There are frequent strong winds and rains along the coast of South China and the South China Sea. Why have typhoons been frequent since October?
Beijing News Express (Reporter Deng Qi) This week, the 19th typhoon "Swan" and the 20th typhoon "Aishani" will affect our country successively this week.
In October, typhoons "Canhong", "Lianhua", "Langka", "Shader" and "Molafi" occurred one after another.
On November 3, experts from the Central Meteorological Observatory stated that typhoons are frequently due to the subtropical high and the South China Sea monsoon, which provides a place for typhoons to generate in the southern sea, and the latter provides water vapor energy.
This year's No. 19 typhoon "Swan" path probability forecast map in the next 60 hours.
Picture from Central Meteorological Observatory
According to Zhang Ling, chief forecaster and senior engineer of the Central Meteorological Observatory, since October this year, typhoons have frequently "onlined" and have occurred under the background of the strong subtropical high, the ridge line to the north, and the west extension of the ridge to the west.
So far, the South China Sea monsoon has not ended, which is significantly later than the multi-year average of the South China Sea monsoon. In addition, since October, the cross-equatorial airflow has often been stronger. The combination of the above favorable conditions provides better conditions for the South China Sea and nearby waters. Typhoon generation and activity background conditions.
She explained that the subtropical high control zone is a downdraft, which is not conducive to the occurrence of convection (the typhoon develops from convection).
In October of this year, the subtropical high pressure ridge line was located to the north and the west ridge point to the west, which made more room for typhoon activities in the South China Sea area, or that the typhoon had relatively enough "movement venues."
This year's No. 20 typhoon "Aishani" path probability forecast map for the next 120 hours.
Picture from Central Meteorological Observatory
Generally speaking, the South China Sea monsoon ends on the 1st to 2nd pentad of October and has not ended so far this year. It has become the main provider of low-level water vapor and energy input for typhoons.
Therefore, the subtropical high and the South China Sea monsoon are in perfect harmony. The former provides a venue for typhoon generation in the southern seas, and the latter provides water vapor energy.
Data show that from 1949 to 2019, there were an average of 3.77 typhoons generated in October during the same period in history, of which 0.56 landed in my country.
In October this year, the number of typhoons generated was at least 1.33 more than the historical period, and the number of typhoons that landed in my country was 0.44 more than the historical period.
The Central Meteorological Observatory said that the recent typhoons have occurred one after another. Due to similar routes, the coast of South China and the South China Sea have experienced frequent strong wind and rain.
At present, the 19th typhoon "Swan" heading towards Vietnam and the slow-growing typhoon No. 20 "Aisani" will both bring wind and rain effects to the South China Sea.
It is estimated that there will be 6 to 7 strong winds in the southern East China Sea, Taiwan Strait, Bashi Strait, Beibu Gulf, most of the South China Sea, Zhongsha Islands, Xisha Islands and the coasts of Zhejiang, Fujian, Guangdong, and the eastern coast of Hainan Island today and tomorrow. The Taiwan Strait, the Zhongsha Islands and the eastern seas of the Paracel Islands will have strong winds of magnitude 8-9, and gusts of up to 10-11.
From the night of the 3rd to the 5th, there will be heavy to heavy rains in the central and eastern parts of Hainan Island; from the 3rd to 5th, there will be heavy to heavy rains in the Zhongsha Islands and Xisha Islands, with heavy rains locally.
The Central Meteorological Observatory continued to issue blue warnings for typhoons this morning.
Beijing News reporter Deng Qi