The Plainfield, IL, F5 Tornado of August 28, 1990: A Case Study

In-depth discussion of the infamous Plainfield, IL, F5 tornado on August 28, 1990, which remains the only F5/EF5 to strike the US in the month of August since records began in 1950. In this video, we'll take a deep dive into the meteorology behind the event to determine how the Plainfield tornado may have happened despite, at first glance, a seemingly unfavorable environment for significant tornadoes. We'll also discuss some interesting features of the supercell and tornado, as well as compare it to another well-known Illinois violent tornado case that had a very similar background environment.

Thumbnail images via NWS Chicago.
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Chapters:

0:00 Introduction
3:21 Meteorological discussion
10:15 Sounding analysis
16:25 Radar analysis begins
17:41 Discussion of initial outflow dominance
20:19 Re-ingestion of outflow boundary
21:49 Similarities between Plainfield and 5-5-19 Tahoka, TX, case
24:07 Discussion of extreme CAPE not being main factor
27:57 Lightning anomalies in Plainfield supercell
32:44 Vortex constriction immediately preceding intensification to F5
34:14 Analog - Roanoke, IL, F4 - July 13, 2004
36:54 Wrap-up
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Resources:

NWS Chicago event page: https://www.weather.gov/lot/Plainfiel...

Fujita (1993): "Plainfield Tornado of August 28, 1990" - https://agupubs.onlinelibrary.wiley.c...

Seimon (1993): "Anomalous Cloud-to-Ground Lightning in an F5-Tornado-producing Supercell Thunderstorm on 28 August 1990" - https://journals.ametsoc.org/view/jou...

Johns (1982): "A Synoptic Climatology of Northwest Flow Severe Weather Outbreaks. Part I: Nature and Significance" - https://journals.ametsoc.org/view/jou...

Johns (1984): "A Synoptic Climatology of Northwest-Flow Severe Weather Outbreaks. Part II: Meteorological Parameters and Synoptic Patterns" - https://journals.ametsoc.org/view/jou...

Hocker (2004): "An Analysis of the Tornadic Tendencies of SW and NW Flow Severe Weather Events in the Southern Plains: 1992 - 2001" - http://weather.ou.edu/~jhocker/spc_pa...

Perez et al. (1997): "Characteristics of Cloud-to-Ground Lightning Associated with Violent Tornadoes" - https://journals.ametsoc.org/view/jou...

Plainfield damage aerial footage:    • August 28, 1990 Plainfield tornado  

Jay Orbik video of Plainfield supercell in DeKalb:    • August 28, 1990 supercell in DeKalb, IL  

Paul Sirvatka video of Plainfield supercell:    • WGN Weather Aug 29 1990  

Michael Marz Ashby, MN, EF4 footage:    • July 8th, 2020, tornado FULL CHASE  

NWS Lincoln (IL) event page on Roanoke: https://www.weather.gov/ilx/13jul04#:....

Tornado Archive: https://tornadoarchive.com/home/

SPC Violent Tornado Webpage: https://www.spc.noaa.gov/exper/outbre...
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