Indepth 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 wellknown Illinois violent tornado case that had a very similar background environment.

Thumbnail images via NWS Chicago.

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 Reingestion of outflow boundary
21:49 Similarities between Plainfield and 5519 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 Wrapup

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 CloudtoGround Lightning in an F5Tornadoproducing 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 NorthwestFlow 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 CloudtoGround 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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