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Yangcheng Evening News reporter Yan Ying U.S. tornadoes occur every year, especially in April, for the most, but this year was particularly frequent occurrence. According to the meteorological data in at 8:00 on April 27 at 8:00 on the 28th to the 24-hour period, a tornado swept through the southeastern United States and several southern states, the number reached a record 312 games, far more than 148 games 24 hours before record. In the hurricane, at least 350 people were killed and thousands injured. In the previous afternoon of April 17, Foshan, Guangdong, there have been tornadoes in some areas, causing serious casualties and property loss. A tornado is formed? Why are similar latitude with China, the United States more frequent tornadoes occur? Tornado why so much power, its early warning and the difficulties? Guangdong Provincial Meteorological Station chief forecaster for Ng Chi-wo’s long-term study of heavy rain and severe convective weather, the Yangcheng Evening News reporter asked him to answer this series of questions. Tornado’s maximum wind power up to 300 m / s CLC Ng Chi-wo, a tornado is very unstable weather in the strong convection due to air movement generated a strong air vortex, generated from the parent thunderstorm, normally air vortex formation middle in the air. Since then, the vortex to move upwards, the upper part is a thick black or gray cumulonimbus, Genting higher, stronger convection, mature vortex downward, drooping like the same trunk. Fortunately, not landing, after landing on the formation of tornadoes, will rotate the object on the ground, inhalation of air, causing great harm. Tornado-prone areas of Guangdong, as thunderstorms also produced from the parent thunderstorm. And it’s the biggest difference with thunderstorms and strong winds, is a vortex, resulting in rotation. Therefore, a tornado appears, often accompanied with high-speed rotating funnel cloud column, and generally associated with thunderstorms, sometimes accompanied by hail. Impact of a single tornado on the ground are not widespread, affecting areas from a few meters to several hundred meters in diameter, but the maximum wind speed near its center up to 300 m / s, the typhoon center is much larger than the maximum wind speed, so devastating. Fang Ng Chi-wo said, the reason why a tornado caused a huge disaster, partly because it is a great wind to generate great force, and partly because of its central pressure is very low, will the ground and spinning things and attracted to the high-altitude air, and it is siphoning off the ground, moving objects, people and things spinning in the rotation may also be left out from the air, with heavy losses. Tornado formation of warm and cold air is easy to stack in the United States Although the United States and China are similar latitude, but the occurrence of tornadoes in the United States far exceeds the frequency and lethality of China, as well as Why tornado special Side said Ng Chi-wo, the occurrence of a tornado must meet certain favorable conditions, including the need to accumulate enough moisture,wow gold, and when cold and warm air movement leads to repression of unstable energy release, also requires a vertical direction of a strong change in wind direction and wind speed , meteorology is called In addition, the weather warm and cold interface-based system is needed to trigger the formation of tornadoes mechanism. The United States location, topographical features and the climate system is conducive to the generation of these conditions. Can be seen from the map, the United States east Atlantic, west Pacific, the Gulf of Mexico south of there. Because the United States primarily in the mid-latitude, under the control of the subtropical high from the sea three warm air can be continuously transported to the continental United States. A lot of water vapor along the three sides from the lower atmosphere to the U.S. mainland, and from the top of the Rocky Mountains in the central plains region of dry air overlay, it is easy to produce vertical movement of air column, resulting in the emergence of a tornado. In addition, the United States and more plain, relatively flat terrain, but also conducive to tornado formation and development. According to statistics, more than 50 years ago the number of tornadoes increased by at least 35 times. Some scientists believe that with the increase in the number of cars on the road has a close relationship. American highways are now often run on less than two million cars, trucks, more than 60 million. When high-speed operation of the two cars the wrong car, the air will form a counterclockwise vortex. Millions of cars produced by the air vortex together, and will form a powerful vortex. This strong vortex in the event of favorable weather systems and atmosphere temperature and humidity conditions will cause a tornado. The average tornado warning 18 minutes ahead of forecast U.S. tornado warning has been forecast that 50-year history, the highest level of research in the world. Strong, director of the Central Meteorological Station forecast Zhou Qingliang a recent interview, the current U.S. tornado warning has two levels, one at the national level early warning center, similar to China’s Central Meteorological Station, released 1-8 days warning in advance 8 days to forecast where tornadoes may occur. Second, all regions of the United States about a hundred units responsible for local forecasts, will be released once the monitor to a tornado warning. Even so, an accurate prediction of the tornado is still very difficult. Fang Ng Chi-wo said, limited technology and the level of awareness, and not before a tornado forecast was for a long time. In this regard because tornadoes are strong convective weather,cheap wow gold, its emergence and rapid development of mobile is also very fast,wow po, resulting in more difficult to predict; the other hand, although the U.S. has already established a dense network of radar surveillance, but the resolution is still a tornado 1 km. The tornado is often small-scale vortex, the impact on the ground of a single tornado, the average diameter of only 250 meters, is not easy to identify. So now, the United States early warning of tornadoes, the average time is 18-19 minutes. With a top speed of more than 300 kilometers, a tornado moving fast, to avoid the limited time left to the people. Tornado disaster in the United States, there are victims is not just a few minutes the radio to hear alarms, tornado found around the immediate concern. Guangdong to thunderstorms and severe convective weather, the main tornado is not a multiple radar blind spot compared with the United States, China is not high occurrence of tornadoes, severe convective weather in Guangdong province is the most thunderstorms, accounting for the more than 50%, while only a few percent the proportion of a tornado. Is also a strong convective weather, thunderstorms and tornadoes The main difference is that there is no formation of rotation. CLC Ng Chi-wo, thunderstorms is in the event of thunder, rain and weather phenomena, wind up, or more than eight (≥ 17.2 m / s) of the weather phenomenon. Because thunderstorms mainly by the formation of a strong downdraft, when the mine reaches a certain level cumulus cloud in the water droplets to the ground suddenly Zala, will bring strong winds and even hail. From the wind speed and wind strength, the tornado to more than thunderstorms, destructive power is greater. For the monitoring of severe convective weather, Guangdong Province, is the first batch of one of the provinces with a Doppler radar, began in 2000. At present, China and the United States similar to the Doppler resolution, 1 km, the province currently has nine Doppler radars were installed, are located in Zhanjiang, Yangjiang, Shenzhen, Shantou, Shanwei, Guangzhou, Heyuan, Meizhou and Shaoguan . From the density of point of view, it is almost the level of the U.S. radar network. But Fang said Ng Chi-wo, the monitoring of severe convective weather also affected the level of technical and cognitive limitations. If the province is responsible for monitoring the station density is not big enough, 200 km before a space station, and observed twice a day only, on the rapidly changing convective weather during the development of many changes, the instrument is difficult to detect. In addition, the radar tilt shot like a torch as straight wave, would form around a radar blind spot monitoring, if a tornado near, and undetectable. Microblogging Recommended | microblogging hot today (edit: SN026)
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