Issued at 500 AM AST Sun Sep 28 2025
046 WTNT43 KNHC 280859 TCDAT3 Hurricane Humberto Discussion Number 15 NWS National Hurricane Center Miami FL AL082025 500 AM AST Sun Sep 28 2025 Humberto continues to display a clear, circular eye about 10-15 miles in diameter. Although the eye temperatures are still fairly warm around 15C, the area of cloud tops colder then -70C has shrunk a bit in the southwest quadrant, and data-T numbers have continuously been lower than 7.0 for about 8 hours now. The latest subjective CI numbers range from 127-140 kt, and the latest objective intensity estimates range from 125-135 kt. Based on the above analyses and data, the initial intensity is nudged down to 135 kt. The initial motion estimate is west-northwestward, or 300 degrees at 11 kt. Over the next couple of days, Humberto will round the southwestern periphery of a mid-tropospheric subtropical ridge located northeast of the cyclone. Humberto will turn northward by early Tuesday in between the ridge and Tropical Depression Nine, which should be located to the west-southwest of Humberto. By Tuesday night, Humberto is forecast to turn north-northeastward while the aforementioned ridge weakens and shifts eastward. Humberto should turn quickly toward the northeast to east-northeast by mid-week in response to a large, amplifying upper-level trough moving out of the Canadian Maritimes and into the northwestern Atlantic waters. There remains quite a bit of along-track spread at days 4 and 5. The new NHC forecast is slightly faster toward the northwest through 48 h, then lies to the northwest, or left of, the previous official forecast at 60-72 when it makes its closest approach to Bermuda. In other words, the new forecast shows the center passing a bit farther from Bermuda, however, Bermuda still has roughly a 50 percent chance of getting tropical-storm-force winds, most likely on Tuesday night and Wednesday. There have been no recent microwave passes over Humberto in the last 6 h, but infrared imagery suggests there could be a partial outer ring trying to become more dominant. SHIPS predictors and the UW-CIMSS Microwave-based Probability of Eyewall Replace Cycle (M-PERC) guidance indicate a high likelihood of an eyewall replacement cycle commencing within the next 12 h. Otherwise, environmental conditions are pretty favorable for the next 12 h, so the forecast will show Humberto maintaining its current intensity for 12 h despite the potential for fluctuations. Thereafter, all of the intensity guidance points toward gradual weakening as there is potential for gradually increasing vertical wind shear during the 36 to 60 hour time frame. By hour 72, Humberto should encounter significantly stronger upper-level westerly flow and begin the process of extratropical transition. Extratropical transition should be complete around 96 h, after Humberto crosses the 26 degree C sea-surface temperature isotherm, as all global models show a warm front extending northeastward from Humberto by that time. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 23.9N 63.3W 135 KT 155 MPH 12H 28/1800Z 24.9N 64.7W 135 KT 155 MPH 24H 29/0600Z 26.4N 66.4W 130 KT 150 MPH 36H 29/1800Z 28.3N 67.8W 120 KT 140 MPH 48H 30/0600Z 30.3N 68.7W 115 KT 130 MPH 60H 30/1800Z 32.5N 68.7W 105 KT 120 MPH 72H 01/0600Z 34.5N 67.1W 95 KT 110 MPH 96H 02/0600Z 38.2N 56.0W 85 KT 100 MPH...POST-TROP/EXTRATROP 120H 03/0600Z 46.4N 37.5W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Hagen
NHC Atlantic
