Case of the Mondays

Monday proved to be an active jump start to the work week. Rounds of thunderstorms affected southern lower Michigan in the form of derechos and squall lines.

In Spanish, derecho is a word meaning ‘straight’. (I actually got far enough into Spanish in high school to know that by myself!) Straight or forward moving is a clear characteristic of these stampeding super storms. They are known to travel hundreds of miles. What technically defines a derecho is the sustained 58 mph winds. Typically regular squall lines have barely severe level wind gusts and hold up for a few hours before slowly deteriorating. Derechos on the other hand can last through the evening and into the next day. Derechos are commonplace during the summer as a warm atmosphere does nothing but fuel them on their journey.

Great animation of a derecho crossing Michigan in late May 1998. Line originated in Minnesota and finally fizzled out in western New York.

One thing to note on the radar screen is how the line of storms has a ‘bow’ to it. This hints that there are strong winds ‘pushing’ the storms ahead. This bow feature can occur in smaller short-lived squall lines, but nearly every derecho has a bowing area. Winds are expected to be at the maximum in the bow area.

I wanted brief that because what hit Michigan yesterday was kinda derecho/kinda not derecho. Lets take a look.

A few MCSs (Mesoscale Convective System) ventured into Michigan. The first one I noticed at about 9am was in central Michigan and looked to head south as time went on. This had little impact on my location. Some rain fell with a pick up in the wind, but I still got a nice shelf cloud out of it.

First complex is in mid Michigan, while the Chicago derecho crosses Lake Michigan.

An okay shelf cloud, saw some other impressive shots out there!

Reports came from Chicago that hurricane force winds (roughly 74mph) had dropped power to thousands and this complex now had its sights on western Michigan. I watched in amazement as the line crossed Lake Michigan in under an hour and quickly sent wind speed readings into the 70s on the shore of Michigan. I was getting excited but at the same time was thinking of things to prepare for power outages. 70mph winds can take down healthy trees and that would most definitely interact with power lines as well. Distracted by its rapid movement I ignored all that planning and just watched.

Line of storms from Chicago has the bow shape common with high winds. Sometimes small tornadic spin-ups can occur with the high winds. At this point it looked like southern Michigan was going to be wiped clean.

A strange thing happened at Lansing though. I didn’t notice it immediately, it was more shock when the line arrived at my location. I maxed at 20mph winds when I was expecting at least 50+. Wound up with a quarter inch of much needed rain though.

What I suspect, looking at the structure of the storm, is the line flattened out and lost that bow shape quality. This means that either winds become more uniform or died down a lot (perhaps a result of air mixing behind the earlier storms?).

Flattening of the storm definitely is clear looking at this image. Also note the rain cooled air temps behind the front.

Wundermap interpretation of the line about to hit Chelsea and southeastern Michigan.

Despite my reading of 20mph on the weather station, the Ann Arbor ASOS station reported a gust of 71 mph! Not sure how I missed that as the section that hit me likely would tear through Ann Arbor. But weather is weird like that sometimes. You wind some, you lose some.

Looking back, it is clear that most of the severe wind events took place before the line passed through Lansing.

Blue dots representing high wind reports and damage.

Impressive but scary looking photos out of Holland, MI. CMU Meteorology graduate Cort Scholten braved the downed power-lines to take a picture of Pine Avenue. An article about the damage and storm in Holland can be viewed here.

Power lines and you-name-it across Pine Avenue in Holland, MI. Photo by Cort Scholten.


About gweatherc
Live in Michigan and enjoy observing the weather. Want to pursue it as a career! Currently taking classes at Central Michigan University.

One Response to Case of the Mondays

  1. Dad says:

    Nice reporting information. I enjoyed this very much!
    Yhank you, Dad

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