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| #1246526 (Received by flhurricane at: 10:57 AM 29.Sep.2025) TCDAT3 Hurricane Humberto Discussion Number 20 NWS National Hurricane Center Miami FL AL082025 1100 AM AST Mon Sep 29 2025 Air Force Reserve Hurricane Hunter aircraft found Humberto has strengthened this morning. The aircraft depicted that the system has completed an eyewall replacement cycle, with the outer eyewall as depicted on earlier microwave imagery now dominant, and the old inner eyewall has collapsed. The aircraft however did depict that the eyewall is open on the southwest side which is likely due to the impacts of increasing wind shear. Maximum flight level winds in the northeast quadrant were 138 kt, which supported the increased intensity to 125 kt at the intermediate advisory. Using the latest hurricane hunter and scatterometer wind data, the wind radii have been slightly adjusted and the intensity is held at 125 kt for this advisory. Humberto is moving northwestward at an estimated motion of 325/ 11 kt, along the southwestern periphery of a mid-level subtropical ridge. A gradual turn to the north then northeast over the next day or so is anticipated as the system rounds the western periphery of the ridge, and the NHC forecast has been shifted slightly to the left closer to the consensus aids in the short term. The system will then begin to move northeast to east-northeastward as the system is picked up by a trough moving into the north Atlantic. The NHC forecast is similar to the previous through the end of the forecast period, with a slight nudge towards the latest consensus aids. Some fluctuations in intensity are possible over the next 12 h or so. Thereafter, increasing wind shear and cooling sea surface temperatures should induce a weakening trend. The wind shear will also cause Humberto become quite asymmetric with most of the convection displaced to the eastern side of the circulation. In about 60 h, global models depict that the system should merge with the previously mentioned trough digging across the north Atlantic and develop frontal features. As the system becomes extratropical across the north Atlantic, the wind field is anticipated to grow in size. The latest NHC intensity forecast lies on the higher end of the guidance envelope given the latest increase in intensity, and then shows weakening throughout the period. By 96h, the system is expected to dissipate and merge within the larger trough. Along the forecast track, Humberto is expected to move to the west and north of Bermuda, although there is a possibility of tropical-storm-force winds occuring over the island late Tuesday and Wednesday within outer rainbands. 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 29/1500Z 28.0N 67.6W 125 KT 145 MPH 12H 30/0000Z 29.6N 68.5W 115 KT 130 MPH 24H 30/1200Z 32.1N 69.0W 105 KT 120 MPH 36H 01/0000Z 34.4N 67.9W 95 KT 110 MPH 48H 01/1200Z 36.1N 64.5W 90 KT 105 MPH 60H 02/0000Z 37.4N 58.5W 80 KT 90 MPH...POST-TROP/EXTRATROP 72H 02/1200Z 40.6N 49.0W 75 KT 85 MPH...POST-TROP/EXTRATROP 96H 03/1200Z...DISSIPATED $$ Forecaster Kelly |
