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First the link to this week's complete list as HTML and as PDF.
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Keellings & Hernández Ayala's claims from their abstract and conclusion are not upheld by their data. It is not only unsurprising but the whole point of one hundred year events that you only find them once in a period of only sixty years. Totally random events have to happen some time and some place. It is a quite common fallacy, mostly found in epidemiology, to pick that place and time after the event and conclude there to be something special about them. In the same vein it tells us nothing, that Hurricane Maria only came right at the end of the observation period, as it was this that triggered the whole study in the first place. Trying to estimate return periods is not an exact endeavour and there's no surprise that estimates from periods that do contain an event of the relevant size yield lower estimates than those that don't. Looking at figures 1 c & d Maria's are of course the highest data points but not truly exceptional even in those sixty years with six evenly distributed extreme, if slightly smaller, outliers.
There is a telling example of people's inability to understand rare events. After a catastrophic one-hundred-year-flood in Saxony the Malter flood containment dam was built in 1913. Sixty years later, when no other one-hundred-year-downpour had occurred, it was decided to fill up the basin, intentionally kept half empty, to near the top to make recreational water sports that much nicer. In 2002, when the next flood came more or less exactly one hundred years after the one before, the dam overflowed at once and the flood was as bad or worse than without a dam in the first place. Today the basin has been lowered again. Let's wait another fifty years or so and see how well people will remember then, or not.
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