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| #1144600 (Received by flhurricane at: 10:48 PM 20.Jul.2023) TCDAT5 Tropical Storm Don Discussion Number 28 NWS National Hurricane Center Miami FL AL052023 300 AM GMT Fri Jul 21 2023 The band of convection noted on the eastern side of Don during the previous advisory has wrapped around to the western side of the tropical cyclone tonight. However, Don still is struggling to mix out the dry air that earlier disrupted its convective structure. ASCAT-C at 2339 UTC and ASCAT-B at 0026 UTC nicely captured Don`s circulation, and both had a peak wind retrieval of 40 kt, a bit higher than earlier. However, there have been no changes to the subjective Dvorak CI numbers from TAFB and SAB this cycle and so the initial intensity remains 45 kt for this advisory. Don continues to move west-northwestward at 290/8 kt. The storm is being steered by a strong low- to mid-level ridge that should gradually first shift northeastward and then eastward of the cyclone as a short-wave trough currently over the Great Lakes ejects eastward into the Canadian Maritimes over the next few days. This synoptic pattern should result in Don turning to the northwest and then north over the next 36-48 hours. Afterwards, Don should complete recurvature northeast into the higher latitudes as it opens up into a trough. The track guidance consensus has stabilized not too far off from the prior forecast track, and very few adjustments were needed to the official NHC track for this forecast cycle. Don`s structure appears quite healthy in the low-levels, per earlier 37 GHz microwave imagery which showed evidence of a closed cyan ring. However, the combination of dry mid-level air and marginal (24-25 C) sea surface temperatures appear to be keeping deep convection (below -50C) in check while it attempts to wrap around the center. These factors are likely to limit intensification, and little change in strength is forecast over the next 36 h or so. Weakening is then forecast to begin by 48 h as Don approaches the north wall of the Gulf Stream and encounters a more hostile upper-level flow pattern. Most of the global and regional-hurricane model guidance show Don ceasing to produce organized convection by 72 h, and the storm is forecast to become post-tropical at that time, followed by dissipation in 96 h. This forecast is in good agreement with the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 34.8N 44.7W 45 KT 50 MPH 12H 21/1200Z 35.4N 46.1W 45 KT 50 MPH 24H 22/0000Z 36.9N 48.1W 45 KT 50 MPH 36H 22/1200Z 38.8N 49.9W 45 KT 50 MPH 48H 23/0000Z 41.1N 50.9W 40 KT 45 MPH 60H 23/1200Z 43.6N 51.1W 35 KT 40 MPH 72H 24/0000Z 46.2N 49.6W 30 KT 35 MPH...POST-TROPICAL 96H 25/0000Z...DISSIPATED $$ Forecaster Papin |
