Predicting derechos has long bedeviled meteorologists. These powerful and fast moving storms, capable of producing winds similar in intensity to a Category 1 hurricane don’t occur often, but their occasional appearance often results in large amounts of damage, according to an article in Wired. The one which recently struck Iowa moved 770 miles across the Midwest in only 14 hours, damaging 10 million acres of crops, and leaving hundreds of thousands of people without power.
Unlike hurricanes, which typically provide significant warning, derechos can pop up almost instantly. As a result, predicting them remains a challenge, due to both a lack of data points from which to work, and the complex conditions from which a storm can emerge. Says Andrew Mercer, a meteorologist at Mississippi State, “All we have is these snapshots two times a day at 100 points for the entire country, which makes it really hard to get good wind data in the upper levels of the atmosphere.” Instead, Mercer observes, “What our models really need is much more frequent sampling, especially in the hours leading up to the event.”
Even when the data is present, it’s not always clear why a derecho forms. Says Patrick Marsh, science support chief at the National Weather Service Storm Prediction Center in Norman, Oklahoma, “We see these kinds of environments happen multiple times a year, but something almost always goes wrong that prevents a storm from evolving into a high-end situation.”
Source: https://www.wired.com/story/why-derechos-are-so-devilishly-difficult-to-predict/
