Storms March from Iowa to Atlantic – Millions without Power, At Least 8 Dead

There were 1,014 reports of severe weather yesterday according to the Storm Prediction Center – the vast majority of them coming from this single derecho. While a few places did experience hail, that was mainly confined to Iowa and Illinois – with up to 57 reports, 5 of those being “significant” hail over 2 inches in diameter. Once the storms got to and past Indiana, this primarily turned into a wind-only event. There were up to 955 reports of severe wind, with 35 of those being “significant” wind over 74mph – hurricane force.  ”Up to” is used because as data is confirmed, usually 10% or so of the numbers get shaved off. Still, quite an impressive and destructive day in terms of thunderstorms.

Among the highest wind gusts measured:

It will be days before power is fully restored in the effected regions, and with the heat wave expected to continue, this might not be the last derecho to be dealt with for a while. There is a significant degree of difficulty predicting where and when these storms will form until they actually get going – which is why they are not predicted to accompany every day of every heat wave.

In the event of a lack of severe thunderstorms, the number one threat in the week to come would then pivot to a heat wave that is expected to tighten its grip on the eastern 2/3 of the country. Storms and derecho events may be possible along the northern edges of the heat wave, as put by the National Weather Service office out of Chicago:

After a brief respite Friday, heat and humidity is forecast to build northward back into the area this weekend and continue through next week. Afternoon heat indices will likely climb above 100 degrees this afternoon south of interstate 80. The heat is forecast to spread north Sunday with afternoon heat indices near or possibly above 100 degrees across the entire area Sunday and each afternoon through next week. During the hottest afternoons heat index readings over 105 degrees are possible.

A front is forecast to stall out north of the region and it’s not out of the question that thunderstorms could push this front south and bring brief bouts of relief from the heat, but current indications are the heat wave will be rather unrelenting. The long duration of this heat wave will take a toll on those most susceptible to heat. Hospitals, emergency managers, and those responsible for handling heat related illness should prepare now for the potential of an extended heat wave.

derecho

Derecho comes from the Spanish word for “straight”.^[4] The word was first used in the American Meteorological Journal in 1888 by Gustavus Detlef Hinrichs in a paper describing the phenomenon and based on a significant derecho event that crossed Iowa on 31 July 1877.