March 28, 1920 - the original Palm Sunday Tornado Outbreak

[Hoosier]

I thought I'd make a thread as we come up on the anniversary.  This event is perhaps not as well known as the 1965 outbreak, but it wreaked havoc in a similar manner.  In fact, the 1920 and 1965 outbreaks were focused in essentially the same area.

This event produced over 30 tornadoes (and probably more as weaker tornadoes may not have been counted) and killed at least 153 with some estimates much higher than that. 

Here are some 500 mb and surface maps from that day:  

 

 

 

I've looked quite a bit into this setup to get an idea of what the conditions were like that day. This is obviously complicated by data issues or the lack thereof, but there is enough available to make some educated guesses.

First off, the system that spawned this outbreak had a very deep surface low. The surface low was located near Sioux City, Iowa during the early morning of the 28th and moved into southern Minnesota by noon (around the start time of the outbreak), reaching approximately 980 mb. Noon surface observations from Chicago revealed a temperature of 60 degrees with 84% relative humidity. When you know the temperature and RH, a very good estimate can be made for the dewpoint. In this case, the dewpoint at Chicago was around 56 at noon. Based on this and other obs, it is fair to assume that mid/upper 50's dewpoints made it at least as far north as Chicago and southern Michigan. Temperatures reached the 70's in much of IN/OH with even some 80+ readings noted.

Based on 700 mb and 500 mb charts, it appears that fairly steep mid level lapse rates existed across the area, which would've helped boost instability. CAPE is an integrated value so the following should be treated as rough estimates, but based on temps/dewpoints/lapse rates, I'm guessing that there would've been something like 1000-1500 J/kg CAPE in central/southern Michigan, trending toward 2000+ J/kg southward through IN/OH and south from there. Given this and the very strong system and presumably strong deep layer shear, we can only imagine what soundings would've looked like.

I put together a map of significant tornado tracks. Locations and ratings are from Tom Grazulis.

 

#1.....Vanzant, MO.....F2

#2.....S of Cortland, IL to NE of Sycamore, IL.....F2

#3.....SE of LaFox, IL to Wauconda, IL.....F3

#4.....N of Channahon, IL to Wilmette, IL.....F4 (likely 2 tornadoes)

#5.....E of Elkhorn, WI to W of East Troy, WI.....F2

#6.....SE of Baroda, MI to E of Sodus, MI.....F2

#7.....Bridgeview, IL to Chicago, IL.....F2

#8.....Cedar Springs, AL to N of Jacksonville, AL.....F3

#9.....N of Milner, GA.....F2

#10.....N of Deatsville, AL.....F2

#11.....Red Hill, AL to West Point, GA.....F4

#12.....W of Leroy, IN to Beatrice, IN.....F3

#13.....W of Hart, MI to Weare Township, MI.....F2 (started over Lake Michigan)

#14.....S of Freesoil, MI to Sherman Township, MI.....F2

#15.....S of Mishawaka, IN to NW of Union, MI.....F3

#16.....Cory, MI to S of Climax, MI.....F2 (possibly a family)

#17.....SW of Kalamazoo, MI.....F2

#18.....S of Mulliken, MI to S of Eagle, MI.....F3 (possibly a family)

#19.....Orlando, IN to SW of Coldwater, MI.....F4

#20.....S of Hickorys Corners, MI to Vermontville, MI.....F4

#21.....S of Orangeville, MI to ENE of Hastings, MI.....F3

#22.....Mason, MI.....F2

#23.....NNE of Fenton, MI.....F4

#24.....Uniondale, IN to Rabbs Corners, OH.....F4

#25.....SE of LaGrange, GA.....F3

#26.....S of Perry, MI to NE of Morrice, MI.....F2

#27.....SW of West Liberty, IN to S of Van Wert, OH.....F4 (possibly F5)

#28.....Saginaw, MI.....F2

#29.....Genoa, OH.....F2

#30.....S of Union City, IN to SE of Lightsville, OH.....F3

#31.....W of Fountain City, IN to N of Greenville, OH.....F4