Cooperative Institute for Research in the Atmosphere

How Strong are the Strongest Wind Gusts within Tropical Cyclones?

The most intense tropical cyclones are characterized by maximum 1-minute mean surface (10-meter) wind speeds of 70-90 ms-1. Dropsondes within the boundary layer occasionally sample gusts (representative of timescales of a few seconds) exceeding 90 ms-1 and (more rarely) 100 ms-1. Such extreme wind gusts are found in nearly every category-5 tropical cyclone, but because of irregular and sparse sampling, it is unclear how frequent these gusts are, or whether they actually represent the upper-limit of wind speed in TCs. In this talk, I will present a large-eddy simulation of a realistic category-5 TC, and show that there are nearly always gusts exceeding 120 ms-1 somewhere within the eyewall. I will then show that realistic sampling with “virtual” dropsondes yields wind gust distributions similar to what has been observed, and that gusts exceeding 110 ms-1 are very rarely sampled. Based on the observed dropsondes and the simulation, I conclude that it is likely that real category-5 TCs are characterized by peak gusts of 120-140 ms-1.