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| #1246499 (Received by flhurricane at: 5:03 AM 29.Sep.2025) TCDAT3 Hurricane Humberto Discussion Number 19 NWS National Hurricane Center Miami FL AL082025 500 AM AST Mon Sep 29 2025 Humberto has gone through some inner-core structural changes. Earlier aircraft data indicated that the hurricane had a double eyewall structure, but a 29/0546 UTC AMSR2 microwave pass indicates that the inner eyewall is starting to get overtaken by the outer eyewall. Given the the apparent continued weakening of the inner eyewall as inferred from GOES-19 imagery since the time of the microwave pass, Humberto`s maximum sustained winds are probably near the lower end of the recent objective and subjective estimates, so the initial intensity is nudged downward slightly to 115 kt. Another Air Force plane will be in Humberto in a few hours to better assess the intensity. Humberto is still moving northwestward, or 320 degrees at 12 kt in the flow on the south-southwest side of a subtropical high. The major hurricane is expected to gradually turn to the north over the next 24 hours as the high shifts to the east and weakens. After that, a trough is expected to amplify over the north Atlantic, and that should cause Humberto to turn sharply and accelerate east-northeastward Tuesday night and Wednesday. The NHC forecast is similar to the previous one through 24 h, but then has been shifted slightly to the northwest, or left, of the previous forecast after that time, close to the latest model consensus. Confidence in the track forecast is high through 48 h. While there is high confidence that the core of Humberto will miss Bermuda, there is a possibility of tropical-storm-force winds occurring there late Tuesday and Wednesday in Humberto`s outer bands. The intensity of Humberto will likely fluctuate over the next 12 h or so, but gradual weakening is expected after that due to increasing shear and decreasing SSTs. Extratropical transition is expected to be complete in 60-72 hours when the system is forecast to merge with the aforementioned mid- to upper-level trough and develop frontal features. The NHC intensity forecast is between the middle and higher end of the guidance envelope. The hurricane is expected to grow in size as it gains latitude during the next few days, which will result in a large area of rough seas. See Key Messages below for more information. KEY MESSAGES: 1. Tropical-storm-force winds could begin to affect Bermuda by late Tuesday, and a tropical storm watch is in effect for the island. Interests there should continue to monitor the progress of Humberto. 2. Dangerous marine conditions, including high surf and life-threatening rip currents, are affecting beaches of the northern Caribbean, Bahamas, and Bermuda. The dangerous surf conditions are expected to begin affecting much of the east coast of the U.S. today. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 27.2N 66.9W 115 KT 130 MPH 12H 29/1800Z 28.6N 68.0W 115 KT 130 MPH 24H 30/0600Z 30.9N 68.9W 105 KT 120 MPH 36H 30/1800Z 33.3N 68.7W 95 KT 110 MPH 48H 01/0600Z 35.4N 66.7W 90 KT 105 MPH 60H 01/1800Z 36.9N 61.7W 85 KT 100 MPH 72H 02/0600Z 39.0N 54.5W 80 KT 90 MPH...POST-TROP/EXTRATROP 96H 03/0600Z...DISSIPATED $$ Forecaster Hagen |
