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Tornado outbreak sequence of April 17–19, 1970

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Tornado outbreak sequence of April 17–19, 1970
Tornado outbreak
Tornadoes33
Maximum ratingF4 tornado
DurationApril 17–19, 1970
Overall effects
Fatalities26
Injuries222
Damage>$271⁄2 million ($215,760,000 in 2024 USD)[note 1]
Areas affectedMidwestern and Southern United States
Part of the tornadoes and tornado outbreaks of 1970

From April 17–19, 1970, a tornado outbreak occurred across parts of the Midwestern and Southern United States.[note 2] At least 33 tornadoes occurred, 17 of which were significant—F2 or greater—in intensity. April 17 produced many strong tornadoes, four  of them violent and long-lived, in New Mexico, western Texas, and the Texas Panhandle. More tornadoes hit East Texas and Oklahoma on April 18, and additional tornadoes affected the Mississippi Valley and Midwest regions on April 19.

Background

[edit]

On April 17, a number of supercells formed along a dry line northwest of the Carlsbad–Roswell area in New Mexico and tracked generally northeastward, starting around 5:00–6:00 p.m. CST (23:00–00:00 UTC). Entering West Texas, the storms interacted with a warm front and began producing violent, long-lived tornado families. The storms likely began generating large hail and weak tornadoes over rural areas in New Mexico, but encountered few structures or observers then. Ahead of the storms, dew points reached the lower 60s °F as far north as Lubbock, Texas, and slowly moved northward, in tandem with the warm front, after sunset. Along with copious moisture, strong wind shear was present at this time; these factors, as well as a robust shortwave trough, favored strong tornadoes overnight. Supercells largely paralleled the warm front all night long, coinciding with thick fog that obscured the tornadoes.[2]

Outbreak statistics

[edit]
Outbreak death toll[3]
State Total County County
total
Mississippi 4 Alcorn 4
Texas Briscoe 1
Donley 16
Hale 2
Parmer 1
Swisher 2
Totals 26
All deaths were tornado-related

Confirmed tornadoes

[edit]
Confirmed tornadoes by Fujita rating
FU F0 F1 F2 F3 F4 F5 Total
0 4 12 10 2 5 0 33

In addition to confirmed tornadoes, the following possible events were reported:

  • April 18: a possible F2 tornado hit the southern suburbs of Pampa, Texas, at 12:40 a.m. CST (06:40 UTC), unroofing or severely damaging 20 homes, destroying several trailers, and damaging municipal buildings.[4]

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.[5][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.[9][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.

April 17 event

[edit]
Confirmed tornadoes — Friday, April 17, 1970[note 5]
F#[note 4] Location County / Parish State Start Coord.[note 6] Time (UTC) Path length Width[note 7] Damage
F1 WSW of McDonald Lea NM 33°06′N 103°29′W / 33.10°N 103.48°W / 33.10; -103.48 (McDonald #1 (April 17, F1)) 00:30–? 7.1 mi (11.4 km) 33 yd (30 m) $2,500
This tornado, along with the next, may have been related to the Whiteface–Silverton F4 family. It touched down a few times, damaging chicken coops and downing utility poles.[2][19][20]
F1 N of McDonald Lea NM 33°12′N 103°19′W / 33.20°N 103.32°W / 33.20; -103.32 (McDonald #2 (April 17, F1)) 00:30–? 0.1 mi (0.16 km) 33 yd (30 m) $2,500
This tornado felled a 2+1⁄2-mile-long (4.0 km) stretch of high-tension power poles, while also damaging chicken coops and a disused house. It also rolled a few metal butane tanks and tore up 1⁄2 mi (0.80 km) of barbed-wire fence.[2][21][22]
F2 N of House to S of San Jon Quay NM 34°42′N 103°54′W / 34.70°N 103.90°W / 34.70; -103.90 (House (April 17, F2)) 02:00–? 39.8 mi (64.1 km) 50 yd (46 m) $250,000
A tornado passed through McAlister, north of Forrest, and near Glenrio, Grady, and Ragland. It damaged signage, outbuildings, a television antenna, windmills, outhouses, fences, and granaries, along with the windows and roofs of a few churches. The tornado also dislodged a garage, splintered utility poles, tore apart irrigation pipes, and drove glass 1⁄2 in (1.3 cm) deep into a pulpit and pews. Grazulis did not rate the tornado F2 or stronger.[2][23][24][25]
F4 Whiteface to Whitharral to W of Anton Cochran, Hockley TX 33°36′N 102°38′W / 33.60°N 102.63°W / 33.60; -102.63 (Whiteface (April 17, F4)) 02:50–? 30 mi (48 km) 880 yd (800 m) $2,708,000
Up to 1⁄2 mi (800 m) wide, this violent tornado—the first member of a long-tracked family—hit Whiteface, doing $20 million in damage, F4 damage to several homes, and 20 injuries. Most of the injured were in trailers, but five were in a school auditorium. Several large warehouses were leveled, their CMU foundations swept clean. Most of Whiteface was damaged or destroyed. At Whitharral the tornado destroyed a cotton gin and a sprawling grocery store. A school gym in town was destroyed just after spectators and players had left. The tornado was said to have resembled a "rain cloud" and a "'ball of fire'," attended by 4-inch-diameter (10 cm) hail and a possible pair of satellite tornadoes.[2][26][27][28][29]
F4 NE of Cotton Center to Plainview to southeastern Silverton to SW of Hedley Hale, Floyd, Swisher, Briscoe, Hall, Donley TX 34°00′N 101°59′W / 34.00°N 101.98°W / 34.00; -101.98 (Cotton Center (April 17, F4)) 04:00–06:40 96.6 mi (155.5 km) 880 yd (800 m) $7,230,000
5 deaths – See section on this tornado – 51 people were injured.
F4 Lazbuddie to southeastern Pampa to WNW of Hoover Parmer, Randall, Armstrong, Carson, Gray TX 34°23′N 102°37′W / 34.38°N 102.62°W / 34.38; -102.62 (Lazbuddie (April 17, F4)) 04:30–06:45 130 mi (210 km) 880 yd (800 m) $2,500,000
1 death – See section on this tornado – 13 people were injured.

April 18 event

[edit]
Confirmed tornadoes — Saturday, April 18, 1970[note 5]
F#[note 4] Location County / Parish State Start Coord.[note 6] Time (UTC) Path length Width[note 7] Damage
F4 W of Vigo Park to Sherwood Shores to W of McLean Swisher, Briscoe, Armstrong, Donley, Gray TX 34°39′N 101°32′W / 34.65°N 101.53°W / 34.65; -101.53 (Vigo Park (April 18, F4)) 07:00–09:15 65 mi (105 km) 880 yd (800 m) $2,100,000
16+ deaths – See section on this tornado – 42 people were injured.
F2 Lake Worth Tarrant TX 32°48′N 97°28′W / 32.80°N 97.47°W / 32.80; -97.47 (Lake Worth (April 18, F2)) 21:00–? 2 mi (3.2 km) 50 yd (46 m) $250,000
A tornado struck a marina on Lake Worth, destroying one houseboat and badly damaging two other boats. The houseboat was picked up and moved 50 ft (15 m). Four boats were sunk as well, and the marina was wrecked. Grazulis did not rate the tornado F2 or stronger.[23][30][31]
F2 W of Leon Springs Bexar TX 29°40′N 98°40′W / 29.67°N 98.67°W / 29.67; -98.67 (Leon Springs (April 18, F2)) 00:30–? 0.5 mi (0.80 km) 67 yd (61 m) $25,000
This tornado hit near Helotes, north of Cross Mountain, unroofing a few homes, downing power lines, and felling trees. It also tossed a pump house 100 yd (91 m). Grazulis did not rate the tornado F2 or stronger.[23][30][32]
F1 Plano Collin TX 33°02′N 96°41′W / 33.03°N 96.68°W / 33.03; -96.68 (Plano (April 18, F1)) 03:30–? 1 mi (1.6 km) 20 yd (18 m) $2,500
A brief tornado threw a vehicle into a fence, slightly injuring its two occupants. A rear seat was tossed over the road into another fence.[30][33]
F2 Royse City Rockwall TX 32°58′N 96°19′W / 32.97°N 96.32°W / 32.97; -96.32 ((April 18, F2)) 04:00–? 0.1 mi (0.16 km) 33 yd (30 m) $25,000
A tornado wrecked a deserted, spacious trailer, unroofed a dairy, and damaged a home. Grazulis did not rate it F2 or stronger.[23][30][34]
F0 N of Franklin Robertson TX 31°03′N 96°29′W / 31.05°N 96.48°W / 31.05; -96.48 (Franklin (April 18, F0)) 04:20–? 0.8 mi (1.3 km) 27 yd (25 m) Un­known
Only minor damage was reported.[30][35]
F0 ESE of Crossroads Lea NM 33°30′N 103°06′W / 33.50°N 103.10°W / 33.50; -103.10 (Crossroads (April 18, F0)) 22:00–? 0.1 mi (0.16 km) 33 yd (30 m) Un­known
This tornado hit northeast of Tatum, causing little or no damage. It may have occurred on April 17.[2][36][37]
F2 WSW of Ada Pontotoc OK 34°44′N 96°44′W / 34.73°N 96.73°W / 34.73; -96.73 (Ada (April 18, F2)) 22:10–? 5.2 mi (8.4 km) 50 yd (46 m) $25,000
A tornado destroyed a barn, damaged a home, and downed power lines.[4][38][39]
F0 SW of Checotah McIntosh OK 35°36′N 95°36′W / 35.60°N 95.60°W / 35.60; -95.60 (Checotah (April 18, F0)) 00:15–? 0.5 mi (0.80 km) 100 yd (91 m) Un­known
A brief tornado caused little or no damage.[38][40]

April 19 event

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Confirmed tornadoes — Sunday, April 19, 1970[note 5]
F#[note 4] Location County / Parish State Start Coord.[note 6] Time (UTC) Path length Width[note 7] Damage
F2 E of Longview Gregg 0655 1.2 miles (1.9 km)
At a nursing home, a tornado twisted a porch, resulting in roof damage. Numerous large trees were twisted off and in some cases were thrown into homes.[41] The tornado is not listed as significant by Grazulis.[42]
F3 SW of Elm Grove to S of Taylortown Caddo, Bossier 1000 6.8 miles (10.9 km)
A tornado produced a discontinuous path from Wallace Lake to near Taylortown. A mobile home was turned onto its side, and a home, tenant homes, barns, and tractor sheds sustained damage.[41] The tornado is not listed as significant by Grazulis.[42]
F2 SW of Cordova Shelby 1645 0.3 miles (0.48 km)
A brief tornado struck a golf course and a clubhouse, unroofing a large storehouse and dropping steel trusses onto the clubhouse.[41] The tornado hit north of Germantown. It is not listed as significant by Grazulis.[42]
F4 W of Ripley to Corinth to N of Counce, TN Tippah, Alcorn, Hardin (TN) 1806 47.6 miles (76.6 km)
4 deaths – A probable tornado family produced an intermittent damage path for 40 mi (64 km) across northern Mississippi. In and near Ripley, several homes sustained roof damage, windows were broken, a trailer was blown off its foundation, a barn was destroyed, and trees were uprooted.[41] A school auditorium roof was lifted and displaced slightly. Losses in Ripley reached $50,000. The tornado may have lifted and reformed into a new tornado before touching down for 3 mi (4.8 km) on the south side of Corinth.[41] The main damage was concentrated in three segments 200–250 yards (183–229 m) wide, with roof and tree damage between each segment. Three churches were destroyed, numerous homes were wrecked, and several gas leaks were reported.[41] In all, the tornado destroyed 69 homes and damaged 149 at Corinth,[41] where losses reached $1.8 million and all four deaths occurred, two of which were in a church[42] that was unroofed.[41] Across the Mississippi–Tennessee state line in Hardin County, Tennessee, a house, a mobile home, two farm buildings, and a garage sustained severe damage. Damage at Counce reached $30,000.[41]
F1 Annabella Sevier 2100 1.5 miles (2.4 km)
A brief tornado damaged two trailers and carried a woman 30 feet (10 yd). The woman sustained minor injuries to her head.[41]
F2 SW of Harrisburg Poinsett 2215 1.3 miles (2.1 km)
A church was partly unroofed and shifted on its foundation. Six trailers were severely damaged, and downed trees damaged carports, porches, and roofs.[41] The tornado is not listed as significant by Grazulis.[42]
F3 Greasy Corner St. Francis 2215 1.8 miles (2.9 km)
A small tornado touched down north of Hughes, destroying a small farmhouse and injuring two occupants. Nearby homes and other structures sustained damage.[42] The tornado is listed as an F2 by Grazulis.[42]
F1 SE of Thebes Alexander 2250 0.1 miles (0.16 km)
One unoccupied mobile home was overturned and another mobile home was shifted 1.5 feet (0.5 yd) on its foundation. Roofs were damaged and windows broken in the Olive Branch area.[41]
F0 SE of East Prairie Mississippi 2300 0.2 miles (0.32 km)
A tornado touched down at several points in the Big Oak Tree State Park, snapping trees 2.5–3.5 feet (0.8–1 m) in diameter and damaging the forest canopy.[41]
F1 Miner Scott 2330 0.2 miles (0.32 km)
A dozen trailers sustained damage in a brief touchdown.[41]
F1 Destin Okaloosa 0045 0.1 miles (0.16 km)
A small building was blown off its foundation, a boat was overturned, and there was other minor damage.[41][43][44]
F2 W of Cataula Harris 0200 0.5 miles (0.80 km)
One home was destroyed and another damaged.[42]
F1 Bloomfield Greene 0230 0.8 miles (1.3 km)
F1 SW of Bloomfield Greene 0230 0.8 miles (1.3 km)
F1 NE of Harrodsburg Monroe 0245 0.1 miles (0.16 km)
A brief tornado caused $100,000 damage to boats and a dock.[41]
F2 SW of Bloomington Monroe 0245 5.6 miles (9.0 km)
A "small" tornado struck Highland Village near Bloomington, moving one home 75 feet (25 yd), damaging several homes, overturning trailers, and damaging five planes at the county airport.[42]
F1 S of Versailles Ripley 0300 3.3 miles (5.3 km)
A three-car garage and three farm buildings were destroyed.[41]
F1 N of New Elizabethtown to NW of Hayden Jackson, Jennings 0345 12.8 miles (20.6 km)
Farm buildings were damaged.[41]

Cotton Center–Plainview–Seth Ward–Silverton–Hedley, Texas

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Cotton Center–Plainview–Seth Ward–Silverton–Hedley, Texas
Meteorological history
FormedApril 17, 1970, 11:00 p.m. CDT (UTC−05:00)
DissipatedApril 18, 1970, 1:40 a.m. CDT (UTC−05:00)
F4 tornado
on the Fujita scale
Overall effects
Fatalities5
Injuries51
Damage$7,230,000 ($56,720,000 in 2024 USD)

Related to the Whiteface–Whitharral F4, this long-tracked tornado family first damaged rural areas in the Hale Center–Cotton Center area, where two tornadoes were noted at once, 1 to 2 mi (1.6 to 3.2 km) apart, as well as four to five funnel clouds. The tornadoes damaged a 20-mile-long (32 km) swath, crushing a pickup truck and killing a few of its occupants, while destroying eight homes nearby, injuring seven people, and doing $750,000 in losses. The tornadoes also wrecked many outbuildings and barns. One of the tornadoes subsequently passed through Plainview, causing 40 injuries and $41⁄2 million in damage there. Initially seen by storm spotters southwest of town, the tornado touched down at the Plainview Country Club, skipping east as it downed power lines, trees, and some buildings. Turning northeast, the tornado intermittently damaged tall structures in a 400-to-600-yard-wide (370 to 550 m) swath through town.

The tornado produced continuous damage as it hit Seth Ward, leveling "almost everything" in a three-to-six-block-wide swath. East of Claytonville the tornado leveled a few rural homes, one of which it swept away, killing a couple inside and leaving behind some concrete blocks on its foundation. Near Claytonville, the tornado cut a continuous, 20-mile-long (32 km), 300-to-400-yard-wide (270 to 370 m) path. Rural losses reached $445,000, and 70 cattle were killed or injured. In southeastern Silverton, the tornado killed a 14-year-old girl and destroyed eight homes. Damages reached $11⁄2 million, half of which was to a large grain elevator. Two 50-foot-tall (15 m) tanks were carried 1⁄4 mi (0.40 km), and a 1,500,000-US-bushel (53,000,000 L) tank was moved 50 ft (15 m). The final damage, rated F3, occurred near Hedley as a farmhouse and barns were destroyed, resulting in a loss of $35,000. The last 22 mi (35 km) of the path may have been related to a separate member of the tornado family and included a few unrecorded injuries.[45]

Lazbuddie–Conway–Pampa–Hoover, Texas

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Lazbuddie–Conway–Pampa–Hoover, Texas
Meteorological history
FormedApril 17, 1970, 11:30 p.m. CDT (UTC−05:00)
DissipatedApril 18, 1970, 1:45 a.m. CDT (UTC−05:00)
F4 tornado
on the Fujita scale
Overall effects
Fatalities1
Injuries13
Damage$2,500,000 ($19,610,000 in 2024 USD)

This violent tornado family first hit Lazbuddie, destroying three farmhouses, killing a woman, injuring at least three people, and causing $500,000 in damage. In the area the tornado also damaged a trio of other homes and destroyed or damaged many barns and businesses. The tornado also badly damaged agricultural equipment, downed fences, and splintered power poles. Heading northeast at 40 mph (64 km/h), the tornado produced a continuous path 26 mi (42 km) long and 1⁄2 mi (0.80 km) in width before lifting and possibly reforming as a new tornado. It then redeveloped for 20 mi (32 km) between Canyon and Happy, causing a much narrower, 50-to-75-yard-wide (46 to 69 m) swath of damage. The same or another tornado reportedly produced more scattered damage near Conway.

After passing near White Deer, this or a related tornado then cut a broken, 5-to-7-mile-long (8.0 to 11.3 km), 100-yard-wide (91 m) swath across southeastern Pampa at F2 intensity, unroofing or severely damaging 20 homes and wrecking many trailers. The tornado also damaged municipal buildings in Pampa, and caused losses of $11⁄2 million there, along with 10 injuries. Its damage in town, though substantial, was spasmodic, however. The tornado finally ended in a rural area near Hoover; despite its longevity, it only produced F4 damage at the start of its trek.[46]

Tulia–Clarendon–Sherwood Shores–McLean, Texas

[edit]
Tulia–Clarendon–Sherwood Shores–McLean, Texas
Meteorological history
FormedApril 18, 1970, 2:00 a.m. CDT (UTC−05:00)
DissipatedApril 18, 1970, 4:15 a.m. CDT (UTC−05:00)
F4 tornado
on the Fujita scale
Overall effects
Fatalities16+
Injuries42
Damage$2,100,000 ($16,480,000 in 2024 USD)

The final long-tracked family of the night, this tornado was also the deadliest of the outbreak. Forming northeast of Tulia, it first caused $100,000 in damage to ranches and farms, injuring or killing 85 cattle. After impacting remote countryside for some time, the tornado then leveled a home on each side of U.S. Route 287, west-northwest of Clarendon, badly injuring a woman and killing her husband. The tornado also unroofed a third home nearby, and drove a wooden splinter into a 1.5-inch-thick (3.8 cm) metal gate frame. Next, the tornado hit the Sherwood Shores community—Howardwick today—on the Greenbelt Reservoir, destroying all but one of 173 mobile homes there. Encountering 150 people in the community, the tornado claimed at least 13 lives—a dozen of them instantly—and inflicted 35 injuries. Losses at Sherwood Shores alone reached $1.3 million, and a fourteenth death may have occurred.

Leaving the community behind, the tornado swept away a trailer on Texas State Highway 70, killing a few more people, and damaged a number of rural farmhouses. Near Interstate 40, just west of McLean, the tornado blew railroad tank cars off railroad tracks, one of which landed on I-40. The tornado later wrecked a trio of farmhouses and a cottage near McLean, while damaging five other cottages. In Gray County the tornado ravaged 60 to 75 mi (97 to 121 km) of fence and caused $400,000 in losses. It also damaged or destroyed automobiles and agricultural equipment countywide. The tornado was up to 1,300 ft (430 yd; 0.25 mi; 0.40 km) wide near McLean. The storm that produced the tornado continued into Wheeler County, where eyewitnesses reported a deluge of tornado-related debris from earlier.[47]

See also

[edit]

Notes

[edit]
  1. ^ All losses are in 1970 United States dollars 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.[1]
  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.[6] Most countries only recorded tornadoes that produced severe damage or loss of life.[7] 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.[8]
  4. ^ a b c d 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.[10][11] Tornado ratings were retroactively applied to events prior to the formal adoption of the F-scale by the National Weather Service.[12] While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007,[13] Canada used the old scale until April 1, 2013;[14] nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.[15]
  5. ^ a b c 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.
  6. ^ a b c All starting coordinates are based on the NCEI database and may not reflect contemporary analyses
  7. ^ a b c 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.[16] 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.[17][18]

References

[edit]
  1. ^ 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.
  2. ^ a b c d e f Finch, Jonathan D. (22 December 2006). "April 17 1970 Tornado Outbreak". Bangladesh and East India Tornado Prediction Site. Retrieved 22 September 2024.
  3. ^ Storm Data Publication 1970, Events reported
  4. ^ a b Grazulis 1993, p. 1111.
  5. ^ Agee and Childs 2014, p. 1496.
  6. ^ Grazulis 2001a, pp. 251–4.
  7. ^ 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.
  8. ^ Cook & Schaefer 2008, p. 3135.
  9. ^ Agee and Childs 2014, pp. 1497, 1503.
  10. ^ Grazulis 1993, p. 141.
  11. ^ Grazulis 2001a, p. 131.
  12. ^ Edwards et al. 2013, p. 641–642.
  13. ^ 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.
  14. ^ "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.
  15. ^ "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.
  16. ^ Agee and Childs 2014, p. 1494.
  17. ^ Brooks 2004, p. 310.
  18. ^ Grazulis 1990, p. ix.
  19. ^ Storm Data 1970, pp. 34, 40.
  20. ^ Storm Data Publication 1970, #10078248
  21. ^ Storm Data 1970, p. 34.
  22. ^ Storm Data Publication 1970, #10078249
  23. ^ a b c d Grazulis 1993, pp. 1110–2.
  24. ^ Storm Data 1970, pp. 34–5.
  25. ^ Storm Data Publication 1970, #10078253
  26. ^ Grazulis 1984, p. A-80.
  27. ^ Grazulis 1993, pp. 1110–1.
  28. ^ Storm Data 1970, p. 40.
  29. ^ Multiple sources:
  30. ^ a b c d e Storm Data 1970, p. 41.
  31. ^ Storm Data Publication 1970, #10134702
  32. ^ Storm Data Publication 1970, #10134923
  33. ^ Storm Data Publication 1970, #10134928
  34. ^ Storm Data Publication 1970, #10134929
  35. ^ Storm Data Publication 1970, #10134932
  36. ^ Storm Data 1970, p. 35.
  37. ^ Storm Data Publication 1970, #10078255
  38. ^ a b Storm Data 1970, p. 36.
  39. ^ Storm Data Publication 1970, #10095323
  40. ^ Storm Data Publication 1970, #10095325
  41. ^ a b c d e f g h i j k l m n o p q r Storm Data 1970.
  42. ^ a b c d e f g h i Grazulis 1993, p. 1112.
  43. ^ Grazulis, Thomas P.; Grazulis, Doris (2016). "Tornado Index # 19700419.12.20". The Tornado History Project. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. Archived from the original on 2016-03-28. Retrieved 2016-03-19.
  44. ^ "Severe Weather Database Files (1950-2021)". Storm Prediction Center Maps, Graphics, and Data Page. Norman, Oklahoma: Storm Prediction Center. July 11, 2021. Retrieved 24 February 2022.
  45. ^ Multiple sources:
  46. ^ Multiple sources:
  47. ^ Multiple sources:

Sources

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