Issued at 300 PM CST Sun Sep 20 2026
000 WTPZ42 KNHC 202058 TCDEP2 Tropical Depression Seventeen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP172026 300 PM CST Sun Sep 20 2026 The tropical disturbance to the south of Mexico, formerly Invest 99E, has become better organized with some convective banding features over its eastern semicircle. Although a recent scatterometer pass missed the circulation, low cloud motions indicate that the system now has enough of a low-level circulation to qualify as a tropical depression with an initial intensity of 30 kt this advisory. The center has been difficult to track so far so the initial motion is a rather uncertain 030/7 kt. According to the majority of the track guidance, the system is likely to turn eastward within the next 12 to 24 hours. This motion is apparently due to the system being embedded within a broader cyclonic gyre near the southern coast of Mexico. Later in the forecast period, the system is expected to turn toward the northwest and move on the southern side of a mid-level high. The official forecast is near the northern side of the track guidance model envelope. The depression should be situated within an environment that is conducive for strengthening during the next few days, with very light vertical wind shear, and very warm sea surface temperatures. The official intensity forecast is near the model consensus and shows the system becoming a hurricane in 36 h. It should be noted that the Google DeepMind and HCCA guidance call for even faster strengthening than shown in this initial forecast. Key Messages: 1. Heavy rainfall associated with Tropical Depression 17-E 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 Depression 17-E 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, interest in Mexico should closely monitor its progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 14.9N 104.9W 30 KT 35 MPH 12H 21/0600Z 15.2N 104.2W 40 KT 45 MPH 24H 21/1800Z 15.3N 103.2W 55 KT 65 MPH 36H 22/0600Z 15.2N 102.6W 70 KT 80 MPH 48H 22/1800Z 15.1N 102.1W 85 KT 100 MPH 60H 23/0600Z 15.5N 102.2W 95 KT 110 MPH 72H 23/1800Z 16.4N 103.0W 100 KT 115 MPH 96H 24/1800Z 18.1N 104.9W 100 KT 115 MPH 120H 25/1800Z 19.3N 107.4W 100 KT 115 MPH $$ Forecaster Pasch
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