How big will this rainstorm be in Beijing?

How big will this rainstorm be in Beijing?

China Weather Network reported exclusively that the circle of friends has been sharing the heavy rainfall in the Imperial City for the past two days. Some people say it is the strongest rainstorm in six years, some people say it has exceeded 201July 2 1 2, and friends outside the circle of data emperor are going to take tomorrow off ... So, how serious is this rain?

This rainstorm is imperative.

Simply put, the key to precipitation is like twisting a towel, one must have strength and the other must have water vapor. The material source of precipitation comes from the water vapor transported from the sea by the southerly airflow, and then it is lifted to the high altitude and condensed into water droplets, frozen into ice crystals, and then falls due to gravity. Therefore, the most important conditions for precipitation are water vapor and power.

This time, on June 22-23, North China met the above two basic conditions. Heavy rain is coming. However, when it rains heavily, it still needs water vapor to be continuously transported, and the power can't stop. So how strong is it this time?

This time it won't be as fierce as the rainstorm on July 2, 20 12.

Whenever it rains heavily in Beijing, people always ask whether it will be as heavy as July 2/20 12. After all, this rain can leave a heavy shadow in people's hearts.

On July 2, 2065438, a 20-hour 190.3mm rainstorm occurred in Beijing, equivalent to 2.6 billion cubic meters of water. It was a heavy rain that came and went in a hurry, and the rain was fierce. Beijing 1 hour rainfall generally reaches 40 ~ 80mm, lasting for 3 ~ 4 hours. The heaviest rainfall occurred in Guajiayu, Pinggu, with 1 hour reaching100.3mm, which is extremely rare in the history of Beijing.

Will this rain be as severe as the rainstorm on July 2, 20 12? First, let's look at the water vapor condition. Here is a technical term-dew point temperature. Simply put, the temperature at which water vapor in the air becomes dew is called dew point temperature. The greater the dew point temperature, the greater the water content in the air, and the easier it is to form heavy rainfall.

According to the dew point temperature forecast in Beijing, the dew point temperature on the 22nd with the strongest rainfall is between 18-2 1℃. Compared with July 2, 20 12 1 rainstorm, the overall dew point temperature is lower. Judging from the water vapor conditions, this precipitation process may be inherently weaker than 20 12. In other words, this rainfall may not be as strong as 7.2 1 rainstorm.

This time, it was a long-lasting rain, which was comparable to the heavy rain on July 20th, 20 16.

Remember the "7.20" heavy rainfall last year? In my mind, it is nothing compared with 7.2 1 2 of 201. The feeling is that it has been raining, and there is no big news.

However, due to the high-altitude cold vortex cut off, the rainfall last year lasted longer and more evenly. Compared with "7.2 1", the rainfall process in Beijing lasted 55 hours, 35 hours longer than "7.21"(20 hours). However, the rainfall intensity is relatively uniform, and the hourly rainfall is generally 10 ~ 30mm, which is far weaker than the hourly rainfall of 40 ~ 80mm when it is "7.2 1".

Although the rain is not great, it is not difficult to find from the comparison in the following table that the average rainfall in Beijing, the average rainfall in urban areas and the maximum accumulated rainfall are better than last year's "July 20". Therefore, this "lasting" rain is more than the last "vigorous" rain.

From the dynamic point of view, this process in Beijing this year was driven by high-altitude cold vortex and low-altitude vortex. Because the cold vortex in the upper air moves relatively slowly, the precipitation may start in the form of rough and strong convection, and the precipitation with longer duration will take its place.

These points need to be obtained in the face of the coming rainstorm.

(1) This rain is very heavy, which is the strongest precipitation in Beijing this year.

(2) Convective precipitation is huge and unevenly distributed at the beginning, so beware of strong convective weather;

(3) There may be two precipitation peaks on the evening of 22nd and 23rd, usually heavy rain, and the accumulated amount of the process is large, which may cause road water accumulation, which is unfavorable to traffic, especially in the morning and evening peaks;

(4) Miyun in the northeast of Beijing and Chengde in Hebei may challenge the extreme value of single-day rainfall in June;

(5) There may be more rainfall and higher risk factors in the western mountainous areas and northeast Beijing, so it is necessary to stay away from mountainous areas and low-lying areas as far as possible.