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Tropical Storm Priscilla Discussion Number   1
NWS National Hurricane Center Miami FL       EP162025
200 PM MST Sat Oct 04 2025
 
The satellite presentation of Invest 99E has continued to improve 
today, with an elongated convective band having formed through 
the western and northern part of the circulation.  Given the 
system’s broad nature, its center definition had been questionable, 
particularly based on ASCAT data from yesterday evening.  However, a 
recent 1645 UTC ASCAT pass showed that the center has become 
significantly better defined, with 35-40 kt winds occurring north 
and northwest of the center.  Based on these data, advisories are 
being initiated on Tropical Storm Priscilla, with an estimated 
intensity of 40 kt.

Priscilla is moving northwestward (315 degrees) at 8 kt.  A 
large-scale trough is currently located over the western United 
States and extends southward over Baja California, leaving 
Priscilla in an environment of weak steering currents.   In the 
short term, that should cause the storm to slow down and drift in a 
general northward direction for the next 36 hours.  After that 
time, Priscilla is expected to settle in to a more steady 
northwestward track as a stronger mid-level ridge builds over 
northern Mexico and the deep-layer trough remains entrenched over 
the western United States.  For most of the forecast period, the 
NHC track forecast leans on the eastern side of the guidance 
envelope, in the vicinity of the ECMWF, HCCA consensus aid, and 
Google DeepMind ensemble mean.

Priscilla will be moving over sea surface temperatures of about 29 
degrees Celsius during the next couple of days, coincident with a 
period of strong upper-level divergence.  These conditions should 
support strengthening, although the system's large size could limit 
the rate of intensification in the short term.  That said, some of 
the Rapid Intensification (RI) indices are greater than 50% within 
36 and 48 hours, so if Priscilla can develop a tighter inner core 
within the larger wind field, more significant strengthening would 
be possible.  The NHC intensity forecast calls for Priscilla to 
become a hurricane by Sunday night, with strengthening continuing 
through Tuesday.  Cooler water temperatures and a less favorable 
atmosphere should induce weakening by Wednesday and Thursday.

 
KEY MESSAGES:

1.  Tropical storm conditions are possible along portions of the 
coast of southwestern Mexico within the watch area Sunday and 
Monday.  Interests in the southern portion of Baja California Sur 
should also monitor the progress of Priscilla.

2.  Heavy rainfall associated with Priscilla will impact coastal 
sections of southwestern Mexico through Monday, which could result 
in flash flooding, particularly in areas of higher terrain.

3.  Swells generated by Priscilla are affecting portions of
the coast of southwestern Mexico and will reach the coasts of 
west-central Mexico and the southern Baja California peninsula by 
Monday.  These swells are likely to cause life-threatening surf and 
rip current conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 15.5N 106.6W   40 KT  45 MPH
 12H  05/0600Z 15.8N 106.8W   45 KT  50 MPH
 24H  05/1800Z 16.3N 106.9W   55 KT  65 MPH
 36H  06/0600Z 17.0N 107.3W   65 KT  75 MPH
 48H  06/1800Z 17.8N 108.2W   75 KT  85 MPH
 60H  07/0600Z 18.8N 109.4W   80 KT  90 MPH
 72H  07/1800Z 19.7N 110.7W   85 KT 100 MPH
 96H  08/1800Z 21.7N 113.3W   80 KT  90 MPH
120H  09/1800Z 24.1N 115.4W   60 KT  70 MPH
 
$$
Forecaster Berg
 
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