Tropical Cyclone Discussion
602 WTPZ41 KNHC 131453 TCDEP1 Tropical Depression Twenty-One-E Discussion Number 1 NWS National Hurricane Center Miami FL EP212026 900 AM CST Tue Oct 13 2026 Satellite images show that the area of low pressure located to the south of southern Mexico has become better organized over the past 24 hours. Large areas of banded deep convection are seen to the north and the east of the low-level center. An OSCAT pass from 0630 UTC this morning showed a closed circulation, but it was a bit short of being considered well-defined at that time since the data still showed a broad and somewhat elongated area of weak winds within about 75 n mi of the center. However, the convective organization and curved banding has increased since that time, and the circulation appears to have tightened up a bit over the past several hours. The subjective Dvorak estimate from TAFB is T2.0/30 kt, and it is estimated that a tropical depression has formed with an initial intensity of 30 kt. The initial motion of Tropical Depression Twenty-One-E is estimated to be northwestward, or 305/9 kt. A west-northwestward to northwestward motion should continue over the next 36 hours while a mid-level ridge persists over the northwestern Gulf of America. Thereafter, a turn to the northwest or north-northwest is likely as the ridge weakens. A decrease in forward speed is also expected after day 2 as the cyclone gets caught in weaker steering currents in between the weak ridge to its north and Hurricane Simon to its northwest. Spread in the track forecast is larger than normal from day 3 to 5, and some of this uncertainty is likely also due to uncertainty in Simon's track. A cold front moving southward from Texas into Mexico toward the end of the forecast period could help draw Simon closer to the coastline of Mexico, if the front is potent enough. Regardless, Tropical Depression 21-E could potentially be very close to the coast of Mexico as a hurricane over the weekend, and several Google DeepMind Ensemble members show the cyclone making landfall in southwestern or west-central Mexico. The NHC forecast closely follows the HFIP Corrected Consensus Approach (HCCA), and isn't too far off from the Google DeepMind Ensemble Mean. Confidence in the track forecast is low, especially beyond day 3. The cyclone is forecast to traverse extremely favorable oceanic and atmospheric conditions for at least the next 3 to 4 days. The NHC intensity forecast shows steady strengthening over the next 24 hours as the cyclone works to develop a convective core. After that time, rapid intensification is forecast during the 24 to 72 h time window. The DTOPS in the ECMWF-based SHIPS guidance is forecasting a 74 percent chance of a 65-kt increase over the next 72 h. The NHC intensity forecast is even more aggressive and shows 85 knots of strengthening over the next 72 h. The NHC forecast is slightly below the HCCA and GDMI in the short term, but very near the HCCA and GDMI beyond Day 2. The HAFS-A and HAFS-B models strengthen the cyclone to a category 4, and 36 of the 50 Google DeepMind members make it a category 4 or stronger, so the NHC forecast will aggressively show this system reaching category 4 strength at days 3 and 4. Beyond day 4, the possibility of increasing vertical wind shear and land interaction could induce some weakening, and most of the guidance shows the system losing some intensity after day 4. Confidence in the intensity forecast is above average. We are fairly confident it will become a strong hurricane due to the favorable environmental conditions and model guidance. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 9.8N 96.5W 30 KT 35 MPH 12H 14/0000Z 10.5N 97.6W 40 KT 45 MPH 24H 14/1200Z 11.3N 99.3W 50 KT 60 MPH 36H 15/0000Z 12.0N 100.5W 65 KT 75 MPH 48H 15/1200Z 12.8N 101.4W 80 KT 90 MPH 60H 16/0000Z 13.7N 101.9W 100 KT 115 MPH 72H 16/1200Z 14.5N 102.2W 115 KT 130 MPH 96H 17/1200Z 16.5N 103.5W 120 KT 140 MPH 120H 18/1200Z 18.6N 105.3W 105 KT 120 MPH