2023-04-04 REPORTS: IA/IL


Jun 12, 2004
Sunrise, Florida
Good day all (Mods please adjust and feel free to add any other states if applicable)...

This is my chase summary for April 4, 2023 in Iowa (including the tornado in Marion County late in the day): On April 4, I looked at data in the morning, and decided on Iowa City and points south as an initial target area, with a second target farther west and south of Des Moines and eastward from there. A warm front was draped across southern Iowa, with a low pressure area entering the western part of the state by afternoon. I pretty much headed east on I-80 to Iowa City, then south on I-380 / Highway 218 towards Mount Pleasant, which was south of the warm front. A near 30 degrees F temperature gradient was encountered with this boundary, with Iowa City in the upper 50s, and upper 80s near Mount Pleasant. The atmosphere remained capped until late afternoon, with small storms firing east of the area (near the Quad Cities area), and a second complex farther west south of Des Moines. I did not want to cross the Mississippi River for the first storms, so I opted to head back west, mainly on SR 92, targeting the "tail-end" storms south of Des Moines. The SPC also issued mesoscale discussion 462, and subsequent tornado watch box 115, valid until 10 PM CDT for all target area(s). I headed west on SR 92 through Sigourney and continued west for about an hour, for a long-range intercept of the "tail-end Charley" storm south of Des Moines in the second target area, mainly in Marion County. This storm became severe, then tornadic by 7 PM, with a large tornado observed near Knoxville. The chase then turned north along SR 14, and east again towards Pella. The storm cycled again, and a possible large tornado (even wedge?) was observed northeast of Pella in darkening light near SR 102 and 163 and north of New Sharon. I wrapped up the chase at dark, taking Highway 63 north to I-80, then west into Des Moines for the night.

Full on-going chase log for 2023 (including this one) can be found here: www.sky-chaser.com

Details (on April 4, 7:00 PM): Interception and observation of an extremely severe (and tornadic) thunderstorm from Marion County near Knoxville / Pleasanton, Iowa and north and east towards Poweshiek County and along SR 92 / 12 and eventually towards SR 102 and Highway 63. The storm was a classic supercell storm, intercepted from the east long-range. A large elephant-trunk / rope tornado was encountered once close to the supercell storm, which listed rapidly northeast and dissipated near Lake Red Rock. A second, and larger possible tornado was also observed near Sully and Pella looking northeast after dark. The storm core was not penetrated, and hail hail up to 3". Rain, strong winds, and frequent lightning was observed with this storm as well. The storm had an impressive visual appearance, with RFD clear slot and striated updraft. Conditions causing the storm were surface heating, a low pressure area, warm front, and powerful upper-trough. Documentation was digital stills and HD video. A 2023 Hyundai Santa Fe was used to chase the storm. A tornado watch was in effect for the area until 10 PM CDT.


Above: These are two images, visible satellite for 23z on April 4 to the left, and a radar image of the Marion County, Iowa supercell at roughly 7:30 PM CDT to the right. The annotated satellite image shows the important synoptic features pertaining to storm development, as well as two areas of tornado-producing storms (south of Des Moines, Iowa and west-central Illinois). To the right, the base-reflectivity radar image (DSM) of the tornadic storm racing NE out of Marion County can be seen as it was cycling back up to produce a second tornado north of Sully, Iowa. The inset to the upper-left shows the velocity couplet of the supercell storm.


Above: Looking west along SR 92 and headed towards Marion County, Iowa, a "tail-end" supercell can be seen looming over the horizon. This is the storm being targeted at roughly 6:30 PM CDT. The view is to the west near Sigourney, Iowa. Note the impressive anvil blow-off - This storm was along the "triple-point" and warm front near the surface low, and experienced nearly 200 MPH of bulk wind shear from the low levels to 10km altitude (east winds at 35 Kts near surface 925 mb and WSW at 150 Kts with jet stream at 250 mb level)!


Above: View of rope tornado looking WNW out of the Knoxville / Pleasanton area in Marion County, Iowa at roughly 7 PM CDT. Wish I was closer in and had better view. But it is what it is.


Above: The storm quickly cycles up again, and produces another possible tornado (at least a rapidly developing wall cloud) near Sully, Iowa before 8 PM. The image has been brightened as it was getting dark, and the view is to the NE from near Pella, Iowa. This storm was moving NE at 50 to 60 MPH, so there was little chance of catching it at this point. I will justify using the term "Possible Tornado" in this case :)


Above: Highly enhanced (after dark) view of a possible large tornado from near Sully, Iowa. Lightning provided some illumination. This was another confirmed tornado according to emergency management, fortunately, over open country, but few chasers were on it. The view is to the NE, and I quickly lost sight of it after this and ended the chase.
Nice, Chris...you did exactly what I SHOULD have done...I even thought about jumping on 92 westbound while I was on my way south down 218, having rather fond memories of that highway from a mere four days before. However I continued moseying down to the Mt. Pleasant area, and by the time I started heading into Illinois it was too late for me to get on the right side of that supercell.
This was literally a backyard chase for me as the entire family of tornadoes occurred within 30 miles of my house. I targeted Burlington, IA with @Ethan Schisler, his fiance, and Storm Farnik. When it became clear the dominant supercell moving out of Lewis County, MO was going to track into southern Hancock and McDonough Counties in IL we headed back towards the home turf of Macomb, IL. As the storm became SVR warned we originally targeted the Industry area. When we intercepted about 6 mi south of Macomb a ragged wall cloud appeared and began to ingest scud as visible rotation ramped up and a few brief funnels persisted. After calling the NWS the first tornado warning was issued shortly thereafter. As the storm merged tornadogenesis was imminent.

The first tornado southeast of Industry was not immediately visible due to our position and the rain curtains sheltering it, but if you look at my second and third images you can see the cone within the rain shaft. That tornado dissipated and we narrowly avoided contact with a new tornado that developed west of Table Grove and moved through town just north of Fulton County Hwy 3. We pursued the cell east on US Hwy 136, catching several tornadoes west of Ipava before setting up shop on a bluff west of Duncan Mills about 2 mi west of US 24. Here, a gorgeous cone developed and this would be the parent tornado that produced the Lewistown EF-3. After repositioning due to hail, we settled on a great spot several miles south near the US 24/US 136 junction west of Havanna and watched the large cone move NNE into Lewistown whilst producing a satellite tornado to the right (see first image).

I have never seen structure this amazing in Illinois and I have never seen tennis ball-sized hail (4"+) in this region either. This was an incredible experience this close to home. We finished by checking back in with fellow chasers and residents of Table Grove and surveyed some of the damage for my news station (WGEM-10) before heading home.

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