Quantifying changes of wind speed distributions in the historical record of Atlantic tropical cyclones

Abstract. Here we re-examine the official Atlantic basin tropical cyclone (hurricane) database HURDAT (1851–2008) and quantify differences between wind speed distributions in the early historical (1851–1943) record and more recent observations. Analyses were performed at three different geographical levels: for all six-hourly track segments of all Atlantic basin events, all segments of all events that crossed the US mainland, and US landfalling segments alone. At all three geographical levels of study, distributions of windspeeds over the last two, four and six decades display negligible dispersion or systematic change over time. On the other hand and relative to wind speed frequencies for subsequent years, the 1851–1943 record has a marked and statistically significant over-representation of wind speeds largely corresponding to Saffir-Simpson Categories 1 and 2 and under-representation of Categories 4 and 5 events; importantly, no single Category 5 event is recorded prior to 1924. The stability of the distribution of windspeeds at landfall over the last six decades, the dataset in which we can have most confidence, suggests that the differences in the earlier record are most likely explained by well-known measurement and observational deficiencies. Moreover by disaggregating the Power Dissipation Index (PDI), we demonstrate that the upward trend in Atlantic basin PDI since 1970s does not imply stronger and longer duration Category 5 windspeeds despite a warming climate. These results have implications for hurricane catastrophe loss modeling for the insurance industry and long-term trend analyses of the historical wind speed record, especially those related to the attribution of the role of Global Climate Change.