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Tropical Depression Twenty-One-E Forecast Discussion Number 1
2020-11-17 21:43:01| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Tue Nov 17 2020 916 WTPZ41 KNHC 172042 TCDEP1 Tropical Depression Twenty-One-E Discussion Number 1 NWS National Hurricane Center Miami FL EP212020 300 PM MDT Tue Nov 17 2020 Visible satellite imagery and recent ASCAT data indicate that the circulation of the area of low pressure located well south-southwest of Baja California has become better defined today. The associated convective activity has also become organized in a band around the western and southwestern portions of the circulation. Therefore, the system is being classified as a tropical depression with winds of 30 kt, as indicated by the scatterometer data and a T2.0 (30 kt) Dvorak classification from TAFB. The depression is currently located over SSTs of around 28 deg C, and within a low shear environment. These conditions are conducive for strengthening, but the surrounding mid-level environment is fairly dry which is likely to limit intensification. Most of the intensity guidance calls for the system to become a short-lived tropical storm, and so does the official forecast. After 24 hours, increasing upper-level westerly winds, cooler SSTs, and even less favorable thermodynamic conditions should cause the cyclone to weaken. The system is likely to become a remnant low in about 48 hours, and the global models show it degenerating into a trough of low pressure in 60-72 hours, which is also indicated in the NHC forecast. The initial motion estimate is 285/11 kt. A mid-level ridge that extends westward from northern Mexico over the eastern Pacific should steer the system west-northwestward for the next couple of days. After that time, the cyclone is likely to turn more westward as it weakens and is steered by the low-level trade wind flow. The track guidance is in good agreement, and the NHC forecast is near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 15.2N 113.3W 30 KT 35 MPH 12H 18/0600Z 15.6N 114.9W 35 KT 40 MPH 24H 18/1800Z 16.2N 117.0W 35 KT 40 MPH 36H 19/0600Z 16.7N 119.1W 30 KT 35 MPH 48H 19/1800Z 17.1N 121.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 20/0600Z 17.2N 123.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 20/1800Z...DISSIPATED $$ Forecaster Brown
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