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| #1019928 (Received by flhurricane at: 10:51 PM 04.Oct.2020) TCDAT1 Tropical Depression Twenty-Six Discussion Number 2 NWS National Hurricane Center Miami FL AL262020 1100 PM EDT Sun Oct 04 2020 Satellite data indicate that the disturbance just south of Jamaica has become better organized this evening. Microwave and shortwave infrared images indicate that the center is now well defined, and deep convection has been persisting near and to the south of the center. Based on this data, the system now meets the criteria to be considered a tropical depression. The initial intensity remains 30 kt for this advisory. The depression is currently moving west-northwestward at 8 kt on the southern side of an Atlantic subtropical ridge. A continued west-northwest to northwest motion at about the same forward speed is expected during the next 24 to 36 hours, taking the system across the Cayman Islands and toward western Cuba. Around the time the depression is expected to be near western Cuba, the models show it accelerating northwestward as it moves in the faster flow between the ridge and Tropical Storm Gamma. This motion should bring the tropical cyclone into the southern Gulf of Mexico Tuesday night or early Wednesday. Later on, a notable slow down and a turn to the north is forecast to occur late in the week when the depression will likely be approaching the northern Gulf coast. This change in the forecast motion is a result of the ridge weakening and a trough approaching the cyclone from the west. The models are in relatively good agreement, which is surprising since they often diverge for weak systems, and the NHC track forecast lies near the middle of the guidance envelope. There is currently some northeasterly shear affecting the depression, but the models all show the shear lessening by tomorrow and remaining fairly light for the next few days. These improving upper-level wind conditions combined with a moist air mass and warm waters should allow for at least steady strengthening during the next few days. By late in the week, when the storm is forecast to approach the U.S. Gulf coast, there could be an increase in southerly or southwesterly shear, which could limit additional strengthening by that time. The NHC intensity forecast lies fairly close to the IVCN and HCCA consensus aids, and shows the depression becoming a hurricane near western Cuba with additional strengthening over the Gulf of Mexico. Users are reminded that the average 4- and 5-day NHC track forecast errors are about 160 to 200 miles at those time periods, respectively. Key Messages: 1. Tropical storm conditions are expected in the Cayman Islands beginning late Monday, and a Tropical Storm Warning is in effect. 2. Dangerous storm surge and hurricane conditions are possible in portions of western Cuba and the Isle of Youth by Tuesday afternoon, and a Hurricane Watch is in effect. 3. Heavy rainfall will affect portions of Hispaniola, Jamaica, the Cayman Islands, and western Cuba during the next few days and could lead to life-threatening flash floods and mudslides. 4. The system is forecast to approach the northern Gulf Coast late this week as a hurricane. While there is large uncertainty in the track and intensity forecasts at these time ranges, there is a risk of dangerous storm surge, wind, and rainfall hazards along the coast from Louisiana to the western Florida Panhandle. Residents in these areas should monitor the progress of the system and check for updates to the forecast during the week. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 17.0N 77.3W 30 KT 35 MPH 12H 05/1200Z 17.4N 78.3W 35 KT 40 MPH 24H 06/0000Z 18.3N 79.8W 40 KT 45 MPH 36H 06/1200Z 20.0N 81.9W 50 KT 60 MPH 48H 07/0000Z 22.2N 84.4W 65 KT 75 MPH 60H 07/1200Z 24.1N 87.0W 80 KT 90 MPH 72H 08/0000Z 25.4N 88.8W 85 KT 100 MPH 96H 09/0000Z 27.2N 90.4W 90 KT 105 MPH 120H 10/0000Z 30.0N 89.9W 75 KT 85 MPH...INLAND $$ Forecaster Cangialosi |