[Source: Xinmin Evening News] Source: @上海市 Weather The maximum wind force near the center was level 10 (25 m/s), and the lowest air pressure in the center was 990 hPa. However, it is still not stopping, and it is very likely that it will make landfall again in Pudong, Shanghai or

[Source: Xinmin Evening News]

Source: @上海市 Weather

Xinmin Evening News (Reporter Ma Dan) The impatient "Plasang" ran all the way and was already in Daishan, Zhoushan City, Zhejiang Province around 6:50 this evening. It made landfall along the coast of the county. At the time of landfall, the maximum wind force near the center was level 10 (25 meters/second), and the lowest air pressure in the center was 990 hPa. However, it is still not stopping, and it is very likely that it will make landfall again in Pudong, Shanghai or Jinshan and Fengxian areas. Affected by this, there will be heavy winds and rain in Shanghai tonight, and heavy rain will occur in some areas.

Be wary of dangerous semicircle risks

As the subtropical high pressure has weakened significantly, it is still not ruled out that "Plasang" may make landfall again in Jinshan and Fengxian areas, and the impact of wind and rain will also be more obvious. Although "Plasang" is not as strong as "Bebiga", even if "Plasang" does not land in Shanghai, because Shanghai is in the "dangerous semicircle" on the right side of "Plasang"'s path, there will be heavy wind and rain tonight. obvious.

From this evening to midnight, there will be showers and short-term thunderstorms in this city. There will be heavy rain (60-90 mm) in the east of Pudong, Fengxian, Jinshan, Qingpu, and Chongming, and heavy rain (30-45 mm) in other areas. The wind force is also gradually increasing, and the strong wind is expected to continue until the early morning of the 20th. The maximum gust in the central city is level 7 to 8, level 8 at an altitude of 30 to 60 meters, level 9 above 100 meters, and the top level of Lujiazui's "three-piece suit" can reach level 9 to 8. Level 10, the maximum gust level is level 9 to level 10 in the eastern parts of Pudong, Fengxian, Jinshan and Chongming, and the gust level is level 10 in Yangshan Port area.

The dangerous semicircle was actually originally a term in navigation science and technology. When a typhoon moves from east to west (or northwest), because the right side of the typhoon's forward direction is adjacent to the western Pacific subtropical high, the density of the air pressure distribution around the typhoon is uneven, and the distribution of its strong wind areas is also uneven. Generally speaking, the side adjacent to high pressure has high wind speed, wide range, and high waves, which can easily cause shipwreck accidents; on the contrary, the side close to low pressure has low wind speed, narrow wind area, and low waves. Therefore, the right semicircle of a typhoon is called the "dangerous semicircle" and the left semicircle is called the "navigable semicircle".

Landing does not mean the end

"During the impact of this typhoon, on the one hand, we must be alert to the risks caused by Shanghai being in a dangerous semicircle when the typhoon passes through. On the other hand, after 'Plasang' moves away, Its residual cloud system will also combine with the cold air to bring continuous heavy rain or even heavy rain to the Yangtze River Delta region. Wu Rui, chief service officer of the Shanghai Meteorological Bureau, reminded that the landing of the typhoon does not mean the end of the impact, and sometimes wind and rain will continue. continued.

From birth, development and landing at sea, typhoons advance all the way, often accompanied by powerful destructive power. There are usually two endings after a typhoon makes landfall -

One is weakening and dying. The gradual demise of typhoons is mainly due to two factors. On the one hand, compared with the sea surface, the land is rougher and has many obstacles. Friction will consume the energy of the typhoon and make it weaker. On the other hand, there is sufficient water vapor on the sea surface, which can continuously replenish energy for typhoons. However, after landing, that is, after running on land, the energy source decreases rapidly, and the typhoon will continue to weaken and die.

The second is that after the typhoon transforms into an extratropical cyclone and moves northward to the temperate zone, its warm core symmetrical structure is destroyed. The influx of cold air and the formation of a deep cold center make it lose the characteristics of a tropical convective system. Eventually it transforms into an extratropical cyclone. However, the degeneration of a typhoon does not mean that its wind and rain influence is weakened. On the contrary, during the degeneration process, its combination with cold air may cause the extratropical cyclone to excite stronger energy and bring stronger storms and rains.

Wu Rui said that the landing of the typhoon does not mean the end. After the typhoon makes landfall, its intensity will gradually weaken, but it still carries abundant warm and moist air. The interaction of this warm and moist air with cold air may cause heavy rains or even heavy rains, as well as strong weather such as thunderstorms and local tornadoes. Even if the typhoon ceases to be numbered, it does not mean that it is completely dead. Its remnants will still have serious impacts.

Therefore, people should not only pay attention to whether "Plasang" will land in Shanghai for the second time. From the 21st to the 22nd, the residual cloud system after "Plasang" will make landfall will also combine with the cold air moving southward in the latter part of the 21st. , bringing heavy rain to the Yangtze River Delta region, and heavy rain will occur in some areas. Shanghai will also experience heavy rain to heavy rain from the 21st to the 22nd, with concentrated precipitation from the night of the 21st to the morning of the 22nd.