What is cold front weather?

Cold front can be divided into two types: the slow moving one is called the first cold front or the slow moving one, and the fast moving one is called the second cold front or the fast moving one.

The front of the first kind of cold front is in front of the trough line at high altitude, and it is mostly stable weather. The front moves slowly, and the front slope is not big (about 1%). The cold air behind the front forces the warm air to rise steadily along the front. When the warm air is relatively stable and the water vapor is abundant, a wider layered cloud system similar to the warm front will be formed. Only the cloud system appears behind the front, and its distribution order is opposite to that of the warm front cloud system. The nature of precipitation is similar to that of warm front, and stratocumulus and broken rain clouds often form in the precipitation area near the front. The precipitation area appears behind the front, mostly stable precipitation. If the warm air in front of the front is unstable, cumulonimbus clouds and thunderstorms often appear near the ground front. The cold front weather in northwest China, north China and south China in summer mostly belongs to this type.

The second cold front weather model is a cold front with fast moving speed and large slope (1/80~ 1/40). The cold air behind the front moves much faster than the warm air mass, affecting the warm air mass and forcing it to rise strongly. On the other hand, at the top floor, because the warm air mass moves faster than the cold air, the warm air slides down the front. Because this front is located behind the trough or near the trough line, the rising motion near the front and the sinking motion in the upper front area are further strengthened. In summer, near the ground front of this cold front, there are generally strong convective unstable weather such as cumulonimbus clouds, thunderstorms and even hail and squall lines, but no clouds are often formed on the high-level front. Therefore, the second kind of cold front cloud system presents a long and narrow accumulation cloud belt arranged along the front line, like a cloud dike with a width of about 10 km and a height of 10 km. Stratospheric clouds, cumulus clouds and cumulus clouds often appear in front of the ground front. When this cold front crosses the border, dark clouds often roll, strong winds blow, lightning flashes and thunder rumbles, heavy rains pour down, and meteorological elements change dramatically. This kind of weather lasted for a short time. After crossing the front line, the sky suddenly cleared up. In winter, due to the low humidity of the warm air mass, it is impossible for the temperature to develop into strong unstable weather. Only cirrus, cirrostratus, stratus, nimbostratus and other cloud systems appear in front of the front line. When the water vapor is sufficient, there may be thick and low clouds and small continuous precipitation near the ground front. After the ground front crosses the border, the clouds quickly disappear, the wind speed increases, and strong winds often appear. In dry season, the air humidity is low, the ground is dry and bare, and there will be sandstorm weather. This cold front weather mostly occurs in winter and spring in northern China.

The cold front has a wide range of activities in China, almost all over the country, especially in the winter half year, and it is more common in the northern region. It is one of the most important weather systems that affect the weather in China. In winter, the air in mainland China is dry, and the cold front mostly enters the north of China from Russia and Mongolia, and then goes south. The cold air brought from Siberia meets the local warm air, and almost no precipitation forms on the front. Therefore, when the cold wave and cold front cross the border in winter, only strong winds and cool weather are formed. There are more than two types of cold fronts in winter, which can reach South China, but after moving to the Yangtze River basin and South China, they often turn into one type of cold front or quasi-static front. There is more than one cold front in summer, which has a small influence range and generally only reaches the Yellow River Basin. Thunderstorm weather in summer in northern China is closely related to cold front activity.