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Tornado outbreak of April 17–19, 1970
Weather event in the United States From Wikipedia, the free encyclopedia
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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. The deadliest tornado of the outbreak, a long-lived F4, killed at least 16 people in Texas, followed by another F4, also in Texas, that killed five; both belonged to tornado families. A third F4 family along the Mississippi–Tennessee state line claimed four lives as well.
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Background
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]
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Outbreak statistics
Confirmed tornadoes
Summarize
Perspective
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.[4][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.[8][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
April 18 event
April 19 event
Cotton Center–Plainview–Seth Ward–Silverton–Hedley, Texas
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.[70]
Lazbuddie–Conway–Pampa–Hoover, Texas
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.[71]
Tulia–Clarendon–Sherwood Shores–McLean, Texas
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 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 tore up 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.[72]
Ripley–Corinth, Mississippi/Counce, Tennessee
A probable tornado family produced sporadic damage for 40 mi (64 km), tracking over northern Mississippi and southern Tennessee. It did most of its damage in Mississippi, where all known deaths occurred. In and near Ripley, the tornado hit many homes, mostly damaging their roofs, and shattered windows as well, while destroying many small outbuildings. In addition, it blew a trailer off its foundation, wrecked a barn, destroyed a CMU print shop, downed trees, and slightly uplifted a school auditorium roof. Losses in the Ripley area totaled $50,000, and F2-level damage was noted.
The tornado may have lifted and reformed into a new tornado before touching down in southern Corinth, cutting a 3-mile-long (4.8 km) swath through a densely-inhabited section of town. The main damage was concentrated in three segments 200 to 250 yd (180 to 230 m) wide, with roof and tree damage between each segment. A trio of churches were destroyed, one of which was leveled, and many homes were wrecked, some incurring F4 damage. In addition, utilities were destroyed or otherwise disabled, causing gas leaks. In all, the tornado destroyed 69 homes and damaged 146 at Corinth, where losses reached $1.8 million and all four deaths occurred, a few of which were in a church that was unroofed. Additionally, the tornado destroyed or damaged eight businesses there. Across the Mississippi–Tennessee state line, in Hardin County, Tennessee, the tornado severely damaged a house, a trailer, a few agricultural outbuildings, and a garage. Damage at Counce reached $30,000.[73]
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See also
Notes
- All losses are in 1970 United States dollars unless otherwise noted.
- 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]
- 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.[5] Most countries only recorded tornadoes that produced severe damage or loss of life.[6] 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.[7]
- 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.[9][10] Tornado ratings were retroactively applied to events prior to the formal adoption of the F-scale by the National Weather Service.[11] While the Fujita scale has been superseded by the Enhanced Fujita scale in the U.S. since February 1, 2007,[12] Canada used the old scale until April 1, 2013;[13] nations elsewhere, like the United Kingdom, apply other classifications such as the TORRO scale.[14]
- 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.
- All starting coordinates are based on the NCEI database and may not reflect contemporary analyses
- 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.[15] 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.[16][17]
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References
Sources
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