The National Weather Service has officially confirmed that powerful and devastating storms during a record-setting stretch of warm weather on December 15 in Michigan, and several other states in the Great Plains and Midwest, was part of a weather event that has never occurred in the month of December since records have been kept in the United States.

Other than a major wind event and record high temperatures in the lower 60s in parts of Michigan, the state did not experience any of the tornadoes and wind bursts that were part of what meteorologists have now confirmed was a 'serial derecho'. But an area in the Upper Peninsula experienced an extremely rare December thunderstorm, just nine days before Christmas, after the serial derecho weakened before coming through that area. According to the Weather Channel, the Houghton County Memorial Airport recorded a temperature of 51 degrees just after midnight on December 16, a record high for the date. Average highs are just 27 degrees there this time of year.

Here is the definition of a serial derecho, according to the National Weather Service:

They are produced by multiple bow echoes (storms with strong winds that bow outward) embedded in an extensive squall line (typically many hundreds of miles long) that sweeps across a very large area, both wide and long. This is mostly driven by a strong area of low pressure and very strong winds present in the atmosphere.

 

Some meteorologists describe a derecho as being like an inland hurricane, except it has no eyewall. The winds come in a straight line and then appear to "bow" out on the radar, potentially causing widespread damage. Several have happened in Michigan over the years, but most often in the late Spring and Summer months.

So far, around 45 tornadoes have been confirmed in preliminary research of the December 15 storms with Minnesota, Nebraska, and Iowa seeing the worst of it, including five deaths.

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