Tropical Cyclone Discussion

365
WTPZ44 KNHC 240245
TCDEP4
 
Tropical Storm Iselle Discussion Number   3
NWS National Hurricane Center Miami FL       EP092026
800 PM PDT Sun Aug 23 2026
 
The most recent ASCAT and OSCAT passes have shown that the strongest 
winds with Iselle are around 40 to 45 kt. UW-CIMSS objective 
estimates are in the 35-55 kt range, and the most recent TAFB 
subjective Dvorak estimate is T3.0/45 kt. With all of that data in 
consideration, the intensity has been held at 45 kt for this 
advisory. However, recent observations at Isla Clarion have recorded 
sustained winds around 30 to 35 kt, gusting up to around 40 kt and 
a surface pressure of 1002 mb. Thus in light of that data, the 
central pressure for Iselle has been lowered to 999 mb.
 
The initial motion estimate is northwestward, or 310 degrees at 8 
kt.  A continued northwestward motion is expected through Monday 
while Iselle is steered by ridging over the southwestern United 
States and northwestern Mexico. As the ridge builds in some more to 
the north of the cyclone, a gradual turn toward the west-northwest 
is expected on Tuesday and Wednesday.  The current NHC track is very 
similar to the previous track, only minor adjustments in speed and 
location have been made. The track remains very close to the lastest 
HFIP Corrected Consensus (HCCA) model and the Google DeepMind 
(GDMI). There is a good amount of spread in the track forecast 
towards the later portion of the forecast, thus the confidence 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. The current NHC intensity forecast is on the higher 
end of the guidance, thus it is possible that Iselle might not quite 
make it to hurricane status. After this period, the cyclone will 
move into a more hostile environment with stronger shear, colder 
sea-surface temperatures, and some slightly drier air. As such, the 
storm should progressively get weaker beyond a couple of days. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0300Z 17.1N 115.3W   45 KT  50 MPH
 12H  24/1200Z 18.1N 116.4W   50 KT  60 MPH
 24H  25/0000Z 19.4N 117.8W   60 KT  70 MPH
 36H  25/1200Z 20.4N 119.6W   65 KT  75 MPH
 48H  26/0000Z 21.0N 121.4W   60 KT  70 MPH
 60H  26/1200Z 21.5N 123.1W   55 KT  65 MPH
 72H  27/0000Z 21.9N 125.1W   50 KT  60 MPH
 96H  28/0000Z 22.8N 128.8W   40 KT  45 MPH
120H  29/0000Z 23.6N 132.5W   30 KT  35 MPH...POST-TROP/REMNT LOW