An active month indeed, April 17, 1963 saw a significant long-track, violent F4 tornado track across the far northern part of the viewing area through Newton & Jasper to Pulaski counties.
According to Fujita, who plotted the damage path & researched this tornado, it had a continuous 70-mile path from Illinois to Indiana.
There is some evidence of a second in Pulaski County east of the end of the F4 track with more like F1 damage as tree & powerline damage occurred. This not plotted on the map & is from local press at the time, however.
18 people were injured in Jasper & Newton counties & 2 in Pulaski County. Of the 20, 16 were hospitalized for varying periods of time with varying injuries.
Final inflation-adjusted damage from the tornado alone was reportedly $23 million.
Hail up to 2.50" in diameter was reported just north of the tornado track. 1.75-2" hail was reported also at Star City & Royal Center. A testament to the strength of the updrafts in this outbreak, 3.5" diameter hail was reported in St. Joseph County, Indiana.
Considerable wind damage was also reported near Kentland & Brook (though not plotted on the SPC map).
It wasn't just severe storms here & only on April 17, but multiple rounds in the region surrounding us April 16-20. Also, April 29 was a big outbreak, "High Risk" day in our area.
Here are the storm reports, per SPC April 17:
Elevated MCS with rain & t'storms (large hail reports) was key to violent tornado the next day. It put out outflow boundary that laid up over north-central Illinois to nothern Indiana more than 12 hours prior to the F4. This boundary led for area of greater shear & a focus for an intense long-lived tornado.
Archived surface maps courtesy of NOAA:
This 1 p.m. map below is just prior to the erupton of severe storms, because by 4 p.m., they were in progress. Large, significant tornado was on the ground by 5 p.m.
The storms became a conglomerate & this large mass of storms was in Ohio to Pennsylvania at 1 a.m. on April 18.
However, the next severe weather outbreak was to come as surface low was already dropping out of Colorado toward Kansas.
This was the April 18-19, 1963 outbreak very near to our area that was mentioned at the beginning of this post.
This shows the convective precipitation rate (t'storm rainfall) in mm with the outbreak.
You can see the areas of heavy t'storm action & severe weather (albeit not the best resolution) in the 1 p.m. to 7 p.m. time frame with bulls-eye in the northern part of our viewing area.
This is an image that gives you an idea of how the radar may have looked as storms blew up & matured.
This is courtesy of George Mason University & NWS Chicago (specifically Meteorologist Jim Allsopp).
On the left is divergence while on the right is accumulated precipitation. They likely show where storms were very well & that the mode was supercellular going to more of a band or conglomerate of supercells.
These are the rainfall reports from the event. They varied from nothing to 1.57", according to National Weather Service COOP stations.
Below is a write-up on the main tornado rode that rode apparent outflow boundary. Given its violence, it is likely that there were no other storms south of it to interrupt its strong low-level flow.
Read below......hail accumulated & drifted deeply near Fort Wayne.
Tornado track (path) data courtesy of NOAA:
This image, courtesy of the Kankakee Daily Journal, shows a track meet underway at Kankakee High School as onlookers viewed the large tornado:
Rare footage of the tornado as it grows in size & strength in Kankakee County, Illinois:
Tornado in northwest Kankakee County (taken by Dorothy Riegel & courtesy of the Kankakee Daily Journal: