Why do typhoons move northwest?

Typhoons are violent storms that occur in the tropical oceans of the Northwest Pacific Ocean and the South China Sea. You must have seen eddies in rivers from time to time, but in fact, typhoons are air vortices that rotate rapidly around their center in the atmosphere and move forward at the same time. It rotates counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

Meteorologists refer to atmospheric vortices as cyclones, and typhoons are called tropical cyclones because they occur in the tropical ocean.

Why is it called a typhoon? Some people say that in the past, people did not understand that typhoons originated in the Pacific Ocean, and thought that this huge storm came from Taiwan, so it was called a typhoon; It is also believed that typhoons hit Guangdong Province the most in China, and typhoons evolved from the Cantonese word "gale".

In fact, almost all countries and regions in the world located on the west coast of the ocean are not affected by tropical ocean cyclones, but people give them different names in different regions.

Typhoons in the Northwest Pacific and the South China Sea, hurricanes in the Atlantic, Caribbean, Gulf of Mexico and Eastern Pacific, tropical storms in the Indian Ocean and the Bay of Bengal, and tropical cyclones in Australia.

When there is a typhoon in the summer, if you listen to the weather forecast continuously and write down the location of the typhoon center on a map each time, you can see that the path of the typhoon center is basically parabolic and straight, although it changes slightly, and it moves around the earth very regularly. There are two types of forces that move a typhoon: one is an internal force and the other is an external force.

The internal forces are the forces generated by the typhoon itself. Because the typhoon itself is a mass of air rotating in an anticlockwise direction, the direction of movement of the air particles is affected by the rotation of the earth and is deflected. This bias tends to be greater for the typhoon to the higher latitude side than to the equatorial side; In the case of the typhoon as a whole, a force towards higher latitudes is generated, which is the internal force.

It was this force that prompted the typhoon to move northward.

The external force is the thrust of the air around the typhoon when it moves. In summer and autumn, there is often a separate high pressure (commonly known as the subtropical high) in the Pacific Ocean, and the wind direction around this high pressure is very important for the path of the typhoon. The typhoon occurred on the southern edge of the Pacific high, where strong easterly winds blew and the typhoon moved westward.

If memory serves, there is this knowledge in secondary school textbooks.

Briefly: Atmospheric motion.

a The typhoons affecting our country are:Northern HemisphereThe horizontal airflow is counterclockwise and on the eastern side of the cyclone is eastSoutherly wind, southwest wind on the south side and west sideNorthwest wind, northeast winds on the north side. When Typhoon "Fit" was affected, the wind direction was measured in a certain place along the coast of Fujian Province from northwest to southeast, so it was correct to judge that the typhoon's moving path was from southeast to northwest.

b The typhoon affecting China is a cyclone in the northern hemisphere, and the horizontal airflow is moving counterclockwise, when Typhoon "Fit" is affected, the wind direction measured in a certain place along the coast of Fujian Province changes from northwest wind to southeast wind, so it is judged that the typhoon's moving path is from southeast to northwest, so it does not conform to the topic.

c On the east side of the cyclone is a southeast wind, a southwest wind on the south side, a northwest wind on the west side, and a northeast wind on the north side When Typhoon "Fit" is affected, the wind direction is measured in a certain place along the coast of Fujian Province from northwest wind to southeast wind, so it is judged that the typhoon's moving path is from southeast to northwest, so it does not meet the topic.

d On the east side of the cyclone is southeast wind, south side is southwest wind, west side is northwest wind, north side is northeast wind When Typhoon "Fit" is affected, the wind direction measured in a certain place along the coast of Fujian Province changes from northwest wind to southeast wind, so it is judged that the typhoon's moving path is from southeast to northwest, so it does not conform to the topic.

Therefore, a.

1. "Hollow" typhoons: many crossed Taiwan's ** mountain range.

Enter the Taiwan Strait.

The typhoon is more prone to a hollow structure, and when it makes landfall in Fujian, it is easy to have a phenomenon that the north wind is less than the south wind.

2. "Not bad air pressure": When the land was originally a low pressure area, it joined hands with the front of the typhoon, and the pressure difference was small and the northeast wind was small, but after landing, the high pressure zone at sea kept up, the pressure difference increased, and the south wind also increased.

3. "Southwest King Fried."

The typhoon itself is strong, the circulation structure is strong, and the vitality is vigorous, especially the boundary layer is supported by a strong southwest airflow, which can replenish energy downward, so that the southerly wind will be storming all the way to the wind and rain.

Therefore, there is a proverb along the coast of eastern Fujian that "a typhoon is not called big, but it is called big when it returns to the south", and there is also a proverb along the coast of Guangdong that "a typhoon is not big and returns to Nanda".

The phenomenon of returning to the south is inextricably linked to the typhoon's intensity, structure, speed, and surrounding environment. Although not every typhoon has a return to the south, please make sure to let the typhoon turn around for a while before going out with confidence.

Because the earth rotates from west to east, typhoons generally move westward relative to people on earth.

Because typhoons rotate counterclockwise in the Northern Hemisphere, coupled with the special location of the subtropical high. Therefore, typhoons that form in the Northwest Pacific generally move westward.

The Southern Hemisphere is the opposite.

Because of our Chinese.

The geographical situation is in.

The West of the Pacific.

Most typhoons form over the ocean

So typhoons are generally.

East to West.

Mobile!

Because the subtropical high affects the typhoon's movement, it relies on the ambient flow field it provides – strong enough to be in a guiding position. In terms of force, the subtropical high provides the horizontal pressure gradient force of a large pressure field.

When a typhoon is on a vast sea, the main bench is affected by three forces: two external forces, namely the geostrophic deflection force and the horizontal pressure gradient force of the large pressure field, and one internal force, that is, the typhoon internal force. The external force is much greater than the internal force.

The movement of a typhoon is mainly guided by the guiding airflow in the environment, such as the airflow at the edge of the subtropical high and the airflow in front of the westerly trough.

The internal force of a typhoon is the force generated by the north-south difference of the geostrophic deflection force in the typhoon. Since the geostrophic deflection force in the north of the typhoon is greater than that in the south, this north-south difference will cause the internal force of the typhoon to move in a northwesterly direction.

On the way to the "growth" of the typhoon, there is a "big brother" that has a profound impact on it - the Northwest Pacific Subtropical High (hereinafter referred to as the Subtropical High), which is located in the subtropical high pressure belt and is a warm high pressure system that has broken out. During the Northern Hemisphere summer, it is entrenched over the Pacific Northwest and its powerful "body" controls the flow field around it—on its periphery, the upper-air wind field is usually clockwise.

Most typhoons in the Northwest Pacific originate at the southern edge of the subtropical high and usually move along the periphery of the subtropical high. In the early stages of Typhoon Bawei, which affected the northeast of the typhoon this year, the subtropical high stably "circled" the eastern side of the typhoon, and Bawei moved northeast under the influence of its southwesterly airflow (Figure 3). When the intensity of the typhoon is not as good as that of the subtropical high, the typhoon is naturally "led by the nose" by the subtropical high.

The typhoon's path is not just northwestward.

The path of a typhoon can be broadly divided into three categories:

Westward: The typhoon moved westward from the east of the Philippines and passed through the South China Sea before making landfall on Hainan Island in China or northern Vietnam.

Landfall: The typhoon moved northwestward, passed through the Taiwan Strait, made landfall along the coasts of Guangdong, Fujian and Zhejiang in China, and gradually weakened into a depression. This type of typhoon has the greatest impact on China.

In recent years, the two typhoons "9015" and "9711", which have had the greatest impact on Jiangsu, belong to this type.

Parabolic type: The typhoon first moves northwestward, and when it approaches the eastern coastal areas of China, it turns to the northeast without making landfall and turns towards the vicinity of Japan, with a parabolic path.

The typhoons that affect our country are all formed in the tropical ocean. The tropical ocean is a low-latitude region in the western Pacific Ocean, located in the southeast of China. That is to say, the typhoons that affect China all come from the southeast, and then blow on the land of China, and generally make landfall along the coast of Guangdong and Fujian.

Therefore, the typhoons that affect our country are moving to the northwest.

Affected by the deflection force of the Earth's rotation.

The landlord is talking about a typhoon that affects China, right?

The most fundamental reason for this is the result of the combined action of the horizontal pressure gradient force and the geostrophic deflection force.

In autumn, the Eurasian continent is still a center of low pressure, and the ocean is a center of high pressure (to be exact, it should be that the Eurasian continent is in the process of turning from address and pressure to high pressure, but the pressure on the continent is still lower than that of the ocean), so the typhoon formed on the sea surface is blowing to the land.

After the formation of a typhoon, it is deflected to the right by the geostrophic deflection force (the southern hemisphere is biased to the left, and the northern hemisphere is biased), so the typhoon moves northwest after its formation.

Sometimes, when the typhoon is stronger, the typhoon has not disappeared after a long distance, and at this time, under the action of the geostrophic deflection force, the wind direction of the typhoon will continue to deflect, from southeast wind (moving from southeast to northwest) to south wind (moving from south to north), or even southwest wind (moving from southwest to northeast).