Record Number of Tornadoes in the NWS Chicago Forecast Area in 2023

Record Number of Tornadoes in the NWS Chicago Forecast Area in 2023

Overview and Statistics

In 2023, there were 58 tornadoes in the NWS Chicago forecast area, which is the most to ever occur here in a calendar year since official NWS tornado records began in 1950. The previous record for the most tornadoes in a calendar year in the NWS Chicago forecast area was 30 in 2015, and the 10- to 20-year average is around 15. In addition to the anomalously large number of tornadoes in 2023, there were other noteworthy tornado statistics:

  • 2023 is the first year in which tornadoes occurred in the months of January, February, and March of the same year in the NWS Chicago forecast area.
  • No tornadoes occurred in the NWS Chicago forecast area during the month of June, which is typically one of the most active months for severe weather and tornadoes during an average year for our area. This was the 18th June since 1950 with no tornadoes in our forecast area. 
  • July 2023 featured a record number of tornadoes (27) in the NWS Chicago forecast area. The previous record was 4 in 1993. 
  • For the first time on record, all 23 counties in the NWS Chicago forecast area had at least one tornado occur in the same calendar year.
  • There were three days with more than 10 tornadoes each in the NWS Chicago forecast area in 2023, which is the first time on record that this has happened (official NWS tornado records date back to 1950). In fact, prior to this year, there had never been more than two days with more than 10 tornadoes in the NWS Chicago forecast area in the same calendar year. Including 2023, our forecast area has only had 16 calendar days with more than 10 tornadoes (since 1950). 
  • There were also a record number of EF-1 or stronger rated tornadoes (21) in the NWS Chicago forecast area in 2023, breaking the previous record of 19 from 1965.

Summary Graphic:

This year’s anomalous tornado activity was not just limited to the Chicago area — it was also a remarkably active tornado year in the state of Illinois as a whole.

  • There were 120 tornadoes confirmed in the state of Illinois during 2023, which ties 2003 for the 2nd most to occur in a calendar year. The most tornadoes to occur in a calendar year in the state of Illinois was 124 in 2006.
  • Illinois had at least one tornado occur in every month except for September, November, and December. This is the 7th time on record (since 1950) that the state has had tornadoes occur in at least 9 months of a calendar year.
  • A record number of tornadoes for the state of Illinois occurred in the months of January (10), March (37), and July (26).
  • On March 31st, 37 tornadoes touched down in Illinois, which is the 2nd most on record for a calendar day in the state behind 39 on April 19, 1996. One of these tornadoes was rated as an EF-3 and seven were assigned an EF-2 rating.

Summary Graphic:


March 31st Outbreak

  • A historic severe weather outbreak occurred across the Midwest, Southeast, and Mid-Atlantic regions of the United States on March 31 and April 1, 2023.
  • The 22 tornadoes that occurred in the NWS Chicago forecast area on March 31st tied the record for most tornadoes to occur in a single calendar day or a 24-hour span. This record of 22 tornadoes was initially set on June 30th, 2014 during the infamous “Double Derecho” event.
  • In the state of Illinois, a total of 37 tornadoes were confirmed, making it the state’s 2nd largest tornado outbreak on record, falling just shy of the 39 tornadoes that occurred on April 19, 1996. In the state of Indiana, a total of 23 tornadoes were confirmed, making it the state’s 5th largest tornado outbreak on record.
  • A total of 146 tornadoes in 16 states were confirmed nationally from the March 31, 2023 severe weather outbreak.
    • The March 31-April 1, 2023 outbreak became the 3rd largest tornado outbreak on record in the United States. Only the 2011 Super Outbreak (359 tornadoes) and the 1974 Super Outbreak (148 tornadoes) saw more tornadoes confirmed in the U.S.
    • 136 of the 146 tornadoes occurred within the span of 24 hours, which is also the 3rd most tornadoes to occur within a 24-hour span in the United States, also behind the 2011 Super Outbreak (which had 218 tornadoes occur in the U.S. within a 24-hour span at its peak) and the 1974 Super Outbreak (whose 148 tornadoes all occurred within a 24-hour span).
    • The highest rated tornado from this event was the Keota-Wellman tornado EF-4 tornado in Iowa.
    • A total of 11 EF-3 tornadoes were also confirmed in the states of Arkansas, Tennessee, Alabama, Iowa, Illinois, Indiana, and Delaware.

Summary Graphic: 

Additional information about the March 31, 2023 tornado outbreak can be found here.  


July Outbreaks

  • There were two localized tornado outbreaks that occurred in the area in July 2023:
    • July 12: 13 tornadoes touched down across northeastern Illinois
    • July 28: 13 tornadoes touched down across northeastern Illinois and northwestern Indiana
    • Both July 12th and July 28th share the record for the most tornadoes to occur on a calendar day (or within a 24-hour period) in July in the NWS Chicago forecast area. 
  • In addition to the two localized tornado outbreaks, an EF-0 tornado touched down in central DuPage County during the evening of July 14th. 
  • In total, the 27 tornadoes across three separate events marked a record for the most tornadoes during the month of July in the NWS Chicago forecast area. The previous record was 4 in July of 1993. 

Summary Graphic: 

Additional information about the July 12, 2023 localized tornado outbreak can be found here

Additional information about the July 14, 2023, EF-0 tornado in DuPage County can be found here.  

Additional information about the July 28, 2023 localized tornado outbreak can be found here


Local Tornado Climatology

With 58 tornadoes across 9 separate severe weather events, 2023 featured an anomalously large number of both tornadoes and tornado events. In a typical year, around 15 tornadoes touch down in the NWS Chicago forecast area (when considering the 10- and 20-year averages). 

Tornado Reports

Any Tornado Reports

(F/EF0+ or EF-U)

Significant Tornado Reports

(F/EF2+)

Non-Significant Tornado Reports

(F/EF0-1 or EF-U)

10-Year Average 16 reports 1 reports 14 reports
20-year Average 14 reports 1 reports 12 reports
30-year Average  12 reports 1 reports 10 reports 
Database Average 9 reports 2 reports 7 reports
Year with Most Reports 2023 (58 reports) 10 (1965) 2023 (55 reports)

10-year average range: 2011-2020   |   20-year average range: 2001-2020   |    30-year average range: 1991-2020   |   Database average range: 1950-2020

In addition, a typical year will feature between 5 and 6 days with at least one tornado report. While 2023 was remarkably active with 9 days with at least one tornado, it was not the most active as 2010 saw 10 days with at least one tornado. 

Tornado Days

Any Tornado Days

(F/EF0+ or EF-U)

Significant Tornado Days

(F/EF2+)

Non-Significant Tornado Days

(F/EF0-1 or EF-U)

10-Year Average 6 days 1 day 6 days
20-year Average 5 days 1 day 5 days
30-year Average 5 days 1 day 4 days
Database Average 5 days 1 day 4 days
Year with Most Days 2015 (10 days) 1975 (5 days) 2015 (10 days)

10-year average range: 2011-2020   |   20-year average range: 2001-2020   |    30-year average range: 1991-2020   |   Database average range: 1950-2020

Tornado season in northern Illinois typically spans from April through September and peaks in May and June. In spite of the record-breaking number of tornadoes, 2023 featured an unusual monthly distribution of tornadoes with the most days with at least 1 tornado occurring in July. In addition, there were no tornadoes during the month of June, which is typically one of the “busiest” months for severe weather. 2023 also featured tornadoes during the consecutive months of January, February, and March, which has not been recorded since official NWS tornado records began in 1950. Finally, in addition to June, no tornadoes occurred in the months of April, September, October, November, and December. 

20-Year Average

2023


Advancements in Meteorology

The number of tornadoes in 2023 was certainly anomalous. However, the majority of tornadoes in the NWS Chicago forecast area were not considered to be “strong” (i.e. rated EF-2 or greater). While the number of such weak tornadoes has increased over the past few decades, the number of strong tornadoes has remained relatively steady. Why is the number of brief and weak tornadoes increasing?

1). Better understanding of the types of storms that produce tornadoes

Since the late 1900s, meteorologists have been gaining a better understanding of the types of storms that produce brief and weak tornadoes. Contrary to supercell thunderstorms, which are responsible for the majority of long-tracked, violent, and deadly tornadoes, the type of storm that often produces brief and weak tornadoes is known as a quasi-linear convective system (QLCS), or squall line. That is not to say that QLCS/squall line tornadoes are not dangerous. Rather, our understanding of how they form and the ways to detect them both in real-time and after a storm have dramatically improved. Perhaps unsurprisingly, the majority of tornadoes that occurred in the NWS Chicago forecast area in 2023 were produced by squall lines. 

Example article analyzing the characteristics of circulations that produced tornadoes during the June 30, 2014 localized tornado outbreak in northeastern Illinois and northwestern Indiana. Several staff members of NWS Chicago were co-authors of the article. Link to Article.

2). Better capability to detect tornadoes

Over the past few decades, radar scanning strategies and resolution have dramatically improved the ability for meteorologists to anticipate and detect tornadoes before and while they are occurring, respectively. In the most aggressive scanning strategy, meteorologists have access to new scans at the lowest elevation in as few as 3 to 4 minutes. In addition, staff at NWS Chicago have access to data from FAA-owned and operated terminal Doppler radars TORD, TMDW, and TMKE, which can provide a new scan in as few as 60 seconds with a coverage area across most of the Chicago metropolitan area. Furthermore, the addition of dual-polarization capability to analyze the “shape” of what our radar is seeing can provide confirmation that a tornado is occurring by identifying lofted debris. As a result, NWS meteorologists sometimes know for a fact that a tornado occurred prior to receiving reports of damage! For these reasons, NWS meteorologists have a plethora of data at their fingertips to monitor and anticipate storm evolution, including detecting brief and weak tornadoes.

Example of a “Tornado Debris Signature” using radar reflectivity, storm-relative velocity, correlation coefficient, and differential reflectivity, during the June 20, 2021 Naperville to Willow Springs EF-3 Tornado View of the Naperville to Willow Springs EF-3 tornado from KLOT (top left, bottom left), TORD (top right), and TMDW (bottom right), between 11:05 and 11:14 PM June 20, 2021. Note the increased temporal resolution provided by TORD and TMDW.  

3). Better methods to detect brief damage paths and collect damage reports

With the rise of social media in the past two decades came a corresponding improved ability to interact favorably with the public. Our social media channels are often a go-to resource for us to collect reports and photos of storm damage, which can then be compared to radar data to assess whether an investigation of whether a tornado occurred is needed. It is rare for notable storm damage that occurs in populated areas to go unreported to the NWS in some shape or form. Hence, it is easier to locate damage produced by brief and weak tornadoes simply through more reliable and frequent reports. In addition, NWS meteorologists have access to high resolution satellite data that is collected after severe weather events that can be used to identify potential tornado damage paths, particularly through agricultural and rural areas. After identifying potential damage paths, NWS meteorologists often work with local Emergency Management officials to confirm that damage indeed exists, and then compare the damage path with radar data to determine if a tornado occurred. The use of drone footage is also incredibly helpful to help confirm narrow or short paths of damage in agricultural or rural areas. 

Example damage path through an agricultural field near Sandwich, IL identified in Sentinel2 satellite data. The path of damage was later confirmed to be caused by an EF-0 tornado after the video footage collected from a drone that was flown along the path of damage was shared with the NWS, additional reports of damage were collected, and rotation was confirmed via radar. (July 28, 2023)

In all, it is easier to identify, detect, and confirm brief and weak tornadoes today compared to decades of the past. For this reason, it is possible that the number of brief and weak tornadoes that occurred in prior decades were undercounted.

However, even if you remove all EF-U and EF-0 tornadoes from each year’s tornado count, 2023 still featured more EF-1+ tornadoes (whose counts are less likely to be affected by these advancements in meteorology and technology) in the NWS Chicago forecast area than any other year, so it was a remarkably active tornado year in northeast Illinois and northwest Indiana any way that you slice it.

Summary Graphic: 


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