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  • Tim McGill

Sunday's Tornado Was Strongest Since 2015

Surveying The Damage

A Home Devastated By A Tornado In Naperville

I spent the afternoon Monday with Eric Lenning. He's the Meteorologist-in-Charge of Chicago's National Weather Service office in Romeoville. I was with him as he surveyed the damage form the Naperville/Willow Springs tornado. He was looking for clues to help assess the strength of the tornado along with it's width and path. The Naperville home pictured above suffered the worst damage. It was stripped down to just its foundation. Eric told me when they saw a "tornado debris signature" on doppler radar Sunday night that they already knew this was going to be a powerful storm. A TDS is sometimes referred to as a "debris ball". It is a signature on doppler radar that indicates debris being lofted into the air from a tornado.

There are at least 28 damage indicators that help determine the parameters of a storm like this. Those indicators along with eyewitness accounts and doppler data help the National Weather Service make their final determination. After a few hours of walking through the wreckage, the verdict was in. The Naperville/Willow Springs tornado was a powerful EF-3 on the Enhanced Fujita Scale with winds up to 145 mph. An EF-3 tornado produces "severe damage". This was the first confirmed tornado for northern Illinois this year. This is the first significant (EF-2+) tornado to impact the Chicago Metropolitan Area since an EF3 tornado hit Coal City in 2015. It was also the strongest tornado to impact DuPage County in 45 years.

Here is a description of the damage this type of tornado can bring:

Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations are badly damaged.

The survey team did complete their preliminary assessment of the tornado Plainfield to Romeoville tornado. It was rated and EF-0 tornado on the Enhanced Fujita Scale with maximum winds of 85 mph and a path length of just over three miles.

There were eight injuries from these storms but the good news is there were no fatalities. I was impressed and encouraged to see so many volunteers assisting in the clean up in Naperville.

A Delightful Day

Today started off feeling like fall with lows in the 40s in outlying areas. Average highs for today's date are around 82°. We will be around 10° below average today. The HRRR model has our highs today topping out in the lower to middle 70s.

Our dew points remain rather low for early summer. Dew points are the preferred measurement of moisture for meteorologists. They were well into the 60s over the weekend but have fallen into the 40s since then. They will gradually increase into the 50s overnight.

It will be a bit breezy today with west winds gusting to around 20 mph. Wednesday's winds will be stronger with gusts closer to 30 mph possible.

Slap on the sunscreen today because there should be plenty of sunshine although a few cumulus clouds will pop up during the afternoon. The best chance of rain over the next two days will be late tonight into early tomorrow. Nothing severe is expected but there will be some scattered showers and thunderstorms.

The National Blend Of Models has highs bouncing back closer to average Wednesday and then above Thursday. Highs will hover in the lower 80s this Friday through Tuesday next week before warming into the middle to upper 80s for the end of the week.

The long range temperature probability forecasts start off cool for the end of June and then bring us back to about average for the start of July. The 6-10 day forecast has outlooked us for below average temperatures overall from June 27th through July 1st. The longer range 8-14 day forecast also favors us for near normal temperatures overall from June 29th through July 5th. Average highs for late June and early July are in the lower to middle 80s.

The even longer range Subseasonal Experiment (SubX) temperature anomaly forecast favors us for above average temperatures overall for the first half of July. The average highs for this period are in the lower to middle 80s. The temperature anomaly forecast for the week ending July 9th has us outlooked for above average temperatures overall. The forecast for the following week ending on July 16th also has Chicago outlooked for above average temperatures overall too. It takes a close look at this second map to see we are the exception for Illinois. Most of the state is outlooked for about average or below average temperatures.

More Active Pattern To Bring Drought Relief

We are now up .67" above average for June rainfall. Sunday night's rain helped us achieve this rare surplus for this summer. We are still down though over six inches of rain below average since March 1st.

Here is a recap of my post from last week with details on our drought that does not include the recent rain:

Our ongoing drought in northern Illinois has both deepened and expanded according to the latest analysis from the US Drought Monitor. Almost 3% of the region is now in an extreme drought for the first time this year. That's the third of four levels of drought with "exceptional" being the fourth or worst level. 6.43% of Illinois is now in a severe drought (up from 4.58% last week). 9.18% of the state is in a moderate drought (up from 8.52% last week). The worst of the drought is centered in the northeast corner of the state and includes most of Lake County, all of McHenry county and portions of Cook, Kane, DeKalb and Boone counties. This does not take into consideration the rain that fell Thursday night into Friday morning.

Last Friday's post also included a look at Wisconsin, the Midwest and where the drought is hitting hardest, the western states. I'll have an update on our drought and the latest analysis from the U.S. Drought Monitor in this Friday's post.

The GFS model suggests a more active period coming starting tonight into early Wednesday and then on and off into this weekend. Look for periods of showers and thunderstorms. It doesn't look like a washout for any particular day but we will be dodging some rain the next several days.

The GFS model total rainfall forecast for our next round of rain through Sunday shows the potential for some significant help with our drought. It squeezes out around an inch and a third to an inch and a half of rain for most of us with some areas well west of the city receiving over two inches in total.

The long range precipitation probability forecasts are again a mixed bag for the end of June and start of July. The latest 6-10 day forecast has the Chicago area outlooked for below average precipitation overall from June 27th through July 1st. The longer range 8-14 day forecast also favors us (slightly) for above average precipitation overall from June 29th through July 5th.

Here is my 7 day forecast:

Today: Partly to mostly sunny, a bit breezy High: 75

Wednesday: AM sct. shower/t-storm possible, mostly cloudy, breezy Low: 60 High: 81

Thursday: Partly/mostly cloudy, sct. showers/t-storms mainly late Low: 67 High: 85 (cooler lakeside)

Friday: Mostly cloudy, sct. showers & t-storms Low: 70 High: 81

Saturday: Partly/mostly cloudy, sct. shower/t-storms possible Low: 68 High: 79 (cooler lakeside)

Sunday: Partly/mostly sunny, a few showers possible Low: 66 High: 80 (cooler lakeside)

Monday: Partly to mostly sunny Low: 67 High: 81



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