Hints of a derecho-climate change link, ten years after 2012 storm – The Washington Post

by | Jun 29, 2022 | Climate Change

Placeholder while article actions loadA decade ago, “derecho” — the term used to describe a fast-moving, extensive, enduring and violent complex of thunderstorms — was launched into the national spotlight when destructive storms swept from the Midwest to the Mid-Atlantic, cutting power to millions and claiming 22 lives.The violence of that storm event — which coincided with one of the hottest June days on record — raised questions at the time about the role of human-caused climate change. They were questions that, at the time, the research community was not equipped to answer.Since that infamous storm on June 29, 2012, a number of extreme heat-driven derechos have followed in its footsteps, breaking an array of records while leaving wide swaths of damage from Colorado to Canada.In just the past six and a half months, two of the most destructive derechos on record have occurred. Both events blasted sections of the Midwest; the first on Dec. 15, 2021, and the second on May 12 of this year. Both events occurred on days with record-setting heat.Meteorologists remember the June 2012 Mid-Atlantic derechoThe record-breaking temperatures associated with these recent events is yet again prompting questions about whether rising temperatures from human-caused climate change is increasing derecho destructiveness and, more troubling, might portend even more extreme derechos in the future. As these storm complexes can produce wind damage comparable to hurricanes, cost billions of dollars and leave people without power for weeks, as the Iowa derecho did in 2020, the stakes are high.AdvertisementArmed with 10 years of severe weather and climate change research since the 2012 derecho, scientists now say rising temperatures could well increase the fuel for these violent storms — making them stronger, more extensive and longer-lived — while shifting when and where they occur.In a warming word, “given the right ingredients, I think it’s reasonable to make the argument that derechos could be more intense and could be larger or more widespread,” said Jeff Trapp, head of the atmospheric sciences department at the University of Illinois, who studies severe thunderstorms.The derecho-extreme heat connectionAmid rising temperatures in recent years, derechos and other severe thunderstorm events have produced an increasing number of “significant” wind gusts — which the National Weather Service defines as 75 mph or higher.AdvertisementAll four of the top derechos, based on the number of reports of these significant gusts, have occurred since June 2020; all of the top nine derechos by this measure have happened over the past 10 years (including the June 2012 event). The top two — which each generated 64 significant reports — were the recent Dec. 15, 2021, and May 12 events.Heat is the common denominator in many of these events:The Dec. 15, 2021, derecho, which unleashed destructive winds from Kansas to Wisconsin, was preceded by temperatures as much as 30 to 40 degrees above normal. Both Iowa and Wisconsin saw their highest December temperatures on record that day.The May 12 derecho, which hammered the zone from eastern Nebraska to southwest Minnesota, erupted on a day with record-high temperatures from Texas to Maine.When a destructive and deadly derecho slammed eastern Canada on May 21, record-setting heat swelled over much of eastern North America, with 90-degree heat reaching as far north as Vermont.While temperatures were only somewhat above average ahead of the Aug. 10, 2020, Iowa derecho, the costliest thunderstorm disaster in U.S. history, it was still very warm and humid as a heat dome swelled over much of the Midwest and South.The June 2012 derecho occurred on the hottest June day on record in Washington — the temperature hit a blistering 104 degrees. Nashville (109) posted its highest temperature ever observed, while Raleigh (105) equaled its all-time high.It is not a coincidence that these derechos occurred on days with searing heat. Thunderstorms require instability, which acts as their fuel. It is often highest in environments that are exceptionally warm and moist. The amount of instability ahead of the 2012 derecho, for example, was extraordinary.Extreme derechos often form on the edges of heat domes that broil large swaths of the country; the corridor along which they form is sometimes described as a “ring of fire.” In these areas, brisk middle-atmospheric flow associated with the jet stream readily overlaps extreme heat and humidity — a volatile combination that can fuel violent storms.Climate change connectionsConsidering that scientists have found — thro …

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