This summer, a super typhoon made many people dizzy. The 9th super typhoon of this year, "Meihua", wandered around the sea for 11 days, from east to west, fooling people from Fujian to northeast, and then landed in North Korea only with the strength of tropical storm. Its complicated path changes have left many meteorologists in a dilemma, and also made the protective net erected in the eastern coastal areas of China empty. However, among the numerous tropical cyclones that have occurred in the northwest Pacific Ocean and the South China Sea, it is far from the most complex one, and even does not rank among the top ten. Among the typhoons that have affected China in recent years, there are three wonderful flowers: Wayne in 1986, Nader in 1991 and Lily in 2001. These three typhoons were once called "three strange typhoons in Taiwan's typhoon history" by Taiwan's "Central Meteorological Bureau". The weather view in this issue takes you closer to the "three strange platforms" and reveals the complex causes behind their tangled paths. 
Meteorological Science Popularization Disaster Prevention and Reduction Series - Typhoon The 9th super typhoon "Meihua" in 2011
Track and speed of typhoon Dual typhoon effect makes the path drift
"Wayne" - the first of the "three strange platforms"
In the eyes of many meteorologists, the No. 16 typhoon "Wayne" in 1986 is undoubtedly the best example of the changeable track of typhoons in the South China Sea. After the formation of the northern part of the South China Sea, it first made a circle counterclockwise, and then headed straight to Guangdong in the northwest direction. When it was close to Guangdong, it suddenly turned around, followed the coast of South China to the west of Taiwan, landed, and then crossed Taiwan obliquely from the east into the sea. After turning a head in the sea, it crossed the Bashi Strait and returned to the South China Sea. After the South China Sea has traveled one circle clockwise and one circle anticlockwise, it suddenly accelerates to land on the Leizhou Peninsula, then passes through the Beibu Gulf, and dissipates after moving close to northern Myanmar. This strange typhoon was active in the north of the South China Sea and the west of the Philippine Sea when it existed, with a life span of 20 days. It is currently one of the longest lived typhoons in the Western Pacific Ocean. It was also the first typhoon to land from the middle of the west coast of Taiwan, and set a new record of instantaneous maximum gust (68 m/s) in Penghu Bay. What's more strange is that after landing in Taiwan, it once weakened to a tropical depression, then "came back from the dead", and developed again to the typhoon level. Access details 
Nader and Lily: Wonderful Flower in Typhoon
The 19th typhoon "Nader" in 1991 is also a wonderful flower among typhoons. Its path is erratic, including four big turns, two enhancements, and two landings in China within 17 days. After forming on the surface of the northwest Pacific Ocean, "Nader" went westward into the South China Sea, but suddenly turned around and drove back to the Pacific Ocean, and then turned back straight to Taiwan. After landing in the south of Taiwan, it continued to approach the border between Guangdong and Fujian, turned south when it was close to the coast, rode a long distance and returned along the path close to the original path, finally landed near Shantou, and then gradually dissipated due to topographic factors. During the period from the beginning of the generation of "Lily" to its landing in Taiwan, its path could hardly be seen clearly. After three sharp turns, Okinawa blew through Taiwan from northeast to southwest. On Taiwan Island, it once weakened to a tropical depression, and then "revived" again after entering the South China Sea, and gradually dissipated after landing near Shantou. Access details
What causes the exception path?
Such a type of typhoon, their travel mode is called abnormal path. Li Xiaoquan, chief meteorologist of China Weather Network and former head of the Central Meteorological Observatory, said that the abnormal path in meteorology means that some tropical cyclones have irregular changes such as rotation and stagnation due to the complex and changeable peripheral guiding air flow or other factors. The movement of tropical cyclones is affected by the guiding airflow. The guiding air flow is mainly composed of the flow field in the large-scale weather system around the tropical cyclone, which includes the subtropical high (subtropical high for short), the large-scale trough or ridge of the mid high latitude westerlies, etc. Among them, the airflow around the subtropical high is one of the most important factors. In general, if the sub high strength and stability at sea, the tropical cyclone will also move along the normal path. However, when the environmental flow field is in adjustment and change, or when multiple typhoons occur at the same time, the shape and intensity of the subtropical high will change greatly. Under its influence, the path of tropical cyclone will become abnormal. Access details 
Fujiwara effect that cannot be ignored
In addition to the adjustment of the weather system, other typhoons existing nearby also have a considerable impact on the change of the path. In the weird path of the "Three Strange Terraces", there are "contributions" from other typhoons in the same period. Nader was affected by two tropical cyclones successively. At the beginning of its generation, due to the strong peripheral circulation of tropical storm "Luca" in the east and being too close to the land, "Nader" strengthened very slowly. After Luke left, due to the adjustment of the circulation situation, the guiding current changed, and "Nader", who had entered the South China Sea, turned again into the Luzon Strait. Later, it landed on the Hengchun Peninsula at the southern end of Taiwan and weakened rapidly. In addition to the mountains in Taiwan, the main reason for its weakening was that the typhoon "Merry", which was located in the southeast of "Nader" at that time, was gradually approaching, and its surrounding circulation wind field was inconsistent, which increased friction, which was also one of the reasons. After landing, "Nader" turned 90 ° and began to move southward due to the traction of Meili and the southward movement of the high pressure. Access details
Why do they all appear in autumn?
"Nader" and "Lily" were both born in autumn, and "Wayne"'s life span was also in late summer and early autumn. According to Xu Yinglong, a typhoon expert from the Central Meteorological Observatory, typhoons in autumn are prone to variable paths and intensities. The meteorological factors affecting typhoons off the coast of China are mainly the weather system of the westerlies, the subtropical high, the equatorial convergence zone and other weather systems. In the autumn, these forces are in a state of game, unable to distinguish between obvious winners and losers. All forces do not occupy a strong position, so the typhoon is more affected by various factors, and its movement path and intensity are also easy to change. Especially after entering the South China Sea, the complex terrain will make the path and intensity changes of autumn typhoons more complex. Access details 
epilogue
Therefore, when there are multiple tropical cyclones on the same ocean surface, coupled with the complex circulation situation, path prediction will become very difficult. This is why Taiwan, which is experienced in defending Taiwan, almost collapsed in the face of "Lily". Chen Lianshou, the academic leader of typhoon scientific research in China, once said that the most serious forecast error of tropical cyclone is often caused by the sudden change of moving path. It is urgent to strengthen the research on the sudden change of tropical cyclone movement.
