Hurricane Simon

821 
WTPZ45 KNHC 121459
TCDEP5
 
Hurricane Simon Discussion Number  21
NWS National Hurricane Center Miami FL       EP202026
800 AM MST Mon Oct 12 2026
 
Simon's interaction with the coast of Mexico has made it a very 
compact hurricane. The satellite presentation this morning consists 
of a very small central dense overcast with a warm spot in the 
center which still appears to be a small eye. The convection is also 
very electrically active, with substantial lightning occurring in 
the eastern eyewall. A 1110 UTC GPM microwave pass showed that 
Simon's inner core remains intact, though with the eye open on the 
northwest side. This structure is consistent with some mid-level 
easterly shear that appears to be undercutting the outflow layer, 
looking at some area-average soundings from the HAFS-A/B 
initialization this morning. Satellite intensity estimates have a 
large range this morning, as low as CI 4.1/67 kt from the UW-CIMSS 
ADT, or as high as CI 5.5/102 kt from the latest subjective Dvorak 
fix. The initial intensity is lowered slightly to 95 kt for this 
advisory, favoring a blend of the latest SATCON (100 kt) and D-MINT 
(85-90 kt) estimates.
 
Based on satellite images, Simon continues to move very slowly to 
the northwest, with an estimated motion of 315 degrees at 3 kt. This 
very slow motion is the result of competing steering influences from 
a distant mid-level ridge centered over the Texas Gulf coast, and 
another weaker mid-level ridge placed southwest of Simon over the 
eastern Pacific. In general the steering imparted by the ridge to 
the northwest should be a little stronger, and thus Simon is 
expected to maintain a very slow northwestward motion over the next 
24-36 h. After that period, a large trough with an embedded 
short-wave is expected to amplify and move into the southwestern 
United States, and this trough is expected to extend far enough 
southward to impart a little more westerly flow that should 
ultimately turn Simon to the north-northeast in the 48-72 hour time 
frame. With that said, the track guidance is not at all in agreement 
on how quickly this turn will occur. The latest 06 UTC GFS and 
HAFS-A/B runs almost immediately move Simon northward and then 
north-northeast, resulting in a much faster landfall back in 
mainland Mexico. By contrast, the 06 UTC ECMWF run shows a 
short-term westward track that meanders offshore to the southeast of 
the Baja California Peninsula before it turns northward and moves up 
into the Gulf of California. The ensemble guidance is also all over 
the place, resembling a squashed spider with substantial spread from 
the southwest to northeast direction. The latest NHC track forecast 
has been shifted westward and is quite a bit slower, following the 
latest trends in the track guidance. However, this track is not 
nearly as slow or as far west as the latest Google DeepMind ensemble 
mean (GDMI) or its newer Weather Next Model (WN3I). Given the large 
spread in solutions, this remains a low confidence track forecast.
 
Based on the earlier microwave images, Simon still appears to have a
small inner core, and that is an important consideration to take
into account in the forecast over the next few days. While the
hurricane appears to be currently dealing with some mid-level
easterly shear and that may result in a little more short-term
weakening, this shear is expected to subside over the next 24 h as
Simon traverses very warm 30-31 C sea-surface temperatures. In fact,
the latest HMON and HAFS-A/B runs show the small core of Simon
recovering and re-intensifying back into a major hurricane later
this week. Thus, the latest NHC intensity forecast starts to show
some restrengthening after 24 h. Small storms like Simon can also
be prone to rapid changes in intensity, both up or down, which
makes the intensity forecast also more uncertain than usual. This
forecast is initially close to the middle of the guidance but ends
up on the higher side after 48 h. Rapid weakening is still
anticipated when Simon eventually makes landfall later this week
towards the end of the forecast.
 
Key Messages:
 
1. Tropical Storm winds are still likely along a portion of the
west-central coast of Mexico for a few more hours, where a Tropical
Storm Warning is in effect.
 
2. Simon is expected to approach the coast of western Mexico later
this week, where hurricane conditions are possible. A Hurricane
Watch is in effect from Cabo Corrientes to Bahia Tempehuaya.
 
3. Heavy rainfall associated with Simon will impact portions of
southwestern and 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 few days. These swells
are likely to cause life-threatening surf and rip current
conditions. Please consult products from your local weather office.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/1500Z 20.1N 106.5W   95 KT 110 MPH
 12H  13/0000Z 20.4N 106.8W   85 KT 100 MPH
 24H  13/1200Z 20.9N 107.3W   80 KT  90 MPH
 36H  14/0000Z 21.3N 107.7W   85 KT 100 MPH
 48H  14/1200Z 21.6N 107.7W   90 KT 105 MPH
 60H  15/0000Z 22.2N 107.4W   90 KT 105 MPH
 72H  15/1200Z 23.2N 106.9W   90 KT 105 MPH
 96H  16/1200Z 24.1N 106.3W   45 KT  50 MPH...INLAND
120H  17/1200Z...DISSIPATED
 
$$
Forecaster Papin