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| #1105904 (Received by flhurricane at: 4:36 PM 05.Sep.2022) TCDAT5 Hurricane Danielle Discussion Number 19 NWS National Hurricane Center Miami FL AL052022 900 PM GMT Mon Sep 05 2022 After a large degradation in Danielle`s appearance earlier this afternoon, the hurricane appears to be holding more steady now with colder cloud tops wrapping further around its center than were noted 6 hours ago. Dvorak-based intensity estimates still support an intensity near 75 kt. The hurricane has moved a little faster north-northeastward than anticipated during the last few hours, with an initial motion estimate of 030/kt. A significant adjustment was made to the track forecast at days 4 and 5, at which time Danielle is forecast to be an extratropical cyclone. For the first 3 days of the forecast period, Danielle is still forecast to move generally northeastward in the mid-latitude flow. After that, it looks like Danielle could occlude and "cut-off" from that steering flow, which may cause it to turn abruptly northward and then southeastward at days 4-5. This scenario has been consistently forecast for a few model cycles of the GFS and other global models, so large changes were made to the NHC track forecast to bring it closer to the model consensus. Other than a slight adjustment northward and faster, no important changes were made to the NHC track forecast for the first 72 h. Given the uncertainty at the extended portion of the forecast, it should be noted that confidence in the track forecast is substantially higher for the first 72 h than the later hours. It is worth noting that Danielle is forecast to be post-tropical by 96 h, so users should not focus on the exact track of the cyclone since the largest impacts could be felt far from its center. Danielle should slowly weaken during the next few days as it moves over marginally cool water, but most dynamical guidance suggests it will still maintain its tropical characteristics for at least a couple more days. Around day 3, SHIPS diagnostics indicate the waters below the cyclone will be less than 20 deg C, and it will likely complete its extratropical transition around that time. The NHC forecast follows accordingly, but it should be noted this suggests a slightly later completion to the transition than previously forecast. The NHC intensity forecast is near the middle of the relatively low-spread intensity guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 41.1N 43.2W 75 KT 85 MPH 12H 06/0600Z 41.9N 42.2W 70 KT 80 MPH 24H 06/1800Z 42.6N 40.4W 70 KT 80 MPH 36H 07/0600Z 43.4N 38.1W 65 KT 75 MPH 48H 07/1800Z 44.6N 35.3W 65 KT 75 MPH 60H 08/0600Z 46.2N 32.4W 60 KT 70 MPH 72H 08/1800Z 48.2N 29.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 09/1800Z 50.0N 29.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 10/1800Z 47.5N 25.5W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster D. Zelinsky |
