The growing inadequacy of an open-ended Saffir–Simpson hurricane wind scale in a warming world

Abstract

Global warming increases available sensible and latent heat energy, increasing the thermodynamic potential wind intensity of tropical cyclones (TCs). Supported by theory, observations, and modeling, this causes a shift in mean TC intensity, which tends to manifest most clearly at the greatest intensities. The Saffir–Simpson scale for categorizing damage based on the wind intensity of TCs was introduced in the early 1970s and remains the most commonly used metric for public communication of the level of wind hazard that a TC poses. Because the scale is open-ended and does not extend beyond category 5 (70 m/s windspeed or greater), the level of wind hazard conveyed by the scale remains constant regardless of how far the intensity extends beyond 70 m/s. This may be considered a weakness of the scale, particularly considering that the destructive potential of the wind increases exponentially. Here, we consider how this weakness becomes amplified in a warming world by elucidating the past and future increases of peak wind speeds in the most intense TCs. A simple extrapolation of the Saffir–Simpson scale is used to define a hypothetical category 6, and we describe the frequency of TCs, both past and projected under global warming, that would fall under this category. We find that a number of recent storms have already achieved this hypothetical category 6 intensity and based on multiple independent lines of evidence examining the highest simulated and potential peak wind speeds, more such storms are projected as the climate continues to warm.

A storyline-based approach towards changing typhoon intensities over the Pearl River Delta under future conditions using Pseudo-Global Warming

“…This is especially the case for Mujigae, Hagupit, and Usagi, with the former two being the most intense typhoons out of the seven inspected cases, purely based on maximum wind speed. Our results further demonstrate large based on wind speed in the past (Jordan and Clayson, 2008;Bloemendaal et al, 2021;Walker et al, 2018;Wehner and Kossin, 2024;Kantha, 2006) Based on our findings, we recommend a more in-depth re-evaluation of typhoon intensity under multiple sophisticated approaches of determining typhoon intensity, also considering their respective damage potential that not only depends on wind speed.…”

“…Since there exist indications that the traditional Saffir-Simpson Hurricane Wind Scale may be insufficient to determine the potential impact of tropical cyclones (Kantha, 2006;Bloemendaal et al, 2021;Wehner and Kossin, 2024), we selected the IKE to better capture the true damage potential of the inspected typhoons.…”

Damage to tropical forests caused by cyclones is driven by wind speed but mediated by topographical exposure and tree characteristics

“…6 g cm −3 ), for Category 1 tropical cyclones (MSW = 33-43 m s −1 ), <15% of trees could be snapped or uprooted, while for MSW of 70 m s −1 (Category 5 tropical cyclones threshold value) ~25%-65% of trees could be snapped or uprooted, depending on topographical exposure to wind. Based on our models, these proportions can reach ~45%-90% for MSW of 86 m s −1 (the proposed 'Category 6' tropical cyclone threshold value suggested byWehner & Kossin, 2024). Our model indicates a sharp increase in damage when wind speeds reach Category 3 intensity or higher (≥50 m s −1 ); similar patterns were found using a remote sensing vegetation index in the southwest Pacific F I G U R E 4 Predicted proportion of damaged (snapped or uprooted) trees by Model 1 (N = 74 plots), (a) median prediction (lines) and 90%-highest posterior density interval along the extended range of observed maximum sustained wind speed (MSW) for three different values of maximum topographical exposure to wind (EXP, 0.0, 0.3 and 0.6), (b-g) predicted posterior distribution of the proportion of damaged trees for different combinations of MSW…”

“…The scale is a function of the maximum sustained wind speed (MSW) generated by tropical cyclones and classifies them from Category 1 (MSW 33-42 m s −1 ) to Category 5 (MSW ≥70 m s −1 ). Given the increasing intensity of tropical cyclones, as exemplified by super-typhoon Haiyan (2013), an additional 'Category 6' has been proposed for tropical cyclones with MSW ≥80 m s −1 (Lin et al, 2014) and more recently with MSW ≥86 m s −1 (Wehner & Kossin, 2024). Higher MSW should increase mechanical wind loads on trees and result in higher proportions of trees that are either snapped (bole failure) or uprooted (root failure).…”

Human Civilization will Collapse (High Confidence): A Compendium of Relevant Biophysical, Political, Economic, Military, Health, and Psychological Information on Climate Change

“…We investigate considering the extension to a 6th category of the Saffir-Simpson hurricane wind scale to communicate that climate change has caused the winds of the most intense TCs to become significantly higher. (Wehner & Kossin, 2024) A 6th category would make it easier to identify the most extreme tropical cyclones, but there is worry that it might lead to less fear, and thus less evasive action, when a category 5 storm is predicted. A more serious criticism of the Saffir-Simpson scale is that it takes only wind speed into consideration, while most deaths are water related (e.g., via storm surge and flooding).…”