1984 Soviet Union tornado outbreak

The 1984 Soviet Union tornado outbreak, also known as the 1984 Ivanovo tornado outbreak, occurred on June 9, that struck the Ivanovo and Yaroslavl regions north of Moscow, an area over 400,000 km2. At least two of the eleven known tornadoes were violent events, equal to F4 or higher in intensity on the Fujita scale. It was one of only three disastrous tornado outbreaks (one of the others being the 1904 Moscow tornado) in modern Russian history, and the third-deadliest tornado outbreak in European history.

Based upon observed damages, the main tornado, an F4 in Ivanovo caused extreme damage, throwing heavy objects of 50000 kg for distances up to 200 m. Another tornado, assessed to have been at least F4, occurred at Kostroma. Severe thunderstorms also produced hail up to 1 kg in weight, among the heaviest hailstones confirmed worldwide. In all, the entire tornado outbreak killed at least 69 people (though the exact death toll is unknown) and injured 804. It was previously rated as an F5, however, recent reanalysis has lowered the rating to F4 in 2018 by the European Severe Storms Laboratory.

Meteorological synopsis
On June 8, 1984, a negatively tilted trough caused an extratropical low pressure area to form over the coast of the Socialist Republic of Romania (now non-Communist Romania). Surface moisture moved north from the Black Sea and caused nearby dew points to rise to 20 C; though at that time these were restricted to Romania and the Ukrainian SSR, dew points were higher than average elsewhere. By 1800 UTC, developing thunderstorms over the Ukrainian SSR spread overnight into the Russian SFSR. Between 00 and 12 UTC on June 9, the strengthening low pressure area moved north-northeast over the northwestern Russian SFSR before undergoing occlusion. In the meantime, a strong cold front rapidly advanced along a line extending south from the surface low, then south of Minsk in the Byelorussian SSR (now Belarus), to near Bucharest. This front separated the drier air mass to the north from the warm, moist air mass near the Black Sea, and strong wind speeds near ground level caused vertical mixing. Therefore, dew points actually dropped before the first tornadoes formed, but nevertheless several factors overcame the lower dew points to produce tornadoes. Among these were a strong upper-level jet stream, clear skies causing daytime heating and instability, strong synoptic-scale lifting leading to ascension of updrafts, and high adiabatic lapse rates promoting thunderstorm development. All these factors combined to produce severe weather near Moscow. The tornadoes occurred in this region because an unstable and moist air mass, supported by warm sea surface temperatures over the Black Sea, had been in place four days before the outbreak began. The unusually strong intensity of the trough in the region on June 8–9, with a 500-millibar geopotential height measured at about 2.7 standard deviations below normal, also favored an intense tornado outbreak.

Ivanovo/Lunyovo
A large, long-tracked, and devastating tornado, considered one of the worst in Russian history, destroyed numerous towns and villages along its path. Rated F4 on the Fujita scale, the 1130 metres tornado killed at least 69 people and injured more than 130 others. About 1,180 homes were also damaged, destroyed or leveled by the tornado. Some estimates indicate up to 95 deaths or even more, with some sources suggesting 400 deaths in the outbreak were all related to the Ivanovo tornado.

At 1130 UTC —other sources say 1205 UTC —this powerful multiple vortex tornado touched down 15 mi south of Ivanovo. Near Ivanovo, the tornado snapped or bent pine, spruce, and birch trees about 1 – from ground level. In the town itself, the tornado picked up and cast aside a crane, weighing 320000 kg, and threw a water tank, weighing 50,000 kg, over a distance of 200 m. ESWD mentions that the tornado destroyed factory areas.

Near the Volga River, the tornado ripped up trees by their roots and destroyed many small huts. Steel water containers capable of holding 150 m3 of water were carried 100 m in the air and transported 1 km from their original site. Hail in association with the parent thunderstorm weighed up to 1 kg, among the heaviest hailstones measured anywhere in the world; though the measurement came with few details, it is comparable to the world record, a hailstone also measuring 1 kg in Bangladesh on April 15, 1986. The F4 tornado tracked for 99 mi—though some sources suggest only 80 km —before dissipating near Lunyovo in Yaroslavl Oblast. It caused at least 92 deaths, though many others likely went unreported.

Kostroma/Lyubim
According to Russian researchers writing in the 1980s, this tornado was either the same as the Ivanovo tornado or a member of the Ivanovo tornado family; if the latter, it may indicate that the Ivanovo tornado was in fact two separate tornadoes spawned by the same thunderstorm. However, recent research indicates that the Ivanovo storm was not the same as the one that produced the Kostroma tornado. Numerous trees were thrown long distances by the tornado. A crane weighing 350 tonne was knocked over, and numerous other structures were damaged. The severity of the damage was rated F4; however, there are indications that the tornado may have attained F5 intensity.