Advisories

000
WTPZ45 KNHC 130842
TCDEP5
 
Hurricane Simon Discussion Number  24
NWS National Hurricane Center Miami FL       EP202026
200 AM MST Tue Oct 13 2026
 
Simon remains a very small hurricane. Synthetic aperture radar (SAR) 
data from around 01 UTC showed its compact wind field, with a 5-n-mi 
radius of maximum wind and tropical-storm-force winds that extended 
only 30-40 n mi from the center. Satellite images reveal Simon has 
maintained a small central dense overcast tonight, with a sharper 
edge to the cloud tops on the northeastern side, perhaps the result 
of some vertical wind shear. Given the small size of Simon, it is 
possible that conventional satellite estimates are struggling to 
represent its true intensity. The initial intensity is set at 80 kt, 
which lies in between the latest Dvorak CI number from TAFB (4.5/77 
kt) and the earlier SAR data. 
 
The hurricane is moving slowly northwestward (310/3 kt) around a 
subtropical ridge over the southern United States. During the next 
couple of days, Simon is forecast to become caught in weak steering 
currents between this ridge and another ridge that should build to 
the northwest over the eastern Pacific. As a result, most of the 
track guidance now shows little net motion of the storm through 60 
h, although Simon meanders in several different directions in the 
various global models and ensembles. Given the lack of a clear model 
signal, the new NHC forecast attempts to maintain some continuity by 
using a blend of the latest Google DeepMind, AI-GFS, and ECMWF track 
aids through 72 h. Once again, the trend is slower and farther west 
than the previous prediction. A general northward motion is shown at 
96-120 h as the system (if it survives that long) should become 
steered by a cutoff upper low to its northwest. Needless to say, the 
lack of model agreement makes this a very low confidence forecast.

Simon's intensity forecast is also very challenging and highly 
sensitive to its uncertain track. The small system is forecast to be 
within a generally low shear environment over very warm SSTs for the 
next couple of days. However, the slow forward speed of Simon could 
lead to upwelling of cooler waters, and its proximity to land could 
make it susceptible to intrusions of drier air from mainland Mexico. 
Much of the guidance shows little intensity change or even some 
weakening through midweek, and the NHC forecast remains on the 
higher end of the intensity guidance. By Thursday, the model 
consensus favors more steady weakening through the rest of the 
period due to increased vertical wind shear, and the latter half of 
the NHC forecast has been lowered notably from the previous one.

It is worth emphasizing that this is a very low confidence forecast, 
and interests in west-central Mexico should continue to closely 
monitor the latest updates. Changes to watches and warnings may 
be required later today based on the latest forecast trends.

 
Key Messages:
 
1. Hurricane conditions are likely on Las Islas Marias over the
next day or so, where a Hurricane Warning remains in effect.
 
2. Simon could approach the coast of western Mexico later this 
week at or near hurricane strength, and a Hurricane Watch remains 
in effect for a portion of the area.
 
3. Heavy rainfall associated with Simon will impact portions of 
west-central Mexico over the next few days. This rainfall will 
produce life-threatening flooding and mudslides, especially in areas 
of steep terrain.
 
4. Large swells will affect portions of the southwestern and
west-central coasts of Mexico over the next several days. These
swells are likely to cause life-threatening surf and rip current
conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0900Z 20.6N 107.2W   80 KT  90 MPH
 12H  13/1800Z 20.7N 107.4W   75 KT  85 MPH
 24H  14/0600Z 20.9N 107.7W   75 KT  85 MPH
 36H  14/1800Z 21.0N 107.8W   75 KT  85 MPH
 48H  15/0600Z 21.2N 107.9W   75 KT  85 MPH
 60H  15/1800Z 21.8N 108.0W   70 KT  80 MPH
 72H  16/0600Z 23.0N 108.1W   65 KT  75 MPH
 96H  17/0600Z 24.2N 108.1W   55 KT  65 MPH
120H  18/0600Z 25.4N 108.2W   30 KT  35 MPH...POST-TROP/INLAND
 
$$
Forecaster Reinhart