Will there be a tornado on the river?

On June 0, 20 15, a passenger ship carrying more than 400 people was suddenly hit by a tornado and capsized in the Shishou section of the Yangtze River in Hubei Province. This passenger ship sails from Nanjing to Chongqing. Up to now, the State Council has characterized the accident as "the East Star sank due to strong wind and heavy rain".

Based on the existing reports, the local wind reached 12 at the time of the accident, and the precipitation within 24 hours was 150.6 mm.

Tornado is a very violent weather phenomenon, which is formed by the vertical hollow tube caused by the rapidly rotating airflow. The United States suffers the most tornadoes in the world, with an average of 100000 thunderstorms and 1200 tornadoes every year, with 50 deaths.

Tornado weather is rare in China, and there is a lack of experience in forecasting and dealing with this kind of weather. Once this kind of accident happens, it is more likely to cause greater losses.

The incident occurred in the river, far away from the tornado-prone sea surface and inland plains. Considering the heavy rain at that time, the culprit of the accident is likely to belong to a category under the tornado: "gust roll". This is a small vertical rotating airflow associated with gust front and downburst. When the fast-moving dry and cold airflow overflowed by thunderstorm flows through the static warm and wet airflow at the overflow edge, it will cause the rotation effect. If the wind shear at the lower level is strong enough, this rotation will affect the ground, and the final result is gust.

According to the Beaufort scale, when the wind reaches 12 and the wind speed exceeds 1 18 km/h, huge waves will be caused when it appears on the water surface: the air on the sea surface is all waves and white, and the whole sea surface is white; Huge waves poured down like rivers, greatly reducing visibility. It rarely appears on land, and if it forms, it will cause extensive and serious damage to buildings.

In some developed countries, at the beginning of the tornado season every year, schools and media in tornado-prone areas will publicize the dangers of tornadoes and educate them how to improve their chances of escape when tornadoes appear. In the United States, where tornadoes occur frequently, citizens are often advised to buy special weather radios, and they can receive dangerous weather warnings issued by the National Weather Service. The alarm was broadcast on both radio and TV. Most societies have civil defense alarms, which will be activated before they think a tornado is coming.