Trends and ENSO-related variability in Atlantic tropical cyclone intensity and intensification

Michael K. Tippett, Suzana J. Camargo

This study examined trends and ENSO-related variability in Atlantic tropical cyclone intensity, focusing on 24-h intensification, lifetime maximum intensity (LMI), and rapid intensification (RI) in best-track data during the period 1982–2024.  Previous studies considered trends and ENSO influences separately, reporting upward trends in intensity and more cases of RI during La Niña conditions.  Here we extended and built upon prior work by including data through 2024, assessing the impact of ENSO on LMI and 24-h intensification, and analyzing a new storm metric called lifetime maximum 24-h intensification (LM24I).  The statistical methods employed here improve upon previous ones by better assessing uncertainty and statistical significance, simultaneously estimating trends and ENSO-related variability, and addressing problems arising from the 5-kt discretization of best-track intensity data.  Quantile and logistic regression were employed extensively. The main findings include the following: Prior estimates of intensification trends were overconfident, and including recent data reduces prior estimates of trends in intensification, RI frequency, and LMI.  The distribution of LM24I shows significant upward trends of 3–5 kt per decade in its top quantiles and broad increases of 2–5 kt per degree of Niño-3.4 cooling. During La Niña conditions, the frequencies of RI events and RI storms increase, and the distributions of 24-h intensification and LMI show previously unreported broad and significant increases.  Directions for future research include applying the same approaches to other intensity metrics, basins, and model output, and leveraging ENSO predictability for seasonal intensity prediction.