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| #1149791 (Received by flhurricane at: 5:00 AM 28.Aug.2023) TCDAT3 Hurricane Franklin Discussion Number 31 NWS National Hurricane Center Miami FL AL082023 500 AM EDT Mon Aug 28 2023 Franklin has continued to improve in organization during the overnight hours. The eye noted in the previous advisory has occasionally cleared out on infrared satellite imagery, with the cold eyewall temperatures surrounding it cooling to between -65 to -75 C in a thick region around the center. Subjective Dvorak classifications were both T5.5/102 kt from TAFB and SAB, while UW-CIMSS ADT estimates are now as high as T5.7/107 kt. The initial intensity was raised to 100 kt at 06 UTC, and that will remain the intensity at 09 UTC. While this may be slightly conservative, earlier aircraft data showed that the maximum winds were lagging the satellite presentation and minimum pressure of the hurricane. This intensity still makes Franklin the first major hurricane of the 2023 Atlantic hurricane season. Another Air Force Reconnaissance mission will be in the hurricane this morning to provide an updated assessment of the storm. The hurricane continues to make a gradual turn northward, with the latest motion estimate still north-northwest at 335/7 kt. Over the next 48 hours the hurricane should continue to turn northward and then north-eastward as it rounds the western periphery of a subtropical ridge, and very little change was made to the NHC track over this time period. After 48 hours, there continues to be significant spread, especially in the along-track direction, related to how much a mid-latitude trough ejecting out of Canada is able to capture the hurricane. The big change this forecast cycle is that the ECMWF has come on board showing a trough capture, though it still remains slower than the majority of the guidance suite. The latest NHC track forecast has thus been adjusted a bit north and is quite a bit faster after 48 hours, but is not quite as fast as the TCVN and HCCA consensus aids over this period. Some additional intensification is anticipated today, as Franklin remains in a low shear environment and is over warm 29-30 C sea-surface temperatures. The latest intensity forecast still peaks Franklin as a Category 4 (115-kt) major hurricane. However, inner-core changes, such as eyewall replacement cycles, could occur at any time, making it somewhat tricky to pinpoint exactly when Franklin will reach peak intensity. After 24 hours, the broadening wind field and relatively slow storm motion could make the hurricane prone to some local upwelling. In addition, some northwesterly shear may also begin to affect the storm. Toward the end of the forecast period, more dramatic weakening is possible as the storm gets swept up in the mid-latitudes. The latest forecast shows the storm becoming a post-tropical extratropical cyclone in 120 h, though this could occur sooner than forecasted if the faster solutions, like the GFS, pan out. The current forecast shows the core of Franklin passing west and north of Bermuda in about 60 h, but a tropical storm watch may still become necessary later today as its expanding 34-kt wind field to the southeast does get close to the island after 48 hours. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 27.2N 70.8W 100 KT 115 MPH 12H 28/1800Z 28.3N 71.1W 110 KT 125 MPH 24H 29/0600Z 29.8N 71.0W 115 KT 130 MPH 36H 29/1800Z 31.6N 70.2W 105 KT 120 MPH 48H 30/0600Z 33.2N 68.6W 95 KT 110 MPH 60H 30/1800Z 35.0N 65.7W 90 KT 105 MPH 72H 31/0600Z 37.0N 62.0W 85 KT 100 MPH 96H 01/0600Z 42.0N 53.0W 75 KT 85 MPH 120H 02/0600Z 48.0N 44.0W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Papin |
