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Tropical Depression Twenty-two Forecast Discussion Number 1
2020-09-18 01:00:25| National Hurricane Center (Atlantic)
Issued at 600 PM CDT Thu Sep 17 2020 000 WTNT42 KNHC 172300 TCDAT2 Tropical Depression Twenty-Two Special Discussion Number 1 NWS National Hurricane Center Miami FL AL222020 600 PM CDT Thu Sep 17 2020 Reports from an Air Force Reserve Hurricane Hunter aircraft indicate that the low pressure area over the southwestern Gulf of Mexico has developed a sufficiently well-defined circulation, with SFMR wind data suggesting an intensity of about 30 kt. In addition, the associated convection is organized enough for SAB and TAFB to provide Dvorak satellite intensity estimates of 30 kt. Based on this information, advisories are being initiated on Tropical Depression Twenty-Two. The initial motion is a somewhat uncertain 035/4. During the next 48 h or so, the cyclone should be steered slowly north-northeastward by a mid- to upper-level trough over Texas and northern Mexico. After that time, the global models are in good agreement that this trough will weaken and lift out to the northeast, with a weak mid-level ridge building to the north of the cyclone. This should result in a gradual turn toward the west at a continued slow forward speed. Although the cyclone is relatively close to land, the vast majority of the track guidance keeps the system offshore for the next five days. The official forecast will follow this scenario, with the forecast track being between the HCCA corrected consensus and the other consensus models. The large-scale models suggest that the cyclone will be in an environment of light to moderate vertical wind shear for the next several days. Some dry air entrainment may occur after 48 h. The bulk of the intensity guidance keeps the system below hurricane strength during the forecast period. The official intensity forecast follows the trend of the guidance and shows the system peaking as a tropical storm, but it lies a little above the intensity consensus. As mentioned above, the cyclone is likely to stay offshore during the forecast period. Therefore, it is too early to tell which parts of the coast of the Gulf of Mexico will get wind, storm surge, and rain impacts from this system Key Messages: 1. The system is expected to strengthen to a tropical storm while moving slowly over the western Gulf of Mexico during the next few days. 2. While it is too early to determine what areas could see direct wind, storm surge, and rainfall impacts from this system, interests throughout the western Gulf of Mexico should monitor the progress of this system and future updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 17/2300Z 21.9N 94.3W 30 KT 35 MPH 12H 18/0600Z 22.7N 94.0W 30 KT 35 MPH 24H 18/1800Z 23.8N 93.5W 35 KT 40 MPH 36H 19/0600Z 24.8N 93.0W 45 KT 50 MPH 48H 19/1800Z 25.4N 92.9W 55 KT 65 MPH 60H 20/0600Z 25.8N 93.1W 60 KT 70 MPH 72H 20/1800Z 26.1N 93.8W 60 KT 70 MPH 96H 21/1800Z 26.1N 95.1W 55 KT 65 MPH 120H 22/1800Z 25.6N 96.1W 50 KT 60 MPH $$ Forecaster Berg/Beven
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