Recently, the thundershowers in the south are very strong, for example, around May 10, the local one-hour rainfall in Qinzhou, Guangxi Province exceeded 100 mm, reaching the short-term heavy rain level, on the afternoon of May 13, the southern towns of Haikou received nearly 70 mm of rainfall in one hour, and the local red warning for heavy rain was issued. Yunnan, which has been in drought for a long time, has also ushered in a wide range of rainfall, and there have also been heavy to heavy rains in the east, which is very beneficial to alleviating the drought.
But in addition to this, in general there is less and less rainfall in the south, and more and more in the north, and more and more in the north. Even in Chongqing, Sichuan, where sunshine has always been scarce, the clouds and fog dispersed on May 13, and the sun was shining, and there was even a bit of a spicy feeling. The consequence of the sunshine in mid-May is well known, that is, the temperature rises rapidly, and most of the country quickly warms up.
In normal years, there will be more precipitation in the south in May than in April. Why is there less rainstorm in the south in May than in April? It starts with two unusually high pressures. This first anomalous high is located over the North Pacific Ocean east of Japan. Since May 7, there has been a stubborn warm high pressure in this sea area, and on May 10, the 5880 line was once raised north to 40 degrees north latitude.
Two days after the adjustment weakened, the high pressure made a comeback on May 13, moving westward and northward with stronger momentum, and the 5880 line may break through 40 degrees north latitude. In addition, there is also a warm high pressure ridge near the northwest of the mainland that continues to be active, under their influence, Turpan has a high temperature of 40 degrees in early May, and this wave of high temperature in mid-May is even more severe, on May 12, Turpan exceeded 41 degrees, and there is a continuous high temperature of more than 40 degrees.
Why are these two high pressures occurring? Why are these two high-pressures so powerful? We'll talk about that later. Whatever the reason, these two highs did arise, and they have already had consequences. In addition to the direct consequences, there is also a very important indirect consequence, that is, between the two high pressures, the cold vortex in the eastern part of the continent is frequently active, and the cold air often winds south from the sea and infiltrates into the south in large quantities after sweeping the northwest, northeast, and north China.
Recently, Xinjiang sand and dust @ Zhongqi Ai photography group in southern Xinjiang Xiao Ai
Because of this, there are many strong winds in the north in May, and there is sand and dust from time to time; Because of this, the air in East China, especially Jiangsu, Zhejiang and Shanghai, is very dry in May, and sometimes there is even the illusion of "high autumn air"; It is precisely because of this that the water vapor in Fujian, Taiwan, Guangdong, Jiangxi, Hunan, Hubei, and even Chongqing, Sichuan and other places has been driven into the sea or driven to the southwest, and the heavy rain in most parts of the south has completely turned off.
Next, there are two or three more cold vortices lining up to the south, and the widespread drying of the continent will continue. Before May 18, the rainfall in the south was very small, confined to western Guangdong, Hainan, Guangxi, Guizhou, Yunnan, Tibet and Sichuan and Chongqing, and the heavy rain was still scattered and scattered. However, after May 18, the monsoon water vapor belt extending from the northern Indian Ocean to the South China Sea will take shape, and the South China Sea summer monsoon may enter a critical state of eruption.
Under the influence of the possible outbreak of the summer monsoon, the heavy rains in the south will re-intensify and expand in scope. Compared with the previous rainstorm, this rainstorm will show the characteristics of more random and more difficult to accurately predict the rainstorm in the warm zone, and because the summer monsoon has been in a critical state of outbreak, the water vapor transport is more intense, the warm humidity is more sufficient, and the intensity of the local rainstorm may be greater. And how big this rainstorm will be, there is another variable, that is, those tropical clouds in the northern Indian and Pacific Oceans, which may intensify into cyclonic storm embryos, typhoon embryos, and even cyclonic storms and typhoons in mid-to-late May.