On Trading Hurricanes for Tornadoes: Understanding Extreme Weather in Chicago

derecho

June 30, 2014. Photo credit: Nick Ulivieri  www.nickulivieriphotography.com

One year ago, as I started packing up the Connecticut house to move here, my husband emailed me this picture of the foreboding early evening sky over the city.

It was a derecho, packing winds gusts over 80 mph, the kind of wind that can rip the roof off your house, or knock your trees and power lines down.

This was a new term for me to add to my extreme weather vocabulary. Coming from the Northeast, I was intimately familiar with a few others, like Nor’easter, Hurricane Irene, and Hurricane Sandy.

Of these, Hurricane Sandy affected my family the most. For the better part of two days, our little home was blasted with wind gusts ranging from 60 to 80 mph. Trees toppled everywhere, on roofs, power lines, blocking roads. Transformers exploded everywhere in the night sky and it was like watching Fourth of July fireworks, at the end of October. While I was unhappy to be without power and heat for three days with a newborn, we were very, very lucky. We had a home, many didn’t.

Large sections of Manhattan were plunged into darkness, fires raged, gas shortages persisted. Was this a storm or Armageddon?

So now, back to the Midwest. Let’s add another vocabulary word: tornado. Within 24 hours of my arrival in Illinois, a Tornado Watch was issued for our area. Between that and the derecho, I came down with some major weather anxiety.

Growing up in Upstate New York, we had our share of severe thunderstorms, but less so in suburban NYC where the Long Island Sound generally sheltered us from this extreme weather risk. Tornadoes do touch down but they were rare, and when they did, they tended to be EF-1 or more commonly, EF-0 on the Enhanced Fujita Scale.

As a result, on April 9 when I witnessed the power an EF-4 tornado can unleash live on The Weather Channel as it ravaged the small town of Fairdale about an hour away, this was a whole new world to me. That entire day my eyes were glued to either my computer screen where I was toggling between the websites for the National Weather Service and Accuweather radar, or The Weather Channel on the TV.

I will be honest; I was terrified that day. My adrenaline output was astronomical. I have always been the girl who runs to the basement after seeing a bright flash outside the window, always scared where I was would be struck by lightening. I know that is not true but still, I watched the radar closely, trying to determine the chances of a direct hit. Were the storms getting stronger or weaker? Were they drifting east towards me or drifting more to the southeast? How about the rain early in the day, could that forestall the severe weather threat late in the day?

The same scenario replayed itself one week ago. Instead of settling down to watch the Cubs game, I huddled by the computer,trying not to look at the greenish sky at sunset. That can’t be good, I thought.

It became quickly clear to me the weather here is fundamentally different than what I have known most of my life. So I wanted to understand our weather, not live in fear of it.

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To provide a meteorological perspective to the extreme weather risk in Chicagoland, I enlisted the help of the Illinois Storm Chasers. Adam Lucio (pictured left) and Danny Neal (on the right) have been chasing the not-so-friendly skies over the past several years.

Adam has been obsessed by storms all his life, “I was attracted to the power of storms, the chaos of the environment.”

On the other hand, initially Danny was scared of storms, just like me. His fear was shaped by the destructive Plainfield F-5 tornado on August 28, 1990 when he was three. As the storm approached, his dad grabbed him out of the inflatable pool he was playing in and rushed him to the basement. For years after, he thought every storm was going to be like that. With help from his family and teachers, he was encouraged to learn all he could about these storms so he could overcome his fear. He certainly did that, and much more. “I respect it now, I don’t fear it.”

Since moving here, I have heard some folks say we are in Tornado Alley so I asked if that were true. Technically, Chicagoland is not located in Tornado Alley, at least not in the traditional territory which is Texas straight up to North Dakota, and a little further east into western and central Iowa down to Missouri but we are on the fringe so we get some of the action.

Still, it’s a bit more complicated as Danny elaborated. “My belief is there is no end to tornado alley, it just shifts throughout the year, it shifts with the jet stream.” It starts as “Dixie Alley” in the deep South, then shifts to the traditional Tornado Alley in the Plains, then drifts further north up into Canada. This is because while there could be “thunderstorms all day long, they need that jet stream energy to become stronger, more long lived, more violent” to become a thunderstorm with a rotation. And the jet stream moves around all year long.

While not in Tornado Alley proper, this entire area is at risk. “The popular myth around here is that Lake Michigan protects this area from tornadoes, that tornadoes can’t happen in the city. That is completely untrue. I can name more than one instance in which a tornadic thunderstorm has tracked across the area and waited until it got to Lake Michigan to actually touch down.” This is what happened two weeks ago.

The popular myth around here is that Lake Michigan protects this area from tornadoes, that tornadoes can’t happen in the city. That is completely untrue.

As it turns out, according to them we are located in what they call “Derecho Alley”. By definition, a derecho is a widespread, long-lived band of thunderstorms which must have winds of at least 58 mph and travel at least 240 miles. This time of year, conditions here favor derechos more compared to tornadoes when the jet stream is up in Canada. Adam provided some meteorological detail here, “Underneath the jet stream sits a dome of warm, hot air in the Plains. What happens is these storms form along a ridge of that hot dome of air. The storms love that area of enhanced wind shear and they ride that dome into this area. That puts us at risk for these derecho type storms.”

The good news from Adam and Danny: our weather could actually be much worse. “When weather systems first develop, that’s when they are going to produce their most intense severe weather. Well, this usually happens in the Plains. These systems then weaken as they move east overnight and spread convective debris into our area for the morning, giving us rain. If the cloud cover remains through the day, it prevents the atmosphere from further destabilizing. However, if the clouds break up allowing the sun to shine, that heats up the atmosphere and produces more severe weather. “It’s a critical piece of that puzzle, how that morning activity plays out.”

November 17 2013 tornado

Photo credit: Adam Lucio, Illinois Storm Chasers

I have been here not even a year and I have discovered that some people talk about the big storms in terms of dates, instead of names as we did on the East Coast. There it was Irene, Sandy. Here, that shortlist of dates usually includes November 17, 2013. I always thought of tornadoes as spring weather phenomenon but yes, there is a fall tornado season here. It’s shorter and generally tamer due to the colder temperatures but in their estimation, every 5 years or so the conditions can produce a major one, like it did on this day. On that day the weather system developed in eastern Iowa/western Illinois, not out in the Plains, so the severity was greater.

It became clear to me throughout our conversation that the updates they post to their Illinois Storm Chasers Facebook page have a primary intention: keeping us safe. For this, I thank them. As frequent as their updates are, they are quick to point out it’s important to have more than one source for the weather, especially on severe weather days when they are out in the field and information is flying fast and furious.

So now I understand.

In terms of my goal of learning to live with our weather without fear, Danny had a great perspective I could learn from.

“Of the 365 days in a year, only about 5 or 10 are favorable for that kind of weather.”

That’s important to remember. It worked for him and while I don’t see myself running out the door to chase storms, it does keep my blood pressure within normal limits on severe weather outbreak days. As each of these days passes on by as quickly as the wind that ushers them in, I have become increasingly calmer and dramatically less fearful. Goal accomplished.

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