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| #1144326 (Received by flhurricane at: 10:48 PM 18.Jul.2023) TCDAT5 Tropical Storm Don Discussion Number 20 NWS National Hurricane Center Miami FL AL052023 300 AM GMT Wed Jul 19 2023 Don`s convective structure continues to sputter along this evening, with only a small area of cold cloud tops below -50C centered just to the east of the low-level center. However, there has been some modest improvement of the low-level structure on microwave imagery, with some curved bands on storm`s east side. The latest subjective and objective Dvorak classifications remain around 35 kt, and that will remain the intensity for this advisory. While the ongoing convection is relatively meager, it is currently occuring within Don`s radius of maximum wind. High-resolution guidance (HAFS-A and HWRF) does show this convection persisting near the center, possibly helping to develop a smaller wind core over the next several days. Don is also expected to continue moving over gradually warmer waters to near 26 C in 24-36 hours as the mid-levels moisten and shear remains under 15 kt. Thus, some gradual intensification continues to be shown over the next couple of days, peaking the system at 45 kt in about 48 h. After that time, Don`s intensity is likely to be influenced by its future track, with a more westward motion taking Don toward warmer waters. However, the current NHC forecast track takes Don closer to the cold wake it generated over the weekend. In fact, the latest SHIPS guidance shows SSTs decreasing again after 48 h, and thus little additional intensification is shown after that time, which remains a bit under the consensus aids. By days 4-5, Don should be moving beyond the north wall of the Gulf Steam, likely losing its remaining convection and becoming post-tropical. Don appears to be slowing its forward motion tonight, with the latest estimated motion at 190/3 kt. This slowdown is likely in preparation for the system to turn southwestward and westward over the next 24-36 h as an amplified subtropical ridge grows poleward over Don. This ridge is then expected to continue sliding eastward and merge with another subtropical ridge just offshore of northwestern Africa, which should provide an avenue for Don to escape northward and then northeastward by the end of the forecast period. There was not a lot of changes with the track guidance this cycle, as the weaker ECMWF remains on the eastern side of the guidance, while the stronger HAFS and GFS remain on the western side. The NHC track forecast is quite similar to the prior one, favoring a slightly more eastward track given that Don is forecast to be on the weaker end of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 34.3N 39.0W 35 KT 40 MPH 12H 19/1200Z 33.8N 39.3W 35 KT 40 MPH 24H 20/0000Z 33.5N 40.5W 40 KT 45 MPH 36H 20/1200Z 33.8N 41.7W 40 KT 45 MPH 48H 21/0000Z 34.6N 43.5W 45 KT 50 MPH 60H 21/1200Z 35.6N 45.6W 45 KT 50 MPH 72H 22/0000Z 37.3N 47.7W 45 KT 50 MPH 96H 23/0000Z 42.1N 49.6W 45 KT 50 MPH 120H 24/0000Z 47.2N 44.6W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Papin |
