How to know the weather from the wind?

"The east wind sends the wet west wind dry, and the south wind blows the warm north wind." This proverb is popular in the middle and lower reaches of the Yangtze River, indicating that different winds will bring different weather, such as cold, warm, dry and wet.

Understand the weather by observing the wind.

The middle and lower reaches of the Yangtze River face the ocean in the east and the mainland in the west. The wind here blows from east to west and from south to north, shouldering the task of exchanging cold and warm and transporting water vapor. The east wind is wet and the south wind is warm. The warm and humid southeast wind provides abundant water vapor conditions for the formation of clouds and rain. As long as there is an opportunity to rise, it will condense clouds and cause rain. Therefore, there is a saying that "ask the distance of rain, look at the southeast wind" and "southeast wind during the day, wet cloth at night". The west wind is dry, the north wind is cold, and the northwest wind blows on sunny days, indicating that it will continue to be sunny and cold without rain; The northwest wind blows in rainy days, indicating that the dry cold air is already under pressure. With the thickening of the cold air layer, the clouds in the air will rise and become thinner, and soon the clouds will disappear. Therefore, the proverb says, "the northwest wind opens the door."

In temperate regions, if there are two opposite winds on the ground, it is often two large-scale and large-scale cold and warm air currents with different temperatures and humidity. The south wind carries warm and humid air, while the north wind carries dry and cold air. Where they met, a front was formed. The upward movement of warm and humid air is the most intense in the front area. Sometimes the warm and humid airflow is strong, and it actively attacks the north, slides upward on the cold airflow, and cools the condensed clouds. At this time, the direction of clouds (warm air flow) in the sky is opposite to the wind direction (cold air flow) on the ground. "If you go against the wind, there will be rain." With the rapid development and thickening of clouds, a large range of persistent clouds and rain have been formed. Sometimes, dry cold air is more powerful than warm wet air. It took the initiative to attack, like a wedge inserted directly under the air, to lift the warm and humid air upward, and a thunderstorm cloud belt appeared in the front area. In this area, there is lightning and thunder, and the wind and rain suddenly rise.

The movement of cloud and rain belt on the front is determined by the rise and fall of north-south airflow. The south wind blows strongly somewhere, indicating that the place is in the south of the frontal cloud and rain belt. At this time, the warm front is northward, and the weather is sunny and warm. However, "the north wind does not bully the south wind", "the south wind blows to the end, and the north wind returns the gift" and "the south wind blows tightly, and it will rain soon". Every time the south wind blows, although it is sunny for a while and warm for a while, it indicates that the north wind will push the cold front south. Therefore, as soon as the north wind turns, it will rain. The longer the south wind blows, the stronger the force of warm and humid airflow. The cold air in the north goes south, the more likely it is to have a close tug-of-war, which will make the front swing and wander in this area, and it will form a continuous rainy and quiet front weather. Therefore, there is a saying that the southeast wind has been blowing for a long time and will not dry for half a month. If the cold air force is particularly strong, the cold front clouds and rain in the south are often swept away and pushed to the ocean in the south; The greater the north wind, the longer the sunny day. So "the south wind is rainy and the north wind is sunny."

The movement of high pressure and low pressure is often expressed by blowing. If there is no wind on a sunny day under high pressure control, it means that the high pressure system has not moved obviously and the sunny day continues; On rainy days under the influence of low-pressure system, if there is no wind, it means that the low-pressure system rarely moves, so it keeps raining. The precipitation low-pressure system in the middle and lower reaches of the Yangtze River mostly moves from the west. Therefore, the wind direction before the rain mostly moves eastward and counterclockwise all the year round, that is, the wind direction changes from southeast to east to northeast; On the contrary, if the wind direction changes from southeast to west, it will not rain generally, and it is only possible to rain when there are local cumulonimbus clouds in summer. The proverb says, "East wind blows less in four seasons", which means that the low-pressure system affected the local wind direction before. There is also a saying that "the east wind will be born after the rain, and the rain will be more fierce in the future": that is, after the rain stops, there will still be three or four east winds, which is a sign of the suspension of rainfall, indicating that there is still a low pressure moving westward and it will be rainy in the future.

Generally speaking, the rainfall from the northeast wind lasts for a long time and is heavy. If the wind direction is sometimes northeast and sometimes southeast when it is going to rain or starting to rain, it is called "a gust of wind"; It indicates that the moving low-pressure system has a large range and moves slowly, and there will be continuous rainfall in the future.

On rainy days, if the wind turns west, it will probably clear up. The more northwest the wind, the stronger the wind, the faster it clears up, and the longer the sunny day lasts. Sometimes the west wind is small and the weather is still unclear, which belongs to "easterly rain, sunny west wind;" If the west wind is not clear, it will be cloudy. If the south wind or southwest wind clears up, it often doesn't last long, indicating that the next rainy period is near.

Sometimes the east wind blows for two or three days, and the weather remains the same, but the wind is getting tighter and tighter. This happens mostly in dry days; At this time, the temperature is "warm in the day and cold in the night", which is called "the weather is dry and the east wind is tight" and "the east wind is cold and there is a great drought". When the low pressure controls the local area, the easterly wind is not strong, and cyclones often appear near the ground in the afternoon, indicating the recent drought. "East wind blows, west wind blows. If it rains in the second half of the month. " That is to say, in a day or two, the wind direction is sometimes east and sometimes west, which indicates that there will be no strong weather system invasion and no precipitation in the medium term.

It is worth noting that the same wind does not necessarily lead to the same weather. The weather depends on the specific situation:

(1) Look at the season. In summer, warm air flow is stronger than cold air flow. As soon as the southeast wind blows, the cloud and rain belt in front pushes north. At this time, under the control of a single heating flow, the air in the middle and lower reaches of the Yangtze River lacks the conditions for upward movement, so there is a saying that "the east wind rains three seasons a year, and the east wind is sunny in midsummer". If the Pacific subtropical high is controlled stably, the summer monsoon will prevail. Although the summer monsoon comes from the southeast ocean, the air flow under the control of high pressure is stable, and the weather is sunny and hot with little rain, so it is "southeast wind, dry". If the northwest wind blows in summer, it indicates rain, so there is a proverb that "winter is fine and summer rain" and "the north wind gives birth to summer rain".

Cold air is stronger than warm air in winter, and northwest wind often pushes the frontal cloud and rain belt to the southern ocean. At this time, under the control of single cold air, the weather in the middle and lower reaches of the Yangtze River is fine, as the proverb goes, "the fields in the northwest are dry after autumn" and "the fields in the northwest are dry after spring"; It will clear up in winter and northwest China. "If the southeast wind blows at this time, but the duration is not long, this is' the south wind blows to the end, and the north wind returns', which indicates that the cloud and rain belt ahead will affect the local area and the sky will turn cloudy." Ask about the distance of the rain, but look at the southeast wind. "

(2) Look at the wind speed. As the saying goes, "there is rain in the east wind, but it is too elegant". Only when the east wind roars day and night can it "rain wildly"; Only when the southeast wind is tight can it rain fast and hard. In dry days in winter, it will take two or three days for the easterly wind to rain; If the wind reaches five or six, it may rain for a day or two. In the rainy period of early summer, it will rain as long as the southeast wind blows for a while.

In addition, "the wind is the first rain, and the wind is crazy and the rain is closed." Before a shower, it is often the wind that blows first and then the rain falls. When the rain stops, the wind increases first, and then the rain stops, that is, "the strong wind overwhelms the fierce rain." This phenomenon occurs under cumulonimbus clouds. Because the cumulonimbus cloud is approaching the rain area, there is wind first, then rain. When the wind and rain are heavy, the rain area passes quickly.

(3) Pay attention to locality. We must distinguish between "Zhen Feng" and "false wind". In general, wind direction and wind speed have different diurnal variation laws in different places. This normal daily variation law can't reflect the influence of weather system, so people call it "false wind". Only when the wind direction is stable in a certain direction and the wind is gradually increasing, can it be the "Zhen Feng" that can predict the weather change. Generally, "Zhen Feng" should be scraped from morning till night, and scraped from night to midnight; Especially the night wind, it is more conducive to forecasting the sunny weather. As for the local mountain valley wind, it also belongs to the "false wind" and cannot be used to predict the weather turning point.