Tornado Outbreak Sequence Of May 2019

The tornado outbreak sequence of May 2019 was a prolonged series of destructive tornadoes and tornado outbreaks affecting the United States over the course of nearly two weeks, producing a total of 400 tornadoes, including 53 significant events (EF2+). Eighteen of these were EF3 tornadoes, spanning over multiple states, including Nebraska, Kansas, Texas, Missouri, Oklahoma, Indiana, Iowa, and Ohio, with additional tornadoes confirmed across a region extending from California to New Jersey. Two EF4 tornadoes occurred, one in Dayton, Ohio, and the other in Linwood, Kansas. Four tornadoes during this outbreak were fatal, causing a total of eight fatalities. The deadliest of these occurred on May 22 near Golden City, Missouri, where an EF3 tornado took three lives, including an elderly couple in their eighties. The damaging series of tornadoes that occurred in Indiana and Ohio on the evening of May 27 during this event is sometimes locally referred to as the Memorial Day tornado outbreak of 2019, which became the 4th costliest weather event in Ohio history.

Overview

The final confirmed tornado total from this highly prolific outbreak sequence was 400, including 51 strong tornadoes and two violent tornadoes. Tornadoes were confirmed in 23 different states. On May 29, the U.S. had its 13th straight day with at least eight tornadoes, which broke the previous record of 11 days straight set in 1980. On the day when the record was broken, the U.S. had an average of 27.5 tornadoes per day during the outbreak. Only three days during this period did not see an EF3 tornado or stronger. An additional two tornadoes were also reported on May 30, after the streak officially ended.

While numerous tornadoes were confirmed in tornado-prone areas, other tornadoes touched down in areas well outside of these regions, including confirmed touchdowns in California, Oregon, Idaho, Nevada, Arizona, and New Jersey. By May 24, the state of Pennsylvania had already exceeded its yearly average number of tornadoes.

The thunderstorms associated with this outbreak sequence also produced frequent heavy rainfall, sometimes at record levels, on previously-saturated ground across the U.S. and eastern Canada. This resulted in widespread river and lakeshore flooding and flash flooding, which frequently interfered with emergency crews responding to tornado damage, and also interfered with National Weather Service damage surveys. The new precipitation also extended existing flooding along the Mississippi River system to record durations.

The May 2019 outbreak sequence is remarkable for its unusually low casualty rate relative to the number and intensity of tornadoes. Neither of the EF4 tornadoes in this outbreak resulted in a single death, in spite of one tornado being rain-wrapped, never clearly visible, and nearly a mile wide, and the other tornado striking a densely-populated urban area at night. A seamless forecasting system with nearly 30 minutes of lead time is credited for preventing deaths in these two cases.

Meteorological synopsis

May 17

The threat for organized severe weather on May 17 was first outlined five days prior, when the Storm Prediction Center (SPC) outlined the Texas and Oklahoma panhandles, as well as western Kansas, in a 15% probability contour. On the morning of May 14, this risk area was expanded and 30% severe probabilities were introduced as the SPC gained confidence in a widespread and prolonged severe weather outbreak. For the first time in the organization's history, a threat of severe weather was introduced for their entire day 4–8 period. By May 17, a dual enhanced risk existed across the Central Plains, one across much of Nebraska and the second across southwestern Texas. As a large scale upper-level trough ejected into the region, dew points in the low to mid-60s °F surged north in front of a dryline. A cap across the region allowed the atmosphere to become extremely unstable, while an eastward-moving dryline was expected to become the focus for severe thunderstorms later in the day. The SPC noted uncertainty regarding convective development farther south across southwestern Kansas into Oklahoma but mentioned that any thunderstorms would be capable of significant severe weather if they came to fruition.

By late afternoon, several discrete supercell thunderstorms formed across northwestern Kansas and progressed into western and central Nebraska. While weak and largely uniform wind shear caused several splitting storms that destructively interfered with one another, one supercell later in the evening formed within a strongly sheared environment, becoming intense and long-lived as it progressed northeastward. It produced seven tornadoes in total, five of which were weak. One EF2 tornado near McCook caused major damage to a house, outbuildings, and trees, while another EF2 northeast of Stockville rolled hay bales and snapped twelve power poles. The strongest was an EF3 that extensively damaged or destroyed well-built structures at a farmstead near Stockville. Later in the evening, another long-lived supercell formed in southwestern Kansas where SPC had previously highlighted uncertainty in convective development. This supercell produced four tornadoes in areas southeast of Dodge City, including an EF3 and two EF2s. The EF3 tornado caused severe damage to farmsteads near the towns of Minneola and Bloom, and one of the EF2s touched down in the town of Lewis, causing damage there before striking several farmsteads. A total of 21 tornadoes were confirmed.

May 18–19

Into the morning hours of May 18, the large scale upper-level trough continued to shift eastward. Strong mid- and upper-level winds associated with this feature spread across much of Oklahoma and Texas, accompanied by dewpoints in the upper 60s to lower 70s °F and mid-level CAPE values on the order of 2,500–3,500 J/kg. While the prominent threat was expected to be damaging winds along an eastward-moving mesoscale convective system, the SPC noted the potential for embedded and brief tornadoes. Throughout the pre-dawn and early morning hours, a mixture of semi-discrete and linear thunderstorms developed across central and eastern Oklahoma down into northern Texas. Strong southeasterly surface winds ahead of this convection in Texas provided the impetus for prolific tornado production over subsequent hours as it moved toward the northeast. A long-lived supercell produced seven strong tornadoes as it progressed from near San Angelo, Texas, to northwest of Coleman. Three of these tornadoes reached EF3 intensity, including a large multiple-vortex tornado that struck Ballinger, where homes were left with only interior rooms standing, and a water tower was punctured by flying debris. The cities of San Angelo and Abilene both sustained direct hits from EF2 tornadoes, resulting in severe damage to many homes and businesses. Farther to the north, a brief but strong tornado occurred east of Geronimo, Oklahoma, ripping the roofs and exterior walls off of two homes and injuring one individual. Through the late morning and afternoon hours, a squall line progressed across eastern Oklahoma and northwestern Arkansas. In the presence of strong instability and very strong low-level shear, numerous tornadoes were confirmed across the region, all rated EF0 or EF1. Fort Smith, Arkansas sustained considerable damage from two separate EF1 tornadoes. Widespread damaging winds were also observed, reaching 100 mph (155 km/h) in some places.

By the early morning hours of May 19, the squall line that had developed the previous day was pushing through Louisiana, resulting in numerous embedded EF0 and EF1 tornadoes. The strongest of these tornadoes was a high-end EF1 that passed near Mamou

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