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| #1143619 (Received by flhurricane at: 11:03 AM 14.Jul.2023) TCDAT5 Subtropical Storm Don Discussion Number 2 NWS National Hurricane Center Miami FL AL052023 1100 AM AST Fri Jul 14 2023 Don`s deep convection has been waning in intensity since the overnight hours, with most of the activity located in broken bands to the north and east of the center of circulation. The cyclone remains subtropical, given that it is embedded within a deep-layer trough and has a relatively large radius of maximum winds. A just-received ASCAT pass over Don shows a swath of 35-40 kt winds to the east of the center, so the initial intensity is therefore lowered to 40 kt. Don`s recent motion has been north-northwestward, or 340/6 kt, with the cyclone surrounded by a pair of strong mid-level ridges to its east and north, and a broad trough over the western Atlantic. The ridge to the east will be the main steering influence, and that feature is expected to migrate westward across the Atlantic during the next several days. Don is forecast to move slowly around the northern side of the ridge, turning northward, eastward, and then southeastward over the next 5 days. In spite of the somewhat complicated mid-latitude pattern, the track models are in fairly good agreement for much of the forecast period. The new NHC track forecast is nudged northward during the 2- to 4-day part of the forecast toward the consensus aids but otherwise is very similar to the forecast from earlier this morning. Subsiding dry air on the back side of the trough is getting entrained into Don`s circulation, and the storm is over waters of 25-26 degrees Celsius, heading towards waters as cold as 23 degrees in about 3 days. Although the trough may be able to continue to supply some baroclinic energy to Don, the cyclone`s maximum winds are likely to gradually diminish over the next few days given the less favorable thermodynamic environment. There is a chance that Don could lose enough convective organization and become a post-tropical cyclone at some point during the next few days. However, by days 4 and 5, Don will be heading back southward toward relatively warmer waters, and a new mid-latitude shortwave trough may provide a boost to the system`s organization and strength. As a result, the NHC intensity forecast shows possible restrengthening at the end of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 33.7N 47.3W 40 KT 45 MPH 12H 15/0000Z 34.5N 47.5W 40 KT 45 MPH 24H 15/1200Z 36.0N 47.8W 40 KT 45 MPH 36H 16/0000Z 37.4N 48.1W 35 KT 40 MPH 48H 16/1200Z 38.5N 47.7W 35 KT 40 MPH 60H 17/0000Z 39.0N 46.2W 35 KT 40 MPH 72H 17/1200Z 38.6N 43.9W 35 KT 40 MPH 96H 18/1200Z 35.7N 40.0W 35 KT 40 MPH 120H 19/1200Z 33.7N 38.6W 40 KT 45 MPH $$ Forecaster Berg |
