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Tropical Storm Sonia Discussion Number   6
NWS National Hurricane Center Miami FL       EP182025
800 PM PDT Sat Oct 25 2025
 
Sonia seems to be holding steady this evening.  Data from a 
microwave satellite overpass showed the circulation was still open 
to the west, with a curved band wrapped around the eastern and 
southern portions of the storm.  Convection has waned during the 
past few hours and objective and subjective satellite intensity 
estimates have remained generally stable.  The initial intensity is 
held at 45 kt for this advisory.
 
The storm is moving westward at 4 kt.  There is still a large spread 
in the model guidance through the forecast period.  The forecast 
reasoning has not changed.  A steadily strengthening system is 
expecting to turn west-northwestward to northwestward.  The model 
forecasts with shallower vortex structures tend to remain on a more 
westward trajectory while the deeper cyclones tend to track more 
poleward.  The primary steering features influencing Sonia are a 
subtropical ridge extending to the north of the tropical storm and 
an amplifying mid-latitude trough that is expected to erode the 
ridge in the coming days.  The latest NHC track forecast is similar 
to the previous prediction and lies south of the corrected consensus 
aid and north of the Google DeepMind ensemble mean.

Sonia has about a day or so to gradually strengthen before 
atmospheric and oceanic conditions begin to significantly inhibit 
intensification.  After that time, vertical wind shear is expected 
to increase, with sea surface temperatures decreasing, particularly 
if Sonia takes a more northern path. The model guidance envelope 
shifted noticeably lower this cycle, though only minimal changes 
were made to the official intensity forecast. The latest prediction 
lies near the top of the guidance, close to HAFS-A, peaking in about 
36 hours, and then calls for Sonia to become a post-tropical cyclone 
by day 3.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0300Z 13.5N 119.3W   45 KT  50 MPH
 12H  26/1200Z 13.5N 119.8W   50 KT  60 MPH
 24H  27/0000Z 13.8N 120.4W   55 KT  65 MPH
 36H  27/1200Z 14.2N 121.3W   60 KT  70 MPH
 48H  28/0000Z 14.7N 122.3W   55 KT  65 MPH
 60H  28/1200Z 14.9N 123.8W   45 KT  50 MPH
 72H  29/0000Z 15.0N 125.4W   35 KT  40 MPH...POST-TROPICAL
 96H  30/0000Z 14.8N 128.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  31/0000Z...DISSIPATED
 
$$
Forecaster Bucci
 
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