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| #1144662 (Received by flhurricane at: 10:57 AM 21.Jul.2023) TCDAT5 Tropical Storm Don Discussion Number 30 NWS National Hurricane Center Miami FL AL052023 1100 AM AST Fri Jul 21 2023 Shortly after the release of the previous advisory convection nearly wrapped completely around the center of Don. Since the time, the convection has become somewhat more fragmented, but there is still a well-defined curved band that wraps about three-quarters of the way around Don`s center. Subjective Dvorak T-numbers from SAB and TAFB are a unanimous T3.0 or 45 kt, so the initial intensity remains 45 kt for this advisory. A recently arriving scatterometer overpass missed the core of the cyclone so there is no information on the system`s strength from that data source this morning. The initial motion estimate is still west-northwestward or 300 degrees at 9 kt. A low- to mid-level ridge to the north-northeast of the cyclone is forecast to shift eastward during the next 24 to 36 hours causing Don to turn northwestward, and then northward during the next day or two. After that time, Don is expected to turn northeastward within low- to mid-level southwesterly flow between the ridge and a broad trough over eastern Canada and the northeastern United States. The dynamical models are tightly clustered and little overall change was made to the previous NHC track forecast. Don remains over marginally warm sea surface temperatures and within a relatively dry mid-level environment so little overall change in strength is predicted during the next 12 to 24 hours. The system is forecast to pass over the slightly warm waters of the Gulf stream on Saturday, but this is not likely to result in a significant change in strength. By Sunday morning, Don will have moved north of the Gulf stream and over much colder SSTs. This should result in weakening and the system`s transition into a post-tropical cyclone. Dissipation is predicted by the global models in a little more than 3 days, and the official forecast follows suit. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 35.8N 46.5W 45 KT 50 MPH 12H 22/0000Z 36.9N 48.0W 45 KT 50 MPH 24H 22/1200Z 38.8N 49.9W 45 KT 50 MPH 36H 23/0000Z 41.1N 50.9W 45 KT 50 MPH 48H 23/1200Z 43.7N 50.6W 40 KT 45 MPH 60H 24/0000Z 46.1N 49.1W 35 KT 40 MPH...POST-TROPICAL 72H 24/1200Z 48.4N 45.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 25/1200Z...DISSIPATED $$ Forecaster Brown |
