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Tropical Storm Sonia Discussion Number   3
NWS National Hurricane Center Miami FL       EP182025
200 AM PDT Sat Oct 25 2025
 
Satellite imagery shows deep convection expanding over the low-level 
circulation center, with cloud-top temperatures near −80 C. 
Subjective Dvorak Current Intensity estimates from TAFB and SAB are 
in agreement at 2.5/35 kt, which is supported by the latest UW–CIMSS 
objective estimates. Based on the improving satellite presentation 
and these data, the depression has been upgraded to Tropical Storm 
Sonia, with the initial intensity set at 35 kt.
 
Sonia has a brief window of opportunity to gradually strengthen over
the weekend while it remains over warm waters and within a moist,
low-shear environment. Strengthening should level off by Monday as
southwesterly vertical wind shear begins to increase. By Tuesday, a
combination of stronger shear, drier mid- to upper-level air, and
cooler sea-surface temperatures should induce a gradual weakening
trend. Simulated satellite imagery from the global models supports
this scenario, depicting convection diminishing by midweek. As a
result, Sonia is forecast to degenerate into a post-tropical remnant
low by day 4. The NHC intensity forecast remains very similar to the
previous one and continues to closely follow the consensus aids.
 
The initial motion is toward the west, or 275/8 kt, along the
southern side of a subtropical ridge that is expected to persist
through the first half of the weekend. A turn toward the northwest
is anticipated for a brief period late Sunday into early next week
as a weakness develops in the ridge in response to a mid-latitude
trough passing over the northern Pacific. A turn back toward the
west is then expected by Tuesday and into midweek as the ridge
restrengthens to the north. By day 5, Sonia is forecast to become
increasingly influenced by the low-level trade wind flow, which
should steer it southwestward. The latest NHC track forecast remains
close to the previous advisory and lies between the HCCA and
Google DeepMind solutions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0900Z 13.3N 117.6W   35 KT  40 MPH
 12H  25/1800Z 13.4N 118.6W   40 KT  45 MPH
 24H  26/0600Z 13.4N 119.5W   45 KT  50 MPH
 36H  26/1800Z 13.6N 120.4W   50 KT  60 MPH
 48H  27/0600Z 14.1N 121.0W   50 KT  60 MPH
 60H  27/1800Z 14.6N 121.6W   50 KT  60 MPH
 72H  28/0600Z 15.2N 122.4W   45 KT  50 MPH
 96H  29/0600Z 15.5N 125.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  30/0600Z 14.8N 128.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Gibbs (CPHC)
 
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