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Tornado outbreak of August 6, 1969

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Tornado outbreak of August 6, 1969
Splintered debris with trees leaning in the background
Damage to cabins near the current Lake Roosevelt Resort just north of Outing, Minnesota
Tornado outbreak
Tornadoes14
Maximum ratingF4 tornado
DurationAugust 6, 1969
Highest gusts60 kn (69 mph; 110 km/h) in Iowa[1]
Largest hailin (2.5 cm) in Clearwater County, Minnesota[2]
Overall effects
Fatalities15+
Injuries109
Damage$5,120,000 ($42,540,000 in 2024 USD)[note 1]
Areas affected

Part of the tornadoes and tornado outbreaks of 1969

On August 6, 1969, a destructive tornado outbreak affected portions of the Upper Midwest—principally north-central Minnesota. The severe weather event generated 14 confirmed tornadoes, killed 15 people, and caused 109 injuries. To date, the outbreak remains the deadliest on record in the North Woods region of Minnesota. It is also known as the 1969 Minnesota tornado outbreak and the 1969 North Woods tornado outbreak. The most destructive tornado of the outbreak was a 33-mile-long (53 km) violent F4 that leveled miles of timberland and farmland across portions of Crow Wing, Cass, and Aitkin counties in Minnesota, killing at least 12 people and injuring 70 others.[3][4][note 2]

Background

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An F4 tornado caused major damage to many cabins and wide swaths of forest on both sides of Lake Roosevelt in the Outing, Minnesota, area.

Very warm, humid, summertime air had pushed into central and southern Minnesota on August 6, 1969. Minneapolis recorded a high temperature of 93 °F (34 °C) with dew points near 70 °F (21 °C). Meanwhile, strong upper-level winds over northern Minnesota and an approaching cold front from the west added the needed ingredient for the strong storms.[3] Two distinct thunderstorms formed approximately 45 mi (72 km) apart and tracked east-northeastward across Minnesota at 50 mph (80 km/h).[6] These parallel storms generated 14 tornadoes, killing 15 people and injuring 109.

The first tornado of the day, rated F0, touched down at 1:15 p.m. CDT (12:15 p.m. CST; 18:15 UTC) in Beltrami County.[3][7] The main tornado event started about three hours later in Cass County when an F3 tornado touched down southwest of Backus, injuring four people.[8] The most damaging tornado of the outbreak touched down at 4:48 p.m. CDT (3:48 p.m. CST; 21:48 UTC) in Crow Wing County. It achieved F4 strength, traveling 33 miles (53 km) through Crow Wing, Cass and Aitkin counties. The area around Outing was especially hard hit by this tornado, where 11 deaths and 40 injuries occurred on the shores of Roosevelt Lake.[3]

Several more strong tornadoes touched down over the next two hours, killing one person near Jacobson and two people near Two Harbors.[3] Damage and casualties were limited, however, because most of the twisters, however large in size, struck rural areas.[9]

Confirmed tornadoes

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Confirmed tornadoes by Fujita rating
FU F0 F1 F2 F3 F4 F5 Total
1 2 0 8 2 1 0 14

{{efn|Prior to 1990, there is a likely undercount of tornadoes, particularly E/F0–1, with reports of weaker tornadoes becoming more common as population increased. A sharp increase in the annual average E/F0–1 count by approximately 200 tornadoes was noted upon the implementation of NEXRAD Doppler weather radar in 1990–1991.[10][note 3] 1974 marked the first year where significant tornado (E/F2+) counts became homogenous with contemporary values, attributed to the consistent implementation of Fujita scale assessments.[14][note 4] Numerous discrepancies on the details of tornadoes in this outbreak exist between sources. The total count of tornadoes and ratings differs from various agencies accordingly. The list below documents information from the most contemporary official sources alongside assessments from tornado historian Thomas P. Grazulis.

Color/symbol key
Color / symbol Description
Data from Grazulis 1990/1993/2001b
Data from a local National Weather Service office
Data from the 1969 Storm Data publication
Data from the NCEI database
Maximum width of tornado
± Tornado was rated below F2 intensity by Grazulis but a specific rating is unavailable.
List of confirmed tornadoes in the tornado outbreak of August 6, 1969
F# Location County / Parish State Start Coord.[note 5] Time (UTC)[note 6] Path length Width[note 7] Damage
F0 Lake Bemidji Beltrami Minnesota 47°30′N 94°51′W / 47.50°N 94.85°W / 47.50; -94.85 (Bemidji (August 6, F0)) 18:15–? 0.1 mi (0.16 km)‡ 33 yd (30 m)‡ Un­known
A short-lived waterspout was sighted.[24][7][25]
F3 NE of Nimrod to ENE of Backus Cass Minnesota 46°43′N 94°44′W / 46.72°N 94.73°W / 46.72; -94.73 (Backus (August 6, F3)) 21:20–21:40※ 18 mi (29 km)※ 200 yd (180 m)† $850,000
This intense tornado, which lifted at the southeastern corner of Big Portage Lake, significantly damaged or destroyed 13 farms to the southeast of Backus. Additionally, it destroyed 11 homes to the east of Backus. One trailer was destroyed as well. Four people were seriously injured and hospitalized.[26][8][25]
F4 NNW of Swanburg to S of Hill City Crow Wing, Cass, Aitkin Minnesota 46°47′N 94°13′W / 46.78°N 94.22°W / 46.78; -94.22 (Outing (August 6, F4)) 21:48–22:28※ 33 mi (53 km)※ ~2,640 yd (2,410 m)♯¶ $2,150,000
12+ deaths – This large, violent tornado attained a width of almost 1+12 mi (2 km; 2,640 yd; 2,414 m) while passing a short distance north of Outing. Of the dozen deaths 11 took place around Lake Roosevelt, and 40 children in the vicinity were injured while vacationing. Along its path, the tornado hurled cars and downed thousands of trees, many of which were debarked. The tornado also destroyed scores of cabins and leveled farmsteads. In all, 70 people were injured. The death toll may have exceeded 12.[9][26][27][28][29][30]
F2† NNE of Chisholm to S of Idington St. Louis Minnesota 47°36′N 92°50′W / 47.60°N 92.83°W / 47.60; -92.83 (Chisholm (August 6, F3)) 22:25–22:38※ 10.5 mi (16.9 km)※ >3,520 yd (3,220 m)♯※ $675,000
This tornado, which ended just north of Big Sandy Lake, reportedly exceeded 2 mi (3 km; 3,520 yd; 3,219 m) in width. It destroyed numerous trees, homes, and cabins. Nine people were injured.[26][6][31][30]
F2† WNW of Jacobson Aitkin Minnesota 46°54′N 93°27′W / 46.90°N 93.45°W / 46.90; -93.45 (Jacobson (August 6, F3)) 22:50–23:03※ 11 mi (18 km)※ Un­known $250,000
1 death – This tornado, which formed from the same storm as the Outing F4, destroyed a cabin, seven agricultural outbuildings, and a pair of farmhouses. The number of injuries was unknown at the time, but was later listed as three in official records. The NCEI incorrectly list the path as extending from southeast of Hill City to east-southeast of Ball Bluff.[26][32][30]
F2± WNW to NNE of Wahlsten (1st tornado)※ St. Louis Minnesota 47°44′N 92°17′W / 47.73°N 92.28°W / 47.73; -92.28 (Wahlsten #1 (August 6, F2)) 23:00–? 4 mi (6.4 km)※ 150 yd (140 m) $20,000
This tornado and the following two events occurred in close proximity and succession. Further information is lacking.[33][34][30]
F2± WNW to NNE of Wahlsten (2nd tornado)※ St. Louis Minnesota 47°46′N 92°16′W / 47.77°N 92.27°W / 47.77; -92.27 (Wahlsten #2 (August 6, F2)) 23:00–? 2 mi (3.2 km)※ 150 yd (140 m) $19,000
Details are unavailable.[33][35][30]
F2† SW of Tower to SSW of Eagles Nest St. Louis Minnesota 47°48′N 92°17′W / 47.80°N 92.28°W / 47.80; -92.28 (Tower (August 6, F3)) 23:00–? 9 mi (14 km)※ 200 yd (180 m)† $110,000
This strong tornado, which ended near Eagles Nest Lake No. 3, damaged or destroyed several homes and barns, while felling hundreds of trees.[36][37][30]
F3¶ NW of Floodwood to NW of Baden St. Louis Minnesota 46°57′N 92°59′W / 46.95°N 92.98°W / 46.95; -92.98 (Floodwood (August 6, F3)) 23:00–23:29※ 18 mi (29 km)※ 4,400 yd (4,000 m)♯※ $845,000
According to the National Weather Service (NWS), damage from this tornado was nearly as intense as that of the Outing F4, spawned by the same thunderstorm. This tornado was up to 2.5 mi (4 km; 4,400 yd; 4,023 m) wide near Floodwood. It killed 39 head of cattle, felled hundreds of trees, and destroyed several cabins and barns. 20 people were injured. The path ended north-northeast of Prosit.[36][3][38][30]
F2† SW of Eagles Nest to SSE of McComber St. Louis Minnesota 47°49′N 92°08′W / 47.82°N 92.13°W / 47.82; -92.13 (Eagles Nest (August 6, F3)) 23:15–? 5 mi (8.0 km)※ 200 yd (180 m)† $60,000
This tornado destroyed trees and cottages in its path.[36][39][30]
FU※ Bear Island Lake St. Louis Minnesota Un­known 23:30–? 0.5 mi (0.80 km) 150 yd (140 m) $10,000
This tornado is not officially listed, but was recorded in the publication Storm Data.[40][41][30]
F2± SSW of Burntside to S of Ely St. Louis Minnesota 47°52′N 91°56′W / 47.87°N 91.93°W / 47.87; -91.93 (Burntside (August 6, F2)) 23:35–? 3 mi (4.8 km)※ 193 yd (176 m)‡ $8,000
This event may have consisted of twin tornadoes that merged. Further information is unavailable. A jet-like din was noted for a few minutes.[33][42][30]
F2† N of Island Lake to NE of Two Harbors St. Louis, Lake Minnesota 47°03′N 92°09′W / 47.05°N 92.15°W / 47.05; -92.15 (Two Harbors (August 6, F3)) 23:50–00:15※ 21 mi (34 km)※ 200 yd (180 m)† $123,000
2 deaths – On the eastern shoreline of Boulder Lake, a cabin was wrecked, resulting in the deaths. Hundreds of trees were splintered and three people were injured. The tornado exhibited a skipping path, with intermittent damage.[36][43][30]
F0 NW of Monroe Platte Nebraska 41°29′N 97°35′W / 41.48°N 97.58°W / 41.48; -97.58 (Monroe (August 6, F0)) 01:40–? Un­known Un­known Un­known
A brief touchdown occurred over uninhabited countryside.[24][44][45]

See also

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Notes

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  1. ^ All losses are in 1969 USD unless otherwise noted.
  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.[5]
  3. ^ 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.[11] Most countries only recorded tornadoes that produced severe damage or loss of life.[12] 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.[13]
  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.[15][16] Tornado ratings were retroactively applied to events prior to the formal adoption of the F-scale by the National Weather Service.[17] While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007,[18] Canada used the old scale until April 1, 2013;[19] nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.[20]
  5. ^ All starting coordinates are based on the NCEI database and may not reflect contemporary analyses
  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. ^ The listed width values are primarily the average/mean width of the tornadoes, with those having known maximum widths denoted by ♯. From 1952 to 1994, reports largely list mean width whereas contemporary years list maximum width.[21] Values provided by Grazulis are the average width, with estimates being rounded down (i.e. 0.5 mi (0.80 km) is rounded down from 880 yards to 800 yards.[22][23]

References

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  1. ^ Storm Data Publication 1969, Events reported
  2. ^ Storm Data Publication 1969, Events reported
  3. ^ a b c d e f "Northwoods Tornado Outbreak August 6, 1969". NWS Weather Forecast Office Duluth, MN. Duluth, Minnesota: National Weather Service. 2019. Archived from the original on August 6, 2019. Retrieved September 11, 2019.
  4. ^ Haskins, Austin (August 6, 2019). "Tuesday marks 50th anniversary of deadliest tornado outbreak in northern Minnesota". KBJR6.com. Duluth, Minnesota: KBJR-TV. Archived from the original on August 6, 2019. Retrieved September 17, 2019.
  5. ^ Schneider, Russell S.; Brooks, Harold E.; Schaefer, Joseph T. (2004). Tornado Outbreak Day Sequences: Historic Events and Climatology (1875–2003) (PDF). 22nd Conf. Severe Local Storms. Hyannis, Massachusetts: American Meteorological Society. Retrieved September 17, 2019.
  6. ^ a b Kuehnast 1969, p. 128.
  7. ^ a b Storm Data Publication 1969, #10055652
  8. ^ a b Storm Data Publication 1969, #10055654
  9. ^ a b Grazulis 1984, p. A-80.
  10. ^ Agee and Childs 2014, p. 1496.
  11. ^ Grazulis 2001a, pp. 2514.
  12. ^ 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.
  13. ^ Cook & Schaefer 2008, p. 3135.
  14. ^ Agee and Childs 2014, pp. 1497, 1503.
  15. ^ Grazulis 1993, p. 141.
  16. ^ Grazulis 2001a, p. 131.
  17. ^ Edwards et al. 2013, p. 641–642.
  18. ^ 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.
  19. ^ "Enhanced Fujita Scale (EF-Scale)". Environment and Climate Change Canada. Environment and Climate Change Canada. June 6, 2013. Archived from the original on March 3, 2016. Retrieved February 25, 2016.
  20. ^ "The International Tornado Intensity Scale". Tornado and Storm Research Organisation. Tornado and Storm Research Organisation. 2016. Archived from the original on March 5, 2016. Retrieved February 25, 2016.
  21. ^ Agee and Childs 2014, p. 1494.
  22. ^ Brooks 2004, p. 310.
  23. ^ Grazulis 1990, p. ix.
  24. ^ a b "Severe Weather Database Files (1950-2021)". Storm Prediction Center Maps, Graphics, and Data Page. Norman, Oklahoma: Storm Prediction Center. July 11, 2021. Retrieved February 24, 2022.
  25. ^ a b USWB 1969, p. 121.
  26. ^ a b c d Grazulis 1993, p. 1106.
  27. ^ Storm Data Publication 1969, #10055655
  28. ^ Storm Data Publication 1969, #10055656
  29. ^ Storm Data Publication 1969, #10055657
  30. ^ a b c d e f g h i j k USWB 1969, p. 122.
  31. ^ Storm Data Publication 1969, #10055658
  32. ^ Storm Data Publication 1969, #10055659
  33. ^ a b c Grazulis 1993, pp. 1106–7.
  34. ^ Storm Data Publication 1969, #10055660
  35. ^ Storm Data Publication 1969, #10055661
  36. ^ a b c d Grazulis 1993, p. 1107.
  37. ^ Storm Data Publication 1969, #10055662
  38. ^ Storm Data Publication 1969, #10055663
  39. ^ Storm Data Publication 1969, #10055664
  40. ^ Kuehnast 1969, p. 129.
  41. ^ Storm Data Publication 1969, Events reported
  42. ^ Storm Data Publication 1969, #10055665
  43. ^ Storm Data Publication 1969, #10055666
  44. ^ Storm Data Publication 1969, #10067866
  45. ^ USWB 1969, p. 123.

Sources

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