Issued at 500 PM AST Wed Sep 24 2025
641 WTNT43 KNHC 242035 TCDAT3 Tropical Storm Humberto Discussion Number 1 NWS National Hurricane Center Miami FL AL082025 500 PM AST Wed Sep 24 2025 Satellite data indicates that Invest 93L over the central tropical Atlantic has now developed into Tropical Storm Humberto. Visible satellite imagery shows that throughout the day, the low-level center has become well-defined, with persistent and organized deep convection mainly located over the eastern side of the system. Subjective Dvorak intensity estimates from TAFB and SAB were both data-T/2.5 35 kt. DPRINT and DMINT Objective intensity estimates from UW-CIMSS range from 31 to 35 kt. Using these data, the initial intensity is set to 35 kt. The system is estimated to be moving west-northwestward at 300/13 kt, but this is of low confidence since the center has only recently formed. A west-northwestward to northwestward motion is anticipated through the next several days along the southwestern periphery of a mid-latitude ridge. Towards the end of the forecast period, an approaching trough moving offshore the east coast of the United States will erode the ridge and allow the system to turn more northward. However, there is quite a bit of uncertainty with the forward speed and cross-track spread of the system. This is increasingly apparent beyond day 3 as there are complex steering components with timing differences in the global models, including the approaching trough and potential binary interaction with Invest 94L. The NHC track forecast lies near the consensus aids given some of these uncertainties, and there is lower than normal confidence in the track forecast. The storm is within a favorable environment for strengthening with warm sea surface temperatures near 29C and moist mid-level RH values. The system will be dealing with some moderate westerly wind shear for the next day or so that will likely cause an asymmetric storm structure. EC and GFS SHIPS guidance depict the shear slightly weakening in the day 2 to 4 time frame, and with increasing divergence aloft, a slightly greater rate of strengthening is shown at that time. The latest NHC forecast follows these trends and lies near the consensus intensity aids. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 20.1N 54.9W 35 KT 40 MPH 12H 25/0600Z 20.9N 56.0W 40 KT 45 MPH 24H 25/1800Z 21.6N 57.0W 45 KT 50 MPH 36H 26/0600Z 22.0N 57.5W 50 KT 60 MPH 48H 26/1800Z 22.5N 58.2W 55 KT 65 MPH 60H 27/0600Z 22.9N 59.0W 60 KT 70 MPH 72H 27/1800Z 23.6N 60.6W 70 KT 80 MPH 96H 28/1800Z 26.0N 64.3W 90 KT 105 MPH 120H 29/1800Z 29.1N 67.1W 95 KT 110 MPH $$ Forecaster Kelly
