A strong tornado in Guangdong caused many casualties. How should we prevent it?

Around 15:00 on April 27, a tornado hit Zhongluotan Town, Baiyun District, Guangzhou, killing five people and injuring 33. According to the Guangdong Meteorological Bureau, the tornado was initially judged to be level 3, a strong tornado, and moved about 1 kilometer. The Liangtian Village Weather Station, about 2.8 kilometers away from the tornado site, recorded a maximum gust of 20.6 meters per second (level 8).

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01 Why did a strong tornado and large hail occur in Guangzhou? Professional analysis by the meteorological department: 4 reasons

Around 15:00 on the 27th, a tornado occurred near Liangtian Village, Zhongluotan Town, Baiyun District, Guangzhou. The Guangdong Provincial Meteorological Bureau organized an expert team to conduct on-site disaster investigations and conducted a preliminary survey of the tornado's impact path of about 1.7 kilometers, with a maximum impact width of about 280 meters. The tornado was initially determined to be a strong tornado. A tornado is a rare localized, small-scale, sudden severe convective weather that occurs under extremely unstable weather conditions. The meteorological department initially analyzed that there are four reasons for the strong tornado and large hail in Guangzhou this time:

(1) Over the past period of time, the warm and humid air currents from the southwest of the South China Sea have continued to strengthen, transporting a large amount of water vapor and energy to Guangzhou. Guangzhou has been in an unstable state of high temperature and high humidity for a long time, and a large amount of unstable energy has accumulated near the ground.

(2) On the morning of the 27th, warm and humid air currents in the near-ground layer continued to increase, and abnormally high absolute humidity was recorded at several meteorological observation stations.

(3) The low-level jet stream strengthened during the day on the 27th, exacerbating the unstable stratification of "cold on top and warm on the bottom".

(4) The passage of mesoscale convergence lines on the ground and high-altitude waves serve as triggering conditions, triggering strong updrafts, causing the parent storm of the tornado to develop strongly.
02 What is the difference between a tornado and ordinary extreme winds? How many levels can they be divided into?

The main difference between a tornado and an ordinary extreme wind is that a tornado is a rotating wind, smaller in scale, and is conspicuous by its funnel cloud and swept debris, and has a very low central air pressure, which can easily cause greater damage.

Ordinary extreme gales are straight-line gales, which have relatively no clear visual image, and the extremeness of their disasters is generally lower than that of tornadoes. In addition, ordinary extreme gales are more instantaneous gusts, while strong tornadoes can last for tens of minutes. Tornado speeds are not directly observed, so they are not defined by the commonly used Beaufort wind speed scale. Instead, their strongest wind speed and rating are inferred based on the degree of damage they cause.

Tornadoes in China are mainly divided into four levels .

A level 1 tornado is weak, with the maximum near-ground gust wind speed (hereinafter referred to as Vmax) less than or equal to 38 m/s;

The intensity of a Level 2 tornado is moderate, 38 m/s < Vmax ≤ 49 m/s;

Category 3 tornado intensity is strong, 49 m/s < Vmax ≤ 74 m/s;

A Category 4 tornado is considered super strong, with Vmax>74 meters per second.

03 Which areas in my country are prone to tornadoes? How to deal with and prevent them?

When the weather conditions are met, tornadoes are more likely to occur in plain areas. For China, the middle and lower reaches of the Yangtze River plain , the Pearl River Delta, the Northeast Plain , the North China Plain and other areas are all areas where tornadoes occur more frequently. Plain areas are densely populated areas, so special attention should be paid to prevention and response.

According to the characteristics of tornadoes and the limitations of forecasting and warning, there are three levels of prevention:

(1) In the long term before the weather occurs, such as a few hours to a few days, the weather forecast will provide a more reliable guess about the possibility of the occurrence of tornado background, that is, severe convective weather. From this time on, attention should be paid to subsequent nowcast warnings;

(2) When the meteorological department issues a near-term forecast warning a few minutes to a few hours in advance, you should reduce going out and stay in a safe place to avoid severe convective weather and possible tornadoes;

(3) When facing the threat of a tornado, if you are outdoors, observe the tornado's movements and avoid its path in a timely manner. If you are indoors, stay away from doors, windows and the outer walls of the house, and hide in a relatively sturdy, permanent reinforced concrete structure with your head covered and crouched down. The safest place is a basement or semi-basement. In emergency situations such as falling electric poles or collapsed buildings, the power supply should be cut off in time to prevent electric shock or fire. When traveling by car and encountering a tornado, do not drive away or hide in the car. Leave the car immediately and take shelter in a low-lying area.

Comprehensive sources: Xinhuanet, China Meteorological News, etc.