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| #1143572 (Received by flhurricane at: 4:45 AM 14.Jul.2023) TCDAT5 Subtropical Storm Don Discussion Number 1 NWS National Hurricane Center Miami FL AL052023 500 AM AST Fri Jul 14 2023 The area of low pressure that NHC has been monitoring roughly midway between Bermuda and the Azores has become Subtropical Storm Don. The storm is assessed as subtropical because it is embedded within an upper-level trough and has a relatively large radius of maximum wind. Several hours ago, a well-defined center of circulation developed and deep convection has remained sufficiently organized, especially in bands to the east of the center. A pair of partial ASCAT passes from around 00Z showed peak winds around 45 kt, and that is the initial intensity set for this advisory. Don has been moving slowly northward at about 5 kt during the past 6 to 12 hours, and a continued slow northward or north-northwestward motion is expected during the next couple of days as a building ridge over the central Atlantic prevents it from accelerating poleward. That ridge is expected to weaken on Sunday while another ridge builds to the southeast of Don and a trough amplifies over the northeastern Atlantic. This pattern change should cause Don to turn eastward on Sunday and then southeastward early next week. The NHC track forecast lies near the middle of the guidance envelope, in best agreement with the various consensus aids. The storm is likely near its peak intensity already. Dry air is wrapping in on the south and west sides of the circulation and that stable air is expected to continue to entrain into the storm during the next several days. In addition, sea surface temperatures are expected to decrease along the forecast track during the next 2 or 3 days. Although the environment is not conducive for strengthening, it is also not hostile enough to cause significant weakening. Therefore, the NHC official forecast shows a gradual decay in Don’s strength. The environment looks more conducive by the end of the period, and some strengthening is possible by then if the storm survives that long. The NHC intensity forecast follows the theme of the models, which are tightly clustered. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 32.9N 46.8W 45 KT 50 MPH 12H 14/1800Z 33.5N 47.0W 45 KT 50 MPH 24H 15/0600Z 34.9N 47.3W 45 KT 50 MPH 36H 15/1800Z 36.4N 47.8W 45 KT 50 MPH 48H 16/0600Z 37.6N 47.8W 40 KT 45 MPH 60H 16/1800Z 38.4N 47.1W 40 KT 45 MPH 72H 17/0600Z 38.5N 44.9W 35 KT 40 MPH 96H 18/0600Z 35.9N 40.7W 35 KT 40 MPH 120H 19/0600Z 33.4N 38.5W 40 KT 45 MPH $$ Forecaster Cangialosi |
