It allows for some semi-objective comparisons between events. From this perspective, Helene rainfall was not quite as extreme as the 2015 S. Carolina storm or Florence (2018), but a big difference is the heaviest rain fell in the complex terrain, so the flood response was different (and worse). 2/

plenty of caveats as always about the details of these calculations, as summarized in @cristiproist.bsky.socialbsky.app/profile/cris... For one thing, return period estimates in the SE haven't been updated to include recent storms, so the real "1000-year" value is likely much higher

CPcristiproist.bsky.socialSep 27, 2024 2:36pm

We're seeing news of 1 in a 1000 year rainfall events, and of rivers reaching record height from Helene For a while, something has worried me about estimates of flood and precipitation return levels in the South and Southeast US, and (for once) it's not climate change. 1/