Interview with tornado experts： domestic tornado research has just started, and the prediction is still in the experimental stage.

Recently, strong convective weather in Guangdong has brought heavy rain, strong winds and even tornadoes, which has attracted the attention of the outside world.

On the afternoon of April 27th, a tornado occurred in Zhong Luotan, Baiyun District, Guangzhou, causing 5 deaths, 33 injuries and 141 factory buildings damaged. At 11 o’clock on April 30, a weak tornado appeared in Qiandong Town, Raoping County, Chaozhou City, which caused some trees in the south of Raoping County to collapse and slightly damaged the workshops of individual enterprises.

The Paper noted that since April 27th, early warnings of possible tornadoes have been issued in Huangpu District and Huadu District of Guangzhou, Xinhui District of Jiangmen City, Duanzhou District, Dinghu District and Gaoyao District of Zhaoqing City. According to the early warning information previously issued by the Central Meteorological Observatory, it is estimated that there will be more than 10 thunderstorms and strong winds in parts of southern Jiangxi, southwestern Fujian, northeastern Guangxi, northern Guangdong and other places from 08: 00 on April 30 to 08: 00 on May 1, with a maximum wind force of more than 12, and there may be tornadoes.

In August 2013, the first tornado research center in China was established in Foshan City, Guangdong Province, mainly to carry out tornado monitoring and early warning tests. On April 30, 2024, Huang Xianxiang, a senior engineer at the Tornado Research Center in Foshan, was interviewed by The Paper (www.thepaper.cn). He said that the tornado in Zhong Luotan, Baiyun District, Guangzhou, caused some casualties because most of the local factories were tin houses, which had poor wind resistance. Therefore, if you encounter a tornado, you should leave as soon as possible and hide in a solid house nearby, especially a reinforced concrete house.

Huang Xianxiang said that tornadoes are very sudden and it is difficult to predict tornadoes. At present, the tornado research in China is in its infancy, and our forecasting and early warning business is still in the experimental stage. However, some features of tornado are relatively obvious, which may be monitored and identified in advance. For example, the tornado brought by typhoon Mangosteen in 2018 and the tornado brought by typhoon Siam in 2022 were all warned in advance.

Huang Xianxiang also reminded that tornadoes must be accompanied by strong convective weather. If there are many strong convective weather backgrounds, the risk of tornadoes will be greater.

[Dialogue with Huang Xianxiang]

Iron houses are weak in wind resistance and easy to collapse.

The Paper:On the afternoon of April 27th, there was a tornado in Zhong Luotan Town, Baiyun District, Guangzhou, which caused heavy casualties. What are the characteristics of this tornado? Why are the casualties more serious?

Huang Xianxiang:First of all, the intensity of this tornado is relatively strong, reaching the level of strong tornado EF 2, so the damage area caused by it is also relatively large, and more than 140 factories are damaged. The casualties were serious, mainly because the tornado was so strong that it blew down the fence and some buildings with weak wind resistance, causing casualties.

The Paper:During the tornado in Zhong Luotan, Baiyun District, Guangzhou, iron houses, trees, high-voltage lines, telephone poles and vehicles were seriously damaged, especially the iron houses, whose roofs were overturned and even their walls collapsed. Combined with the tornado disaster, what should be paid attention to in preventing tornadoes?

Huang Xianxiang:If you encounter a tornado and are in a tin factory building or some other temporary residence that is not very strong at that time, it is suggested that you leave as soon as possible and hide in a solid house nearby, especially a reinforced concrete house, while ensuring safety. Don’t be in a factory building with weak wind resistance or a long-span roof. It is safer to evacuate quickly. Because the tin factory building is easy to collapse, once it collapses, it will cause some damage. Also stay away from tall objects such as fences, telephone poles and trees.

The Paper:Before there is a tornado in a place, can you do some safety hazards investigation? What shortcomings need to be filled?

Huang Xianxiang:A prominent feature of tornadoes is strong wind, and the main safety hazards are houses with weak wind resistance, tin factories or simple fences, as well as trees, billboards and flower pots upstairs. Therefore, in addition to knowing which ones are not wind-resistant, it is also necessary to pay attention to which nearby places are wind-resistant, such as knowing where the nearest concrete building is. If necessary, you can choose to take shelter from severe weather temporarily. After all, safety comes first.

Tornado prediction is difficult, and tornado can do some early warning.

The Paper:Can tornadoes be predicted in advance?

Huang Xianxiang:Tornado prediction is more difficult, because its suddenness is particularly strong, and its scale is very small, and its local characteristics are obvious. It is not a weather system with a large influence range like a squall line, such as sweeping from east to west or from north to south. For example, in a city of several thousand square kilometers, there may be strong weather like tornado only within a few kilometers or hundreds of meters, so it is difficult to monitor the tornado and predict it, but the characteristics of tornado are relatively obvious. In some cases, some early warnings can still be made. Some weak tornado features may not be obvious, its signal itself is weak, and some features will be much weaker.

Our current early warning is mainly based on the weather radar, because the tornado storm will show some unique characteristics in the weather radar image, such as the shape of the echo, it will show a hook echo, or a notch shape, and there will be some obvious rotation characteristics. If it is a strong tornado, its characteristics will be more obvious, so we can still make some early warning. As for how long it can be advanced, according to the specific situation, not every tornado process is the same, and some of them develop very fast, which may suddenly strengthen and suddenly occur. This kind of predicted time may not be advanced, and it may not be seen until a tornado occurs. Or some may only have a few minutes to give early warning. However, if it is a tornado with a long path or not so sudden, we can pay attention to its characteristics earlier. On September 17, 2018, a tornado circulating around the typhoon Mangosteen occurred in Foshan. We paid attention to this situation early, and made an early warning, with an advance of more than 30 minutes, but not every tornado has strong stability or obvious characteristics. Some of them developed too fast and may be displayed on the radar. The last graph is strengthened, and the next graph is weakened, but the tornado may happen during the period of strengthening and weakening, but we can’t see the data during this period, because our data is updated every 6 minutes, and it may happen during this interval, so it is very difficult to warn.

The Paper:Is the information you said that you watch every 6 minutes the information of weather radar?

Huang Xianxiang:Yes, every 6 minutes, the S-band weather radar will produce a scanned image, but now we have set up some small X-band radars, and we can have a picture in about 1 minute, and the echo structure we see will be more detailed. However, the small radar has a weakness, and the echo signal decays very quickly, so many times we can’t see some weather conditions.

The Paper:You mentioned the prediction of weak tornadoes and strong tornadoes earlier, and the signals may be different. How is this weak and strong?

Huang Xianxiang:In fact, it is difficult to monitor the tornado itself, and the intensity of the tornado can only be determined by the damage degree of the disaster on the spot. Why did the tornado in Guangzhou become a tornado this time? This is also determined according to the degree of damage at the scene, for example, a large area of factory buildings was damaged. In the determination process, we also need to look at the quality of the factory building, whether it is a concrete structure or a simple iron factory building. For example, in the disaster-stricken area of Zhong Luotan tornado in Baiyun District, Guangzhou, most of the factories are brick-concrete structures. Based on these factors, we evaluated them as EF 2. We have a measurement standard with different indexes. If the factory building with reinforced concrete structure is razed to the ground, the strength will be greater, maybe EF 4 strength is even stronger. According to the damage degree caused by the tornado scene, its strength is determined. If only some trees are broken, it is the weakest grade of EF1 or EF 0, so the strength is determined according to the damage degree.

The Paper:For this tornado in Zhong Luotan Town, Baiyun District, Guangzhou, what signs did it have before?

Huang Xianxiang:In radar images, there are some echo features of tornadoes, such as hook echo structure and rotation.

The Paper:From the meteorological point of view, the tornado in Zhong Luotan is a tornado. Is it a tornado that can be predicted in advance?

Huang Xianxiang:The characteristics of tornado may be more obvious before and after the occurrence, so its advance will not be very long, and it may take a few minutes at most.

The Paper:We noticed that on the afternoon of April 27th, before the tornado occurred in Zhong Luotan, Baiyun District, Guangzhou, there might be a tornado warning in Huadu District, Guangzhou, but there was no tornado warning in Baiyun District. Is this because it is difficult to predict the tornado accurately at present?

Huang Xianxiang:Tornado warning itself is full of challenges. It is understood that at that time, Baiyun District issued a high-level orange warning signal for thunderstorm and gale and an orange warning signal for hail to remind the public to guard against extreme gale and hail weather.

Domestic tornado research is still in its infancy.

The Paper:What is the current level of tornado prediction and research in China?

Huang Xianxiang:At present, the tornado warning business in many places is still in the experimental stage, because this work is full of challenges. The United States has established an advanced tornado warning and forecasting business, because there are high frequency tornadoes there, and there are more than 1000 tornadoes every year, and they have studied tornadoes for more than half a century, and our research is still in its infancy.

The Paper:Typhoon seems to have a path. Is the path of tornado clear?

Huang Xianxiang:Because typhoon is a weather scale system with a diameter of hundreds to thousands of kilometers, its typhoon cloud system can be seen on the satellite cloud picture, and even the typhoon eye area can be clearly distinguished. Combined with a variety of observation data, the typhoon center can be located and the moving path of the typhoon can be given.

Tornado is a small-scale vortex system extending from thunderstorm clouds, which is small in scope, fast in birth and disappearance, and often dissipates due to the friction of the underlying surface during the moving process, so the path of tornado often jumps, which is difficult to identify from the weather radar. We need to give the moving path of tornado mother storm through weather radar, then find out the possible whereabouts of tornado according to the characteristics and reporting information of mother storm, and then carry out on-site aerial photography and disaster adjustment of tornado damaged area to draw the approximate path of tornado.

The Paper:What is the early warning situation of tornadoes in Guangdong in recent years?

Huang Xianxiang:In recent years, by studying the weather characteristics of historical tornadoes in Guangdong, the early warning technical indicators of tornadoes in Guangdong have been preliminarily summarized. In the early warning practice, in addition to predicting the tornado in the circulation of Typhoon Mangosteen in 2018, the tornado brought by Typhoon Siam in 2022 was also warned in advance.

The Paper:Is it difficult to predict other tornadoes?

Huang Xianxiang:Right. Because some features burst too fast, suddenly occur, and suddenly weaken, they may just be seen and disappear in the radar image the next second. Sometimes it is discovered after receiving the report that such weak features can also produce tornadoes; Sometimes early warning of tornadoes with strong signal characteristics may not produce tornadoes in the end, but only local strong winds.

The Paper:Will the warning range of tornado be larger than the actual range?

Huang Xianxiang:The United States is the country with the highest level of tornado warning, and so far the warning range of tornadoes in the United States is often larger than the actual impact range. Our current practice is similar, mainly based on weather radar combined with automatic weather stations to comprehensively judge the dynamic evolution trend of tornado mother storm, so the early warning range may be larger than the actual range. However, it also depends on the specific situation. It is also possible that the activities of tornadoes exceed the warning range, and the actual impact range needs to be evaluated according to the moving path and damage range of tornadoes.

There are many strong convective weather, and the risk of tornado may be higher.

The Paper:In recent years, extreme weather has occurred frequently, which has also caused disasters in some places. This round of heavy rain in Guangdong, strong convective weather, rainfall in many places broke the extreme value of accumulated rainfall in April. Will this strong convective weather and extreme climate lead to more tornadoes?

Huang Xianxiang:Tornado itself belongs to the most extreme and intense kind of severe convective weather. In other words, strong convective weather may not necessarily produce tornadoes, but tornadoes must be accompanied by strong convective weather. If there are many strong convective weather backgrounds, the risk of tornado is higher.

In addition to the strong convective weather background, the tornado is also related to some atmospheric conditions. For example, in addition to the intersection of cold and warm air currents, sufficient energy and water vapor transportation, it is also required that there is a strong wind in the middle and low altitude, which is what we usually call a "jet stream" to form a strong vertical wind shear, which is conducive to the occurrence of tornadoes. In addition, it depends on whether the geographical location and terrain conditions are suitable for the formation of tornadoes. For example, the possibility of tornadoes in mountainous areas is relatively small, because tornadoes often occur in flat plains, and mountainous areas will weaken the occurrence and development of tornadoes.

The Paper:Under the background of frequent extreme weather, will tornadoes present new features and changes?

Huang Xianxiang:It is not that tornadoes will produce new changes. Maybe the weather will be extreme in one year, and the number of tornadoes will increase this year, but it is also possible that tornadoes will rarely appear next year. It can only be said that there is a certain correlation between the occurrence of tornadoes and abnormal weather, but it is difficult to sum up a long-term and trending change feature from it, which needs more information for further study. It is not possible to draw a new change and new feature of a tornado from the phenomenon of a certain year, but it takes a period of time to analyze the phenomenon and get the result.

The Paper:According to the forecast of meteorological department, from April 30th to May 1st, there will be thunderstorms and strong winds, and there may be tornadoes in some areas such as southern Jiangxi, southwestern Fujian, northeastern Guangxi and northern Guangdong. Can the tornado situation behind be predicted or analyzed?

Huang Xianxiang:Because the weather situation is very unstable these days, due to the combined effects of cold air and high-altitude trough, there may be thunderstorms, strong winds, hail and heavy precipitation, and the possibility of local tornadoes is not ruled out. For example, on the morning of April 30th, a tornado happened in Chaozhou, East Guangdong.

The Paper:Is it possible for a tornado to happen in a crowded place in the city center? Why?

Huang Xianxiang:Tornadoes are easy to occur in open and flat areas, and hilly, mountainous and tall buildings are not conducive to the development of tornadoes. There are generally high-rise buildings in the city center, which is not conducive to the occurrence and development of tornadoes. Of course, it is not excluded that some rare tornadoes occur in cities, but most tornadoes still occur in open areas. Moreover, most buildings in cities are reinforced concrete structures, which are relatively strong and safe. The probability of tornado itself is not high, and the probability in the central city is even lower. Therefore, the residents in the city need not worry too much, and they can feel more at ease by mastering certain knowledge of natural disasters such as strong winds.

The Paper:What should the public pay attention to when facing tornadoes?

Huang Xianxiang:If you are at home, stay away from doors, windows and external walls of houses and hide in the room opposite to the tornado. If there is a basement or semi-basement, it will be safer to hide there.

If you are in a temporary shed or tin house, you should leave as soon as possible and look for a solid house to escape.

If you are in the wild, you should find a low-lying area as soon as possible, hold your head down to avoid it, and stay away from trees, billboards, fences, etc. to avoid being injured by them.

If you are in a car, when the distance is far away, you should drive to the place opposite to the tornado route as soon as possible; When you are too close to escape, you should leave the car as soon as possible, look for low-lying areas, and hold your head down to avoid. Because the intensity of the tornado can roll the car into the sky, the car is not a safe zone.