Tornado warnings are issued by weather forecasting agencies to areas in the direct path of a tornado or a severe thunderstorm capable of producing one. Modern technology like Doppler radar helps detect rotation in thunderstorms, enabling early warnings. Warnings are also issued based on visual sightings of tornadoes, funnel clouds, or wall clouds by weather spotters or the public. Ground truth reports are crucial, especially when radar coverage is unavailable or insufficient, such as in known gaps across the United States. These warnings advise people to take immediate cover.
March 1925: Tri-State Tornado
The Tri-State Tornado of March 1925 was the deadliest tornado in U.S. history, resulting in a significant loss of life. This event highlighted the need for improved tornado forecasting and warnings.
1925: High Tornado Death Rate
In 1925, the tornado death rate in the United States was 1.8 deaths per million people per year.
1938: Weather Bureau Rescinds Ban on "Tornado" Usage
In 1938, the Weather Bureau rescinded its ban on using the word "tornado" in weather products for emergency personnel, marking a step towards improved communication.
April 1947: Glazier–Higgins–Woodward Tornadoes
The Glazier-Higgins-Woodward tornadoes of April 1947 resulted in a high death toll, further emphasizing the importance of accurate and timely tornado warnings.
March 20, 1948: Tornado Strikes Tinker Air Force Base
On March 20, 1948, a tornado struck Tinker Air Force Base, causing significant damage to aircraft. This event led to the development of the first official tornado forecast five days later.
March 25, 1948: First Official Tornado Forecast and Warning
On March 25, 1948, the first official tornado forecast and warning were issued by U.S. Air Force Captain Robert C. Miller and Major Ernest Fawbush.
1948: Debate Over Tornado Forecast Reliability
In 1948, the accuracy of Miller and Fawbush's forecasts sparked a debate about the reliability of tornado predictions and which agencies should be responsible for issuing warnings.
March 25, 1949: Second Successful Tornado Forecast
On March 25, 1949, Miller and Fawbush issued their second successful tornado forecast, predicting tornadic activity in southeastern Oklahoma.
July 12, 1950: U.S. Weather Bureau Lifts Ban on Public Tornado Warnings
On July 12, 1950, the U.S. Weather Bureau officially lifted its ban on issuing public tornado warnings, acknowledging the need for timely warnings to protect lives.
1951: Severe Weather Warning Center Formation
In 1951, the Air Force established the Severe Weather Warning Center, which began issuing severe weather forecasts, including tornado warnings, to relevant agencies.
March 1952: First Experimental Public Tornado Forecast
In March 1952, the Weather Bureau issued its first experimental public tornado forecast. Although initially inaccurate, a subsequent forecast successfully predicted a tornado outbreak.
1954: First Televised Tornado Warning
In 1954, Harry Volkman broadcast the first televised tornado warning over WKY-TV in Oklahoma City, challenging the FCC's ban and prioritizing public safety.
1974: Decline of Tornado Alerts
The use of "tornado alerts," an advisory indicating imminent tornado formation, began declining after 1974 due to the increasing use of Doppler radar.
1974: Average Tornado Warning Time
In 1974, the average tornado warning time was -10 to -15 minutes, meaning warnings were issued after the tornado had already occurred.
1974: Discussion of the Last Tornado Alert
Following the 1974 Super Outbreak, serious discussions took place regarding the final elimination of the "tornado alert" advisory.
May 3, 1999: First Tornado Emergency Declaration
The first tornado emergency, an unofficial enhanced warning for extremely dangerous tornadoes, was issued on May 3, 1999, during the devastating Oklahoma City F5 tornado.
2000: Decreased Tornado Death Rate
By 2000, the tornado death rate had significantly decreased to 0.11 per million, largely due to improvements in the tornado warning system and increased public awareness.
September 20, 2002: Tornado Emergency During Initial Warning
On September 20, 2002, a tornado emergency was declared for the Indianapolis metropolitan area within the initial tornado warning issuance for an F3 tornado.
October 2007: Shift to Polygon-Based Tornado Warnings
In October 2007, the National Weather Service transitioned from county-based to polygon-based tornado warnings, allowing for more precise geographical targeting of warnings using storm paths determined by Doppler radar.
2008: Implementation of Emergency Management Ontario Red Alerts
Emergency Management Ontario began issuing red alerts in 2008 for areas under Environment Canada tornado warnings, sometimes overriding the original warning with local government or media participation.
March 2012: Introduction of Impact-Based Warning System
In March 2012, a pilot program for an Impact-Based Warning (IBW) system began in several Midwestern NWS offices, adding categorical tornado and damage threat indicators to warnings to better communicate risk.
March 2013: Expansion of Impact-Based Warnings
The IBW system expanded to 33 additional Central Region NWS offices in March 2013.
2013: Increased Average Warning Time
By 2013, advancements in technology had significantly increased the average tornado warning time to about 15 minutes, allowing for more effective preparation and evacuation.
March 2014: Further Expansion of Impact-Based Warnings
Eight more NWS offices, across the Eastern, Southern, and Western Regions, adopted the IBW system in March 2014.
2016: Agency-Wide Implementation of Impact-Based Warnings for Tornadoes
By 2016, the entire National Weather Service had implemented the Impact-Based Warning format for tornado warnings.
August 15, 2020: First Tornado Warning for Pyrocumulonimbus
On August 15, 2020, the NWS issued the first-ever tornado warning for a pyrocumulonimbus cloud, a fire-induced thunderstorm capable of producing tornadoes, in Lassen County, California during the Loyalton Fire.
July 2021: Full Implementation of Impact-Based Warnings
In July 2021, damage threat indicators were incorporated into severe thunderstorm warnings, marking the full implementation of the IBW format for all warning bulletins.
April 2023: Introduction of the TORNADO Act
Senator Roger Wicker introduced the TORNADO Act in April 2023, aiming to improve NOAA's severe weather prediction and communication by establishing a Hazard Risk Communication Office, optimizing data sharing, implementing advanced forecasting systems, and recommending Enhanced Fujita Scale revisions.