On the afternoon of September 16, from the cloud map of the Fengyun No. 4 high-definition visible light satellite, the two key points on China's weather stage today are the long autumn rain belt in the western and northern regions, and the typhoon Candu circling in the East China Sea. But in fact, there is also a region where the weather is also quietly changing drastically - in Guangdong, some inconspicuous clouds begin to erupt rapidly in the afternoon, and these clouds, although small in scope, are actually extremely strong!
It is not difficult to see from the afternoon radar map of South China that these small-scale clouds along the south China coast are actually extremely powerful thunderstorm clouds, and the radar map is a small but dark red radar echo, under these deep red echoes, some areas have appeared rapidly changing color in the afternoon or even day and night, and encountered short-term thunderstorms, strong winds, hail and other fierce weather attacks!
For example, some Guangzhou netizens have photographed the amazing "mountains and sea clouds" - the clouds are like huge waves coming from the sky, which is produced by the development of extremely strong thunderstorms, representing fierce convective activities.
According to netizen reports, hail has occurred in Zhuhai, Hong Kong, Taishan, Shenzhen and other places, the Hong Kong Observatory issued hail reminders, and the Taishan Meteorological Observatory hung an orange warning of hail. Some netizens have to ask: Is this weather a precursor to the typhoon? In South China, hail is not uncommon, and during the pre-flood season in spring, hail often comes with strong convective weather such as thunderstorms and strong winds. However, in September, hail is relatively rare in southern China, not that there will be hail if there is strong convection, but that the freezing layer needs to be low enough.
In the first stage of the pre-flood season in South China, especially in the period from April to mid-to-late May, strong convective weather is often accompanied by hail, because the temperature in Guangdong Province during this period is not so high, the atmospheric freeze layer is relatively close to the ground, and there is often a weak cold air effect, hail can often fall to the ground. But in September, the subtropical high pressure in South China is often still strong, and the freezing layer is not low enough to be suitable for the atmospheric conditions for hail occurrence. Hail reported in many parts of South China today shows that cold air masses have invaded the upper layer of the troposphere and are rapidly cooling at high altitudes.
For East Asia, this may be a sign of a change in the upper atmosphere of south Asian high pressure and westerly wind belt, and a feature that circulation patterns may be changing, but this does not necessarily mean that the high temperature in south China is coming to an end, because the range of cold air intrusion from the bottom of the atmosphere during this period is still quite limited, and cooling may only rely on the outbreak of thunderstorms.