Extreme weather will occur in most parts of Spain this week. What is the reason?

The reason of extreme weather in Spain is the special weather caused by low-pressure cyclone, which also happens in China.

There will be very strong gusts in most parts of the southern and eastern Iberian Peninsula, and the wind speed may reach 80-90 kilometers per hour; The Galicia region in the west and the central region including the capital Madrid region will usher in heavy rainfall; It will snow heavily in the northern mountainous area. Due to the strong winds in coastal areas such as Galicia, Valencia, Andalusia and Balearic, the wave is expected to reach 4 meters.

Low pressure, also known as low pressure and cyclone, refers to the atmospheric vortex whose air pressure is lower than the surrounding air pressure on the same horizontal plane. In the northern hemisphere, the wind in the low-pressure area rotates counterclockwise and blows obliquely to the low-pressure center through the isobar. Therefore, at the lower level, the surrounding air converges to the center, forming an upward movement of air near the low pressure center. Because there is updraft in the low-pressure area, water vapor rises and cools down, and clouds cause rain, so the weather is usually bad. If there is a front in the low pressure, the weather will be worse. The low pressure at that time should be called frontal cyclone or extratropical cyclone.

Jianghuai cyclone is the most obvious frontal cyclone formed and developed in the Huaihe River basin and the middle and lower reaches of the Yangtze River. Most of its routes move eastward along the Yangtze River and Huaihe River, and then move northeast through the Japanese archipelago or the Korean Peninsula. The Jianghuai cyclone has a great influence on East China and East China, with rainy weather and even heavy rain. There is a northerly wind in the west and a strong southeast wind in the east of the cyclone, which has caused serious harm to the maritime transportation, operation and fishery in the East China Sea and the Yellow Sea.

The frontal cyclone of the Yellow River is formed in Hetao and the lower reaches of the Yellow River, and its occurrence probability is the highest in summer. Its route is roughly along the Yellow River eastward to the Bohai Sea or the northern part of the Yellow Sea, and then through the Korean Peninsula into the Sea of Japan. In North China, Northeast China, Shandong and other places, it can often cause heavy rainfall or rainstorm, and it will also produce strong winds after entering the sea. Take Shandong Peninsula, Bohai Sea, northern Yellow Sea and Liaodong Peninsula as examples. On a certain day in August, 1998, affected by a strong Yellow River cyclone, there will generally be strong winds and heavy rainfall of magnitude 6~7, which is as serious as tropical storms passing through this area.

This cyclone mainly comes from Mongolia, and it is most common in spring and autumn. There are two migration paths: one is to move eastward into Inner Mongolia, and then continue to move eastward along the lower reaches of Songhua River and cross the Northeast Plain; The second is to enter North China eastward, cross the Bohai Sea eastward and then cross the Korean Peninsula. In northern China, Mongolian cyclone has a great influence on the weather, which is mainly manifested in strong winds, sand blowing and rainfall, among which strong winds are the most prominent. The windy weather in the northern hemisphere in spring is mostly related to cyclone activity.