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Hurricane Agnes tornado outbreak

Damage from an F2 tornado in Key West, Florida
Type	Tornado outbreak Tropical cyclone
Duration	June 18–19, 1972
Tornadoes confirmed	19 confirmed
Max. rating	F3 tornado
Duration of tornado outbreak	1 day, 13 hours, 45 minutes
Fatalities	7 fatalities, ≥ 135 injuries
Damage	$5,570,030 (1972 USD) $40.6 million (2024 USD)
Areas affected	Florida and Georgia
Part of the tornadoes of 1972 Most severe tornado damage; see Fujita scale Time from first tornado to last tornado

On June 18–19, 1972, Hurricane Agnes generated the third-deadliest tropical cyclone-related tornado outbreak in the United States since 1900, as well as the deadliest such tornado outbreak on record in Florida. The outbreak lasted about 38 hours and produced at least 19 confirmed tornadoes, though some studies suggested nearly a dozen more. Two of the tornadoes killed a total of seven people and were not classified as tornadoes by the National Weather Service until 2018. In Florida alone, the outbreak inflicted at least 135 injuries and destroyed 15 homes, while 119 homes received damage. Statewide, 217 trailers were destroyed and 196 trailers incurred damage. Additionally, six businesses were destroyed, while six others were damaged.

Background

The interaction of baroclinic features with Agnes resulted in a tropical cyclone with "hybrid" characteristics, which increased the threat of strong tornadoes with longer path lengths. The outbreak became the most significant tornado outbreak associated with a tropical cyclone prior to landfall. The presence of strong wind shear surrounding the tropical cyclone facilitated the development of strong tornadoes, including the greatest number of tornadoes of at least F2 intensity within one 24-hour period in Florida. Studies have suggested strong wind shear in the lower levels of the atmosphere is a common feature during tornado outbreaks involving the outer rain bands of tropical cyclones near Florida. Additionally, in Florida cases, the favored region for tornado outbreaks is the northeastern quadrant of northward-moving tropical cyclones. Agnes represented one of these cases.

Daily statistics

Confirmed tornadoes

• A number of undocumented tornadoes were located in 2002, but were overlooked at the time of the outbreak. Most of these remain unlisted in official records. For example, a brief tornado struck Everglades City. Trees were prostrated and portions of a home were transported for 1⁄4 mi (0.40 km). Additionally, a brief tornado damaged a roof and two airplanes in the town of Immokalee. Power lines were downed in the area.

June 18 event

June 19 event

See also

• List of tornadoes and tornado outbreaks
  • List of North American tornadoes and tornado outbreaks
  • List of tropical cyclone-spawned tornadoes

Notes

1. All losses are in 1972 USD unless otherwise noted.
2. An outbreak is generally defined as a group of at least six tornadoes with no more than a six-hour gap between individual tornadoes; however, the threshold varies slightly according to local climatology. On the Florida peninsula, an outbreak consists of at least four tornadoes occurring relatively synchronously—no more than four hours apart.
3. According to a reassessment in 2002, the outbreak resulted in thirty tornadoes in Florida and Georgia, including six F0 events, twelve F1 events, ten F2 events, and two F3 events on the Fujita scale. (Operationally, only seventeen tornadoes were confirmed.)
4. The Fujita scale was devised under the aegis of scientist T. Theodore Fujita in the early 1970s. Prior to the advent of the scale in 1971, tornadoes in the United States were officially unrated. While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007, Canada used the old scale until April 1, 2013; nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.
5. Historically, the number of tornadoes globally and in the United States was and is likely underrepresented: research by Grazulis on annual tornado activity suggests that, as of 2001, only 53% of yearly U.S. tornadoes were officially recorded. Documentation of tornadoes outside the United States was historically less exhaustive, owing to the lack of monitors in many nations and, in some cases, to internal political controls on public information. Most countries only recorded tornadoes that produced severe damage or loss of life. Significant low biases in U.S. tornado counts likely occurred through the early 1990s, when advanced NEXRAD was first installed and the National Weather Service began comprehensively verifying tornado occurrences.
6. ^ All dates are based on the local time zone where the tornado touched down; however, all times are in Coordinated Universal Time and dates are split at midnight CST/CDT for consistency.
7. ^ Prior to 1994, only the average widths of tornado paths were officially listed.

References

1. ^ Hagemeyer, Bartlett C.; Spratt, Scott M. (2002). Written at Melbourne, Florida. Thirty Years After Hurricane Agnes: the Forgotten Florida Tornado Disaster (PDF). 25th Conference on Hurricanes and Tropical Meteorology. San Diego, California: American Meteorological Society. Archived from the original (PDF) on October 16, 2008. Retrieved November 24, 2019.
2. ^ Hagemeyer 1997, p. 400
3. Hagemeyer 1997, p. 401
4. Grazulis 2001a, p. 206
5. ^ Storm Data Publication 1972, Events Reported
6. ^ Storm Data Publication 1972, Events Reported
7. Grazulis 1993, p. 141.
8. Grazulis 2001a, p. 131.
9. Edwards, Roger (March 5, 2015). "Enhanced F Scale for Tornado Damage". The Online Tornado FAQ (by Roger Edwards, SPC). Storm Prediction Center. Retrieved February 25, 2016.
10. "Enhanced Fujita Scale (EF-Scale)". Environment and Climate Change Canada. June 6, 2013. Archived from the original on March 3, 2016. Retrieved February 25, 2016.
11. "The International Tornado Intensity Scale". Tornado and Storm Research Organisation. 2016. Archived from the original on March 5, 2016. Retrieved February 25, 2016.
12. Grazulis 2001a, pp. 251–4.
13. Edwards, Roger (March 5, 2015). "The Online Tornado FAQ (by Roger Edwards, SPC)". Storm Prediction Center: Frequently Asked Questions about Tornadoes. Storm Prediction Center. Retrieved February 25, 2016.
14. Cook & Schaefer 2008, p. 3135
15. ^ "Hurricanes and Tornadoes". Central Pacific Hurricane Center. Archived from the original on November 3, 2008. Retrieved November 15, 2009.
16. Hagemeyer, Bartlett C. (1998). Written at Melbourne, Florida. 1.2 Significant Tornado Events Associated with Tropical and Hybrid Cyclones in Florida. 16th Conference on Weather Analysis and Forecasting. Phoenix, Arizona: American Meteorological Society. Archived from the original on June 16, 2004. Retrieved November 24, 2019.
17. Hagemeyer, Bartlett C.; Hodanish, Stephen J. (1995). Written at Melbourne, Florida. Florida Tornado Outbreaks Associated With Tropical Cyclones. 21st Conference on Hurricanes and Tropical Meteorology. Miami: American Meteorological Society. Archived from the original on June 17, 2008. Retrieved November 24, 2019.
18. ^ Storm Data 1972, pp. 76–8.
19. ^ Grazulis 1993, p. 1132.
20. ^ "Tornadoes". Naples Daily News. Naples, Florida. June 19, 1972.
21. Brooks 2004, p. 310.
22. ^ Storm Data 1972, p. 76
23. Storm Data Publication 1972, #9998261
24. Storm Data Publication 1972, #9998264
25. ^ Storm Data 1972, p. 77
26. Storm Data Publication 1972, #9998267
27. Storm Data Publication 1972, #9998269
28. Storm Data Publication 1972, #9998272
29. Storm Data Publication 1972, #990000003
30. Storm Data Publication 1972, #9998274
31. Storm Data Publication 1972, #9995664
32. ^ Storm Data 1972, p. 78

Sources

• Brooks, Harold E. (April 2004). "On the Relationship of Tornado Path Length and Width to Intensity" (PDF). Weather and Forecasting. 19 (2). Boston: American Meteorological Society: 310–19. Bibcode:2004WtFor..19..310B. doi:10.1175/1520-0434(2004)019<0310:OTROTP>2.0.CO;2.
• Cook, A. R.; Schaefer, J. T. (August 2008). Written at Norman, Oklahoma. "The Relation of El Niño–Southern Oscillation (ENSO) to Winter Tornado Outbreaks". Monthly Weather Review. 136 (8). Boston: American Meteorological Society: 3135. Bibcode:2008MWRv..136.3121C. doi:10.1175/2007MWR2171.1.
• Grazulis, Thomas P. (July 1993). Significant Tornadoes 1680–1991: A Chronology and Analysis of Events. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. ISBN 1-879362-03-1.
• Grazulis, Thomas P. (2001a). The Tornado: Nature's Ultimate Windstorm. Norman: University of Oklahoma Press. ISBN 978-0-8061-3538-0.
• Grazulis, Thomas P. (2001b). F5-F6 Tornadoes. St. Johnsbury, Vermont: The Tornado Project of Environmental Films.
• Hagemeyer, Bartlett C. (September 1997). "Peninsular Florida Tornado Outbreaks". Weather and Forecasting. 12 (3). Boston: American Meteorological Society: 400. Bibcode:1997WtFor..12..399H. doi:10.1175/1520-0434(1997)012<0399:PFTO>2.0.CO;2. S2CID 120588681.
• International Best Track Archive for Climate Stewardship (IBTrACS) (May 2021). IBTrACS browser (hosted by UNC Asheville) (Report). National Centers for Environmental Information – via World Data Center for Meteorology.
• National Weather Service (June 1972). Storm Data Publication (Report). National Centers for Environmental Information – via Storm Events Database.
• National Weather Service (June 1972). "Storm Data and Unusual Weather Phenomena". Storm Data. 6 (14). Asheville, North Carolina: National Climatic Data Center.

• F3 tornadoes
• Tornadoes of 1972
• Tornadoes in Florida
• Tornadoes in Georgia (U.S. state)
• 1972 natural disasters in the United States
• 1972 in Florida
• June 1972 events in the United States
• Tornado outbreaks spawned by tropical cyclones