Advisories

000
WTPZ42 KNHC 210247
TCDEP2
 
Tropical Storm Polo Discussion Number   2
NWS National Hurricane Center Miami FL       EP172026
900 PM CST Sun Sep 20 2026
 
After a brief hiccup in the convective structure on satellite 
imagery this evening, several convective bursts have formed close 
to the estimated center of circulation. Earlier microwave images 
showed a decent low-level structure, though there was some 
eastward tilt with height. The 00 UTC Dvorak intensity estimate 
from TAFB was up to T3.0/45 kt, but the objective intensity 
estimates from UW-CIMSS were lower in the 29-39 kt range. Still, 
these values are enough support to increase the winds to 35 kt, 
making the depression Tropical Storm Polo. 

It remains tricky to find the center this evening, but my best guess 
is that the center is close to the ongoing convective burst and is 
estimated to be moving east-northeastward or 075 degrees at 4 kt. 
Over the next 24-36 h, Polo will likely be influenced by the 
steering of low- to mid-level ridging south of the cyclone, with 
most of the track guidance showing a slow eastward or 
east-southeastward motion on Monday. On Tuesday, mid-level ridging 
over Texas and Mexico is forecast to build in, and the track 
guidance responds to this change by showing a sharp, hairpin turn to 
the northwest that continues through the remainder of the forecast 
period. The NHC track forecast is close to the prior one, though 
shows a bit of a sharper turn in 48-60 h, and is a little to the 
south and west thereafter. This track forecast roughly splits the 
difference between the reliable HFIP Corrected Consensus Approach 
(HCCA) and Google DeepMind ensemble mean (GDMI) aids. It is worth 
noting some of the hurricane-regional models are further east, and 
short-term trends will be monitored in the guidance over the next 
day or so to see if any eastward adjustments are needed. Towards the 
end of the forecast, it is possible Polo may get close enough to the 
circulation of Odalys to interact, and there is significant track 
uncertainty in 5 days. 

Intensity-wise there appear to be few impediments in Polo's 
forecast, with low shear under 10 kt, very warm 31 C sea-surface 
temperatures, and abundant deep-layer moisture.  While it may take 
another 12 h or so for Polo to develop an inner core, its possible 
the ongoing convective burst near the center is already initiating 
that process. The intensity guidance is rather aggressive, with all 
of the hurricane-regional models showing various degrees of rapid 
intensification over the next 2-3 days in addition to the HCCA and 
GDMI guidance. Thus, the NHC intensity forecast will also show rapid 
intensification in the 24-60 h period, and now shows Polo becoming a 
Category 4 hurricane in 72 h. Remarkably, this is still under the 
latest HCCA and GDMI intensity in that time frame and its possible 
future upward intensity adjustments will be needed. Thereafter, 
inner-core fluctuations will likely govern the intensity of Polo in 
the 3-5 day time frame, but Polo is still likely to be a major 
hurricane through the end of the forecast period. 

 
Key Messages:
1. Heavy rainfall associated with Tropical Storm Polo will impact 
coastal portions of southwest Mexico this week. This rainfall may 
produce life-threatening flooding and mudslides, especially in areas 
of steep terrain.
 
2. Tropical Storm Polo is forecast to strengthen and move closer to 
the southwestern Mexican coast as a major hurricane later this week. 
Although it is too soon to determine the exact location or magnitude 
of impacts associated with the system, interests in Mexico should 
closely monitor its progress and updates to the forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 15.1N 104.6W   35 KT  40 MPH
 12H  21/1200Z 15.4N 103.8W   45 KT  50 MPH
 24H  22/0000Z 15.4N 103.1W   60 KT  70 MPH
 36H  22/1200Z 15.2N 102.4W   80 KT  90 MPH
 48H  23/0000Z 15.5N 102.4W   95 KT 110 MPH
 60H  23/1200Z 16.0N 103.0W  110 KT 125 MPH
 72H  24/0000Z 16.7N 103.7W  115 KT 130 MPH
 96H  25/0000Z 18.2N 106.0W  115 KT 130 MPH
120H  26/0000Z 19.5N 109.5W  115 KT 130 MPH
 
$$
Forecaster Papin