I. Overview of the life history and extremes of the tornado
After almost a full year of calm, on the evening of December 10, CST, strings of tornado funnel clouds descended from the strong convective monomers and ran amok in ten states, including Arkansas, Missouri, Tennessee, Illinois, and Kentucky, forming the world's most powerful tornado eruption in December. According to incomplete statistics, at least 32 tornadoes appeared in this tornado outbreak, and the strong convection lasted for nearly 12 hours.
Tornado outbreak under MRMS products
Among them, the "Four State Tornado", which was grounded in Arkansas and spanned Missouri, Tennessee and Kentucky, showed a continuous four-and-a-half-hour strong rotation feature on radar monitoring, with a total path length of 386 kilometers, leveling at least 23 towns along the way. These data have completely surpassed the "Three States Tornado" of 1925, the king of tornadoes before World War II.
Strong convection monomer situation of the four-state tornado, from Jack Silin
According to photos taken by wind chasers and witnesses, combined with radar analysis, the width of the "Four States Tornado" can reach 1.6-3.2 kilometers, ranking the forefront of the global observed tornadoes - previously, the world's widest tornado was the El Reno Tornado in the United States in 2013 (4.2 kilometers) and the Funing Tornado in China in 2016 (4.1 kilometers); according to the available data, the strength of the "Four States Tornado" is likely to reach the highest EF5 level, surpassing the above tornado, and oklahoma City in 1999. Jalel in 1999, Joplin in 2011 and Moore Tornado in 2013 are equally famous.
Four-state tornadoes photographed by American netizens
The strength of the four-state tornado is first reflected in the radar data. During the tornado event, the double polarization radar 40 miles away monitored that the tornado had a radial speed of more than 100 m/s at an altitude of about 500 meters, the highest recorded since the observation of the double polarization radar; the Vrot reached 134kt around the peak of the tornado, the second in history; the debris ball raised by the tornado rose to 12,000 meters, exceeding the general cruising altitude of civil aviation aircraft.
Radar performance of the Four States Tornado, from the NWS
The strength of the four-state tornado is more reflected in its destruction. From grounding, it ignores hilly water bodies and is always strong; it blows wooden houses away completely, exposing and even part of the foundation; it carries rain and hail to wash the ground, not only peeling off the bark, but even pulling up grass and turning over the soil; it easily blows trains, blows down brick and steel concrete buildings, and even directly turns a sturdy apartment into debris - this is beyond the usual situation of tornado destruction assessments.
The surface representation of the four-state tornado comes from aerial photography
Because of this, the four-state tornado caused extremely heavy casualties, especially the workers of the Mayfield Candle Factory who were working at night, which was almost destroyed, and 12 people were killed in the town of Bremen, which had a permanent population of only 188 people, when the tornado peak passed. In addition, the other tornadoes in this outbreak are also very strong, and the tornadoes that attacked the Warehouse in Amazon, Illinois, also caused several deaths, and as of December 12, the death toll has exceeded 100.
The damage of the four-state tornado - the truck was hung from a tree
There is no doubt that the impact of the four-state tornado has surpassed the 2011 Joplin tornado, which is the most serious tornado disaster in the United States in the new century. Because of this, Kentucky has declared a state of emergency, and U.S. President Joe Biden has called it "one of the biggest tornadoes in American history."
Second, the cause of the tornado
Unlike typhoons and hurricanes, the scale of tornadoes is very small, only tens of meters to a few kilometers; the life history is very short, only ten minutes to one or two hours, and the four and a half hours of the four-state tornado is the highest in history; corresponding to the history of life, the path of tornadoes is also relatively short, generally only a few kilometers to tens of kilometers, more than 100 kilometers is very rare.
The devastation of the four-state tornado - the house was razed to the ground
The mechanism of tornado generation is also different from typhoons and hurricanes. Typhoons and hurricanes are produced in tropical or subtropical oceans, and the development mainly relies on heat and grows in a relatively positive pressure environment; while tornadoes are mainly on the land of temperate plain terrain, of course, the tropics also have them, and the development mainly depends on power, growing in a strong oblique pressure environment. In particular, the strong cold and warm confrontation environment is a hotbed created by tornadoes.
From ScottduncanWX
Before the outbreak of this tornado, there was a strong cold and warm confrontation in the central Plains of the United States: on the night of December 10, local time, the warm and humid air flowed north from the Gulf of Mexico, 850 hPa reached the intensity of the rapids, and the temperature in Louisiana, Mississippi, Tennessee and Kentucky rose to 21-24 degrees Celsius, 15-25 degrees higher; at this time, the strong cold air was moving south from Kansas, Oklahoma and other places, and the temperature difference between the north and south of the cold front was as high as 30 degrees.
From tropicaltidibits, ZH love labeling
It can be understood that although it is December, the temperature in the southeastern United States is seriously high, like late summer or early autumn; however, due to the activeness of the Arctic vortex, the cold air representing the strength of winter swoops south at a high altitude and plunges into the summer - and this winter and summer confrontation happens to occur in the great plains of the central United States, and tornadoes occur en masse.
Third, forecast and early warning situation and enlightenment to our country
Such a large-scale extreme cold and warm confrontation, of course, the US Meteorological Department has long noticed. Three days before the tornado, the U.S. Department of Meteorology issued a strong convective outlook, pointing out that there may be strong convective weather in the Central Great Plains, but did not indicate that there will be tornadoes, and then increasing the size of the next two days, pointing out that the tornado may be larger; 10 hours before the tornado outbreak, the U.S. Meteorological Department will rate medium, the first mention of the strong tornado possibility; and 8 hours before the tornado outbreak, the SPC (National Storm Prediction Center) gave a tornado watch. The area and the area of this tornado activity are roughly consistent.
The U.S. Department of Meteorology released a strong convection outlook 10 hours before the tornado outbreak
25 minutes before the tornado entered the city, the first tornado alarm (TOR) covering the city of Mayfield was released, along with the tv station to remind people to pay attention; however, the most critical tornado emergency alert (TORE) was issued more slowly, only 5 minutes before the Mayfield tornado appeared.
Four-state tornado road map, from Evan Fisher
Since the movement speed of the four-state tornado is as high as 96 km / h, the 5-minute preparation time is obviously far from enough. It can be seen that for the US meteorological department, which is the world's leading, especially the strong convection and tornado business, the early warning performance of this tornado cannot score full marks.
Meteorologists from the United States
It can be seen that extreme weather events that exceed the laws of the climate are a common problem facing the world. If the U.S. Meteorological Department had left room for extreme weather this time, after the tornado was grounded, the emergency alarm would have been sounded decisively, and the damage might not have been so large; the tornado pursuers who had been near the path of the tornado would have helped the disaster area and the victims to complete the evacuation more quickly.
China is the world's largest monsoon climate country, the main meteorological disasters are typhoons, heavy rain and drought, etc.; due to the mountainous terrain, tornadoes and other strong convection is relatively less than the United States. However, with the warming of the climate and the increase in the amplitude of the westerly wind belt, in recent years, there has been an increase in strong convective disasters in China, and the trend of replacing typhoons as the first major meteorological disasters.
Compared with the United States, China has a strong institutional advantage, can break through the extreme value in forecasting, can tolerate "ten reports and nine empty", can concentrate on disaster prevention and reduction most rapidly, and has a large number of researchers and enthusiasts who are enthusiastic about meteorological undertakings. If we continue to focus on strong convection monitoring and forecasting research, group prevention and group governance advantages, and the cultivation of social wind chasing culture, strong convection defense will certainly be able to make progress on the basis of the world's leading position, and minimize the negative impact of climate warming.