Tornado_outbreak_of_April_30_–_May_2,_1967

Tornado outbreak of April 30 – May 2, 1967

Tornado outbreak of April 30 – May 2, 1967

Add article description

A destructive severe weather episode affected portions of the Midwestern and Southern United States from April 30–May 2, 1967. It consisted of two consecutive tornado outbreaks that generated at least 38 tornadoes, causing 13 fatalities and 90 injuries. All of the deaths occurred on April 30, which is known as the 1967 Iowa–Minnesota tornado outbreak, or Black Sunday, to residents of Iowa and southern Minnesota. That day spawned a total of 21 tornadoes, devastating the towns of Albert Lea and Waseca, Minnesota.[6][7][nb 2][nb 3]

Quick Facts Type, Duration ...

Background

Surface weather analysis for April 30, 1967, at 1:00 a.m. EST (06:00 UTC), the morning prior to the tornado outbreak.

Beginning on April 30, 1967, a potent mid-latitude cyclone generated severe weather, including blizzards and severe thunderstorms, across a broad region extending from the northernmost High Plains and Rocky Mountains to the Mississippi and Ohio River valleys. These conditions occurred within a seventy-two-hour-long span.[18] By 1:00 p.m. CDT (12:00 p.m. CST; 18:00 UTC) on April 30, a low-pressure area of at most 984 millibars (29.06 inHg) was centered near Pierre, South Dakota, with a stationary front superimposed from north of Sioux Falls to near LaCrosse, Wisconsin. Nearby, a warm front also attended from south of Sioux Falls to near Des Moines, Iowa, and St. Louis, Missouri.[19] As the warm sector advanced into northernmost Iowa and southern Minnesota, surface air temperatures rose into the 60s and low 70s °F, while dew points reached the 60s °F. Winds at the surface ranged from 15 to 25 miles per hour (24 to 40 km/h) out of the east-southeast.[19] By 7:00 p.m. CDT (6:00 p.m. CST; 00:00 UTC), the warm front migrated to near the Minnesota-Iowa border, while the mid-level trough associated with the surface cyclone acquired a negative tilt. At the same time, a strong jet stream brought deep-layer wind shear over portions of northern Iowa and southern Minnesota—indicating favorable conditions for tornadogenesis.[20]

Daily statistics

More information FU, F0 ...
More information Date, Total ...
More information State, Total ...

Confirmed tornadoes

April 30 event

More information F#, Location ...

May 1 event

More information F#, Location ...

May 2 event

More information F#, Location ...

See also

Notes

  1. [N 1]
    All losses are in 1967 USD unless otherwise noted.
  2. [N 2]
    An outbreak is generally defined as a group of at least six tornadoes (the number sometimes varies slightly according to local climatology) with no more than a six-hour gap between individual tornadoes. An outbreak sequence, prior to (after) the start of modern records in 1950, is defined as a period of no more than two (one) consecutive days without at least one significant (F2 or stronger) tornado.[8][9][10][11][12][13]
  3. [N 3]
    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.[14] While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007,[15] Canada utilized the old scale until April 1, 2013;[16] nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.[17]
  4. [N 4]
    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.
  5. [N 5]
    Prior to 1994, only the average widths of tornado paths were officially listed.[25]

References

  1. [1]
    National Weather Service (May 2019). Events reported between 04/30/1967 and 05/02/1967 (3 days). Storm Events Database (Report). National Centers for Environmental Information. Retrieved 18 November 2019.
  2. [2]
    National Weather Service (30 September 2019). Grazulis, Thomas P.; Grazulis, Doris (eds.). Tornado History Project: Maps and Statistics. Tornado History Project (Report). The Tornado Project of Environmental Films. Retrieved 2 January 2021.
  3. [3]
    National Weather Service (30 September 2019). Grazulis, Thomas P.; Grazulis, Doris (eds.). Tornado History Project: Maps and Statistics. Tornado History Project (Report). The Tornado Project of Environmental Films. Retrieved 2 January 2021.
  4. [4]
    National Weather Service (May 2019). Events reported between 04/30/1967 and 05/02/1967 (3 days). Storm Events Database (Report). National Centers for Environmental Information. Retrieved 18 November 2019.
  5. [5]
    National Weather Service (May 2019). Events reported between 04/30/1967 and 05/02/1967 (3 days). Storm Events Database (Report). National Centers for Environmental Information. Retrieved 24 September 2019.
  6. [6]
    Hatfield, Karen (2007). "Black Sunday April 30, 1967". National Weather Service Weather Forecast Office Twin Cities, MN. Minneapolis–Saint Paul: National Weather Service. Archived from the original on 12 October 2012. Retrieved 23 September 2019.
  7. [7]
    Hatfield 2017, pp. 3–4.
  8. [8]
    Schneider, Russell S.; Brooks, Harold E.; Schaefer, Joseph T. (2004). Tornado Outbreak Day Sequences: Historic Events and Climatology (1875-2003) (PDF). 22nd Conference on Severe Local Storms. Hyannis, Massachusetts: American Meteorological Society. Retrieved 17 September 2019.
  9. [9]
    Hagemeyer 1997, p. 400.
  10. [10]
    Grazulis 2001, p. 206.
  11. [11]
    Hagemeyer 1997, p. 401.
  12. [12]
    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 16 October 2008. Retrieved 24 November 2019.
  13. [13]
    Grazulis, Thomas P. (2001). The Tornado: Nature's Ultimate Windstorm. Norman: University of Oklahoma Press. p. 206. ISBN 978-0-8061-3538-0.
  14. [14]
    Grazulis 1993, p. 141.
  15. [15]
    Edwards, Roger (5 March 2015). "Enhanced F Scale for Tornado Damage". The Online Tornado FAQ (by Roger Edwards, SPC). Storm Prediction Center. Retrieved 25 February 2016.
  16. [16]
    "Enhanced Fujita Scale (EF-Scale)". Environment and Climate Change Canada. 6 June 2013. Archived from the original on 3 March 2016. Retrieved 25 February 2016.
  17. [17]
    "The International Tornado Intensity Scale". Tornado and Storm Research Organisation. 2016. Archived from the original on 5 March 2016. Retrieved 25 February 2016.
  18. [18]
    Hatfield 2017, p. 7.
  19. [19]
    Hatfield 2017, p. 10.
  20. [20]
    Hatfield 2017, p. 15.
  21. [21]
    Grazulis 1993, pp. 1089–1090.
  22. [22]
    USWB 1967a, pp. 27, 30, 36.
  23. [23]
    Hatfield 2017, p. 14.
  24. [24]
    USWB 1967b, pp. 42, 45–47, 52, 54–55.
  25. [25]
    Brooks 2004.
  26. [26]
    USWB 1967a, p. 36.
  27. [27]
    Grazulis 1993, p. 1089.
  28. [28]
    USWB 1967a, p. 27.
  29. [29]
    Grazulis 1993, p. 1090.
  30. [30]
    Storm Data Publication 1967a, #10052249
  31. [31]
    Storm Data Publication 1967a, #10013117
  32. [32]
    Hatfield 2017, p. 22.
  33. [33]
    Storm Data Publication 1967a, #10052251
  34. [34]
    Storm Data Publication 1967a, #10052255
  35. [35]
    USWB 1967b, p. 54.
  36. [36]
    USWB 1967b, p. 42.
  37. [37]
    USWB 1967b, p. 46.
  38. [38]
    USWB 1967b, p. 47.
  39. [39]
    USWB 1967b, pp. 54–55.
  40. [40]
    "NWS Damage Survey for April 22 2020 Polk County Tornado Event". Iowa Environmental Mesonet. National Weather Service Weather Forecast Office in Houston, Texas. April 24, 2020. Retrieved April 24, 2020.
  41. [41]
    Storm Data Publication 1967a, #10132367
  42. [42]
    USWB 1967b, p. 45.
  43. [43]
    USWB 1967b, p. 55.
  44. [44]
    Storm Data Publication 1967a, #10033059
  45. [45]
    Storm Data Publication 1967b, #10033060
  46. [46]
    Storm Data Publication 1967b, #10033061
  47. [47]
    USWB 1967b, p. 52.

Sources
Share this article:

This article uses material from the Wikipedia article Tornado_outbreak_of_April_30_–_May_2,_1967, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.