Issued at 1100 AM AST Sun Sep 28 2025
471 WTNT43 KNHC 281437 TCDAT3 Hurricane Humberto Discussion Number 16 NWS National Hurricane Center Miami FL AL082025 1100 AM AST Sun Sep 28 2025 Humberto has weakened slightly, likely the result of an ongoing eyewall replacement cycle, but it remains a powerful hurricane. The initial intensity of 130 kt is based primarily on a blend of Final-T and CI Dvorak values from TAFB. That value is on the high end of the various objective estimates, but the 1210 UTC UW-CIMSS DPRINT Vmax value was also 130 kt. For the next day or two, Humberto's intensity will likely be determined largely by internal dynamics like additional eyewall replacement cycles, and by how large of an eye it develops. GPM microwave data from earlier this morning showed the presence of a very large outer ring of deep convection around Humberto's center. If that larger ring ultimately replaces Humberto's eyewall, it could result in the hurricane having a lower intensity in the short term than currently forecast, but a rapidly larger extent of hurricane-force winds. Consequently, the main concern for Humberto going forward is not how strong it will be, but how large. In addition to the expected expansion of Humberto's hurricane-force inner core, the tropical-storm-force wind radii are also expected to expand quickly in the next few days. As a result of this, even though the core of Humberto is forecast to move west and then north of Bermuda, tropical-storm-force impacts appear increasingly likely and tropical storm watches could be required there later today. Humberto is also expected to produce swells that affect most of the western Atlantic, with dangerous surf conditions starting along the U.S. East Coast on Monday. Humberto's initial motion hasn't changed, and the track forecast reasoning is very similar to previous forecasts. Humberto should move around the southwest periphery of the subtropical ridge for the next couple of days, moving west of Bermuda on Tuesday. The hurricane should then accelerate east-northeastward as it becomes post-tropical. Humberto's winds should expand further as its intensity gradually decreases through the middle of the week, but it is forecast to remain a very powerful hurricane-force low, even after it becomes post-tropical. KEY MESSAGES: 1. There is an increasing risk of tropical-storm-force winds affecting Bermuda by late Tuesday. Interests there should monitor the progress of Humberto and watches could be issued later today. 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 the U.S. East Coast on Monday. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 24.6N 64.3W 130 KT 150 MPH 12H 29/0000Z 25.7N 65.7W 125 KT 145 MPH 24H 29/1200Z 27.3N 67.2W 120 KT 140 MPH 36H 30/0000Z 29.3N 68.4W 110 KT 125 MPH 48H 30/1200Z 31.6N 69.0W 100 KT 115 MPH 60H 01/0000Z 33.7N 68.3W 95 KT 110 MPH 72H 01/1200Z 35.6N 65.0W 90 KT 105 MPH 96H 02/1200Z 39.7N 51.0W 80 KT 90 MPH...POST-TROP/EXTRATROP 120H 03/1200Z...DISSIPATED $$ Forecaster D. Zelinsky
NHC Atlantic
