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| #1149281 (Received by flhurricane at: 5:06 PM 24.Aug.2023) TCDAT3 Tropical Storm Franklin Discussion Number 17 NWS National Hurricane Center Miami FL AL082023 500 PM AST Thu Aug 24 2023 Since the prior advisory, Franklin`s appearance has not changed appreciably, with deep convection continuing to pulse near and to the east of the low-level circulation center. The last few center fixes from the earlier Air Force Reserve Reconnaissance mission showed the tropical storm has continued to turn eastward, though some of this motion might also be a reflection of the center being dragged in the general direction of the persistent convective bursts. The initial intensity for this advisory remains at 50 kt, out of respect of the earlier aircraft data, and is also close to the latest UW-CIMSS ADT estimate. Another reconnaissance mission will be in the storm tonight to provide an updated assessment of Franklin. As mentioned above, Franklin is now moving east-northeastward, estimated at 060/6 kt. This relatively unusual motion for a tropical cyclone in late August at such low latitude is a byproduct of a large weakness still parked north of Franklin. This weakness is thanks in part to a longwave trough, allowing the storm`s motion to be more influenced by a mid-level anticyclone currently located to its south over the Caribbean Sea. After the next 24 hours or so, the ridging begins to build in more to the east of the storm, resulting in both a slowdown and sharp turn north or north-northwestward between 24 to 48 hours. From there, Franklin takes a much more climatological motion northward and then recurves north-northeastward as it is steered between the subtropical ridge to its west and a amplifying mid-latitude trough digging into the Great Lakes region by the end of the forecast period. While there remains some cross-track spread in the track guidance solutions as Franklin makes its turn northward, both the latest ECMWF and GFS solutions have closed the gap between their tracks, and the latest NHC track only needed minor adjustments compared to the prior cycle. As discussed this morning, Franklin is expected to slowly intensify for the next 24-36 h as moderate vertical wind shear is expected to be somewhat offset by warm 29-30 C sea-surface temperatures. After Franklin makes its turn northward, a cutoff low is expected to drop southwest of the storm, placing it in a more favorable upper-level difluent flow pattern. The guidance this cycle is showing a bit faster rate of intensification early on, so the intensity forecast was raised slightly from 48-72 h, still showing a peak intensity just shy of major hurricane intensity. This forecast is now in good agreement with the HCCA corrected consensus aid, but is lower than the more aggressive HAFS-A/B regional hurricane model forecasts. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 22.4N 68.9W 50 KT 60 MPH 12H 25/0600Z 22.6N 68.1W 55 KT 65 MPH 24H 25/1800Z 23.1N 67.0W 55 KT 65 MPH 36H 26/0600Z 23.5N 66.6W 60 KT 70 MPH 48H 26/1800Z 24.3N 66.5W 70 KT 80 MPH 60H 27/0600Z 25.6N 67.1W 80 KT 90 MPH 72H 27/1800Z 27.3N 67.7W 95 KT 110 MPH 96H 28/1800Z 31.0N 68.3W 95 KT 110 MPH 120H 29/1800Z 35.4N 66.5W 85 KT 100 MPH $$ Forecaster Papin |
