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| #1013175 (Received by flhurricane at: 4:44 PM 21.Aug.2020) TCDAT4 Tropical Depression Fourteen Discussion Number 6 NWS National Hurricane Center Miami FL AL142020 500 PM EDT Fri Aug 21 2020 Since this morning's advisory, the low-level swirl on which the Air Force reconnaissance plane made its last fix has apparently become the new center of circulation of the depression. A little bit of deep convection has developed over this new center during the past few hours, but on the whole there is very little convective activity in the central region of the circulation. The strongest and most persistent convection is located within a band that extends across the Cayman Islands toward western Cuba. An ASCAT pass from this morning showed winds of 25-30 kt to the northeast of the new center, so 30 kt remains the initial intensity on this advisory. It is a bit of a mystery why the depression has struggled to develop much central convection, given a seemingly low-shear environment and warm waters. Since these conditions are expected to continue for the next few days, intensification is still indicated in the official forecast, although the rate of strengthening has been muted a bit while the system approaches the Yucatan Peninsula given its current structure. After the center moves over the Gulf of Mexico, many of the models still show the cyclone reaching hurricane intensity in about 3 days, including the intensity consensus, and that possibility is still shown in the NHC forecast. By day 4, the cyclone is likely to be blasted by 30-40 kt of southwesterly shear, which would lead to weakening while it approaches the northwestern Gulf coast. The official forecast has been reduced at that time, although it's noteworthy to mention that it still lies above all the guidance on day 4. Now that there is more confidence in the initial position, the new motion estimate is a little to the right from before, but still toward the northwest, or 325/11 kt. A deep-layer trough over the Gulf of Mexico is forecast to be shoved aside by the Atlantic subtropical ridge building westward over the next 2 days. Even with this pattern change, the cyclone is expected to move generally northwestward for the entire 5-day forecast period. However, there has been a notable westward bend in some of the track models, (particularly the GFS and ECMWF) from days 3-5, which is likely due those models having a weaker cyclone steered more by the low-level ridge at that time. Since the NHC intensity forecast is mirroring this particular model trend, the track forecast has been shifted westward from the previous prediction on days 4 and 5 toward the GFS and ECMWF solutions. The track forecast is still of rather low confidence, with the spread among the model guidance being larger than normal at every forecast time period. Key Messages: 1. Tropical Depression Fourteen is expected to strengthen over the northwestern Caribbean Sea through Saturday, and it could still be near hurricane strength when it reaches the east coast of the Yucatan Peninsula of Mexico late Saturday. A Hurricane Watch and a Tropical Storm Warning are in effect for portions of that region. 2. The system is expected to move into the south-central Gulf of Mexico as a tropical storm on Sunday. Although some strengthening is anticipated Sunday and Monday, weakening is forecast as the system approaches the northwestern Gulf coast on Tuesday. It is still too soon to know exactly the location and magnitude of impacts the system will produce along the central or northwestern Gulf Coast, and interests in that area should continue monitoring the progress of this system over the next few days. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 17.7N 84.3W 30 KT 35 MPH 12H 22/0600Z 18.6N 85.0W 35 KT 40 MPH 24H 22/1800Z 19.8N 85.9W 45 KT 50 MPH 36H 23/0600Z 21.2N 87.1W 55 KT 65 MPH...INLAND 48H 23/1800Z 22.9N 88.7W 55 KT 65 MPH...OVER WATER 60H 24/0600Z 24.6N 90.4W 60 KT 70 MPH 72H 24/1800Z 26.2N 92.2W 65 KT 75 MPH 96H 25/1800Z 28.5N 95.0W 50 KT 60 MPH 120H 26/1800Z 30.0N 97.5W 30 KT 35 MPH...INLAND $$ Forecaster Berg |
