What are the patterns of coastal typhoons? Why do typhoons form at sea?

Movement path?

There is a certain pattern in the path of the typhoon.

The direction and speed at which the typhoon moves depends on the dynamics acting on the typhoon. There are two types of power: internal force and external force. The internal force is the resultant force to the north and west caused by the difference in geostrophic deflection force caused by the difference between north and south latitude in the typhoon range, and the larger the typhoon range, the stronger the wind speed, and the greater the internal force.

The external force is the force exerted by the external environmental flow field of the typhoon on the typhoon vortex, that is, the guiding force of the easterly wind belt of the basic airflow on the south side of the subtropical high in the northern hemisphere. The internal forces mainly act when the typhoon is first formed, and the external forces are the dominant forces that manipulate the movement of the typhoon, so the typhoon basically moves from east to west. Due to the influence of the shape, position, intensity and other factors of the subtropical high, the path of typhoons is not uniform and becomes diverse.

Taking the western North Pacific region as an example, there are roughly three typhoon paths:

1. The westward type of typhoon moves westward from the east of the Philippines, passes through the South China Sea and finally makes landfall on Hainan Island, Guangxi or northern Vietnam in China, and this route mostly occurs from October to November.

2. Landfall type: The typhoon moved northwestward, first making landfall on Taiwan Island, then passing through the Taiwan Strait, making landfall again along the coasts of Guangdong, Fujian and Zhejiang in China, and gradually weakening into a tropical depression. This type of typhoon has the greatest impact on China.

3. Parabolic type: the typhoon first moves to the northwest, and when it approaches the eastern coastal areas of China, it turns to the northeast without landfall, and turns to the vicinity of Japan, with a parabolic path that mostly occurs in May-June and September-November. Eventually, most of them degenerate into extratropical cyclones.

In addition, after the formation of a typhoon, it generally moves out of its source and goes through an evolutionary process of development, maturity, weakening and extinction. A mature typhoon, the cyclone radius is generally 500km 1000km, the height can reach 15km 20km, the typhoon is composed of three parts: the outer area, the maximum wind speed area and the typhoon eye. The wind speed in the outer area increased from the outside to the inside, with spiral cloud bands and showers of precipitation. The most intense precipitation occurred in the area of maximum wind speed, with an average width of 8 km and 19 km, and there was a circular cloud wall between it and the eye of the typhoon. The eye of the typhoon is located in the center of the typhoon and is circular or oval in shape, with a diameter of about 10 km to 70 km, with an average of about 45 km.

The wind speed and pressure in the eye area of the typhoon were the lowest, and the weather was windless, cloudy and dry and warm. As the typhoon intensifies, the eye of the typhoon will gradually shrink and become rounder. Weak typhoons, as well as early-stage typhoons, often do not have a typhoon eye on satellite images (but sometimes a low-altitude typhoon eye appears).

There are many summer and autumn seasons. Especially during the summer vacation, it is more frequent.

This is because coastal cities are closer to the sea, the wind is relatively strong, and typhoons or tsunamis are prone to occur at sea, so these coastal cities are relatively prone to typhoons.

This is because there are no particularly tall buildings to protect this place, and the wind in this place is relatively strong, and it is easily affected by cold snaps, and it is relatively close to the ocean.

Because the coastal city is mainly close to the sea, and typhoons are mainly blown from the ocean.

Because a typhoon is a gaseous vortex formed by the intersection of warm ocean currents and cold winds, they can only appear at sea, and without such warm currents on land, typhoons will naturally not occur.

Two major factors are required for the formation of a typhoon:

1. It requires a large amount of water vapor to be continuously replenished.

2. A relatively broad terrain is required, and only if the terrain is not complicated, a strong cyclone can be formed.

When the sea heats up in summer, the water vapor will evaporate, which will cause the pressure at the sea level to change, and the pressure will change to form cyclones, and strong cyclones eventually form typhoons, which is why typhoons are mostly formed in summer or autumn.

In summer and autumn, when the tropical or subtropical sea water is heated, a large amount of water vapor will evaporate, and the air pressure near the sea surface will be reduced, so that more water vapor will be replenished continuously, and the rising water vapor will rotate under the action of the deflection force of the floor tiles. The water vapor will be liquefied into water droplets, which will exacerbate the evaporation of water vapor, so that the water vapor will continue to be replenished, the air pressure near the sea surface will continue to decrease, and the cyclone will continue to increase, and finally strengthen to form a typhoon.

On the ground, the air cannot be easily vaporized and exothermized, because there is not enough water vapor to evaporate, that is, there is not so much water vapor to replenish, and it cannot be continuously strengthened, so it can only form a cyclone, but cannot become a typhoon. Another reason is that the terrain on the ground is changeable, and there are many blocking terrains, which is not conducive to the formation and strengthening of cyclones.

Typhoons are actually strong tropical cyclones. A tropical cyclone is a severe weather system that occurs in the tropical oceans and moves forward with the surrounding atmosphere like a vortex in a flowing river. Tropical cyclones require enormous energy to form and develop, so they form in tropical oceans with high temperatures, high humidity and other suitable meteorological conditions.

According to statistics, tropical cyclones are formed in tropical oceans around the world except for the South Atlantic.

1. There is a typhoon along the coast.

2. Definition of typhoon: A typhoon is a powerful and deep tropical cyclone that forms over the tropical ocean.

3. Global typhoons mainly occur in 8 sea areas. The northern hemisphere has five sea areas: the western and eastern North Pacific, the western North Atlantic, the Bay of Bengal and the Arabian Sea, while the southern hemisphere has three sea areas: the western South Pacific, the western and eastern southern Indian Ocean.

When a typhoon passes through, it is common for stormy weather to occur, bringing disaster.

The center of this year's No. 5 typhoon "Doksuri" (tropical storm level) is located at 5 o'clock in the afternoon (Beijing time) today (22nd) in the northwest Pacific Ocean about 1030 kilometers east of Manila, Philippines, that is, north latitude and east longitude, the maximum wind near the center has a maximum wind force of 8 (20 meters and seconds), the minimum pressure of the center is 995 hPa, and the radius of the seven-level wind circle is 260-320 kilometers.

It is expected that "Dusuri" will move west-northward at a speed of about 10 kilometers per hour, turn to the northwest on the 24th, increase the speed to about 15 kilometers per hour, gradually strengthen in intensity, approach the sea surface of eastern Taiwan, and begin to affect the southeast coast of China on the 26th.

Typhoon clouds

1) Outer spiral cloud band: composed of stratocumulus or Cucumulus congestus, swirling towards the interior of the typhoon at a small angle.

2) Inner spiral cloud band: Generally, the cloud band composed of several cumulonimbus clouds or Cucumulus congestus clouds is directly involved in the interior of the typhoon.

3) Cloud Wall: It is a concentric circle of clouds composed of towering cumulonimbus clouds around the center of the typhoon, and the cloud top height can reach more than 12 kilometers. It's like a towering wall of clouds.

4) Typhoon eye area: The sky is cloudless due to the sinking of the air flow. If the low-level water vapor is abundant, some stratocumulus clouds and cumulus clouds may also be produced below the inversion layer, but the vertical development is not prosperous, there are more cloud gaps, the water vapor in the typhoon area is abundant, and the airflow rises strongly, which can often cause a large amount of precipitation (200-300 mm, or even more), the precipitation is gustic, the intensity is very large, mainly occurs in the vertical cloud wall area and the inner spiral cloud band area, and there is generally no precipitation in the eye area.