A tornado occurred in Conghua District, Guangzhou. What was the reason? What is the current situation?

Due to the large number of residential areas near the tornado landing area and the popularity of short videos, a large amount of high-quality video material has been left behind. The rotation speed of this tornado is relatively high and the wind column is relatively stable. It may eventually be rated as EF1-EF2 in intensity.

Because the tornado crossed the track of Line 14, the operation of the Dajiao section of Line 14 was also affected. There are currently no reports of casualties

.

It has caused some damage in urban areas, such as tents blowing over, trees falling and even uprooting, etc. It is really dangerous if you happen to be hit.

The formation of tornadoes often requires high convective effective potential energy, low lifting condensation height, high low-altitude humidity and strong wind shear

conditions.

1. At a higher altitude of 200hpa, Guangdong is on the east side of the South Asian High and is located in the diversion area of ??the high-altitude westerly jet stream. It has strong high-altitude divergence

and is promoted by suction. Convergence movement occurred at low altitude. High-altitude divergence takes away the heat released by latent heat, which is also conducive to the maintenance and strengthening of convective wind storms. To sum up, today's Guangdong does have conditions sufficient to support the occurrence of deep moist convection.

As for sounding analysis. Select Hong Kong Sounding. From soundings in Hong Kong, it can be seen that almost the entire troposphere is a wet layer, with excellent water vapor conditions. There is a certain degree of reverse wind direction at low altitude, which means the intrusion of warm advection (southwest monsoon). Due to the continuous energy provided by the southwest monsoon, the convective effective potential energy has reached above, indicating abundant thermal conditions. The southwest monsoon also brings low-altitude vertical wind shear. The wind shear is not too strong, but it is enough to support the conversion of horizontal vorticity into vertical vorticity, and also allows for the structure of mid-level mesocyclones

A certain degree of downloading. In addition, the sounding shows that there is a significant low-altitude wet zone. The LCL height is only 600m. Low-altitude and high humidity are indeed a major benefit for tornado landing.

2. Taking these conditions together, STP has reached 1.1, which also indicates the potential for tornadoes to occur. It is worth noting that before a convective storm is triggered, its background environmental wind field tends to strengthen, which means that the vertical structure of the convective cell is strengthened as it develops, bringing stronger The rising speed and mesoscale vertical wind shear are further conducive to the organized development of storms

The formation of super cells, and the increased low-level winds are more conducive to tornadoes touching land. Due to the limited intensity of the tornado, it did not leave many traces on the radar. Before and after its landing, the radar radial velocity map only showed a mesocyclone with a speed shear of about 25m/s. The intensity should be medium and could not meet the domestic TVS standard, that is, short-range speed.

Degree shear 45m/s. Of course, this may also be due to the resolution and volume scan frequency interval. As the most economically developed city in China

Guangzhou has a higher resolution phased array radar, which should be able to provide better indications and predictions for the occurrence of such tornadoes

Police.

3. The Pearl River Delta, or the entire Guangdong, is the first stop for the southwest monsoon to hit land, and there are more typhoon activities. In fact, it is one of the major tornadoes in my country

In high-incidence areas, there are some tornadoes that are not very strong. In fact, there is no need to make a fuss. Just treat it with a normal mind and don't involve too much. This afternoon I paid attention to the supercells located in Jiangsu: especially the supercells at the junction from Yancheng to Huai'an, the basic reflectivity is very considerable.

However, although Jiangsu Xiangshui issued a tornado warning today, in fact, there should be no tornadoes touching the ground. Instead, there were tornadoes touching the ground in the convection system in the warm zone of Guangdong.

It is difficult to see the existence of supercells in the radar reflectivity in Guangzhou, but the photos taken by netizens in Foshan still show this CL (typical), which is different from HP high precipitation and LP Low precipitation) supercell spectacular. Of course, this Foshan supercell should not be the system that caused the tornado in Taiping Town, Conghua District, Guangzhou.

Here is a look at the radar map of the place where the tornado occurred:

From the basic radar reflectivity and speed map, we can see that the radar characteristics of tornadoes are not obvious, and there are no hook echoes and high altitudes. Wind shear. However, according to the photos and videos posted at the scene, it can be judged that the power of this tornado is not too small. It is estimated to be at EF1 level. The specific wind damage has not been reported yet, and it may still be possible in the local area. Causing wind damage to EF2.

4. On the 500hpa field, it can be seen that there is a trough from Hunan to Jiangxi. The ground convergence in front of the trough accelerates the water vapor jet stream from the South China Sea to move northward, and appears at 850hpa in the Guangdong and Guangxi areas

Before and after the high-intensity southwest jet stream, there is a high-intensity warm and moist inflow near Guangzhou, which rises and triggers thunderstorm clouds. The supercell near Foshan is also formed in this way. Thunderstorm clouds near Conghua District of Guangzhou may form tornadoes and touch the ground under certain vertical wind shear conditions. In fact, it can be roughly identified from the perspective picture that it may also be a super cell, and the outline of the wall cloud and mesocyclone can be roughly seen.

But the radar reaction is indeed not obvious.

5. In fact, from a prediction perspective, although the physical condition index is still very good, the STP (Significant Tornado Index) does not indicate the possibility of a tornado. Therefore, this local tornado was unexpected.

It is understandable that the prediction and warning of tornadoes is a global problem.

The Guangdong and Guangxi regions will still be within the scope of this jet stream in the next week, and they need to continue to guard against the impact of strong convective weather. A tornado is a form of severe convective weather, which is a small-scale violently rotating funnel-shaped airflow under unstable weather conditions that can extend from the ground to the bottom of a severe thunderstorm.

The central wind force can reach 50-150m/s, and the width of a tornado is usually between 50m-1km, but there are also larger ones. The El Reno tornado in Oklahoma was 4.2km wide at the base.