 
northwestern Mexico. As the ridge builds in a bit more to the north 
of the cyclone, a gradual turn toward the west-northwest is expected 
on Tuesday and Wednesday.  The NHC track forecast has been shifted 
well to the right (or northeast) of the previous forecast through 48 
h, mainly due to the farther north initial position and is nearly on 
top of the previous forecast thereafter.  The NHC forecast is very 
close to the latest HFIP Corrected Consensus (HCCA) model and the 
Google DeepMind (GDMI).  There is still a healthy amount of spread 
in the track guidance, and confidence in the track forecast is 
slightly below average.
 
Iselle will be traveling over warm water and within a moist 
environment with weak to moderate vertical wind shear for the next 
day or so, but westerly vertical wind shear should increase to the 
15-20 kt range by Tuesday or sooner.  Strengthening is expected for 
the next 36 h.  Thereafter, Iselle will be moving into a more 
stable environment, with gradually decreasing sea-surface 
temperatures, so weakening is expected to begin by Tuesday night 
or Wednesday.  Only small changes have been made to the NHC 
intensity forecast, which lies between the middle and high end of 
the guidance envelope for most of the forecast period.  Rapid 
intensification is becoming less likely because the RMW is still
large, and the system has at most 36-48 h left to strengthen.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/2100Z 16.9N 115.1W   45 KT  50 MPH
 12H  24/0600Z 18.2N 116.3W   50 KT  60 MPH
 24H  24/1800Z 19.6N 117.8W   60 KT  70 MPH
 36H  25/0600Z 20.8N 119.4W   65 KT  75 MPH
 48H  25/1800Z 21.4N 121.1W   65 KT  75 MPH
 60H  26/0600Z 21.9N 122.8W   60 KT  70 MPH
 72H  26/1800Z 22.4N 124.6W   50 KT  60 MPH
 96H  27/1800Z 23.3N 128.4W   45 KT  50 MPH
120H  28/1800Z 24.2N 132.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Hagen