What was the strongest typhoon in the Northwest Pacific in 2017?

In 2017, the strongest typhoon in the Northwest Pacific Ocean was Typhoon No. 13 "Hato", which was generated on the Northwest Pacific Ocean at 14 o'clock on August 20, and the intensity continued to strengthen, reaching the strongest level of 16, and at 12:50 on August 23, it made landfall on the coast of Zhuhai, Guangdong Province (maximum wind force of 14), bringing major damage to Zhuhai, Hong Kong, Macao and other regions, causing 24 deaths and economic losses of 100 million US dollars; In February 2018, the 50th annual meeting of the Typhoon Committee removed Hato.

Because the Pacific Ocean is the largest and deepest ocean on Earth. The north-western ocean current and the huge energy of the ocean monsoon form more tropical cyclones than any other sea area in the world, with an average of about 35 per year. About 80% of these tropical cyclones will develop into typhoons.

On average, about 26 tropical cyclones reach at least tropical storm intensity each year, accounting for about 31 per cent of the global tropical storm population and more than twice as many as any other region. The Northwest Pacific Ocean is the only area where typhoons occur every month of the year. From 5 to December the average number of typhoons per month is more than one.

The peak period of typhoons is July and October, accounting for about 70% of the total number of typhoons in the year, and August and September are the most, accounting for about 40% of the total number of typhoons in the year. 91% of tropical cyclones in the Northwest Pacific originate between 5°N and 22°N, i.e., from the South China Sea to Taiwan The ocean east of the Philippines, including the Marianas, Caroline and the Marshall Islands.

This is because the Northwest Pacific Ocean has the largest and most extensive ocean surface in the world, a tropical cyclone.

There is a longer period of time to stay on it and the grand feast; At the same time, the tropical Northwest Pacific Ocean is also the warmest place in the global ocean, there are"Warm pool"（warm

pool). The strong East Asian summer monsoon circulation in summer causes a strong upward movement here, which is not only easy to form tropical disturbances, but also conducive to the transport of high temperature and high humidity silver vapor from the ocean to the great high atmosphere, providing favorable conditions for the formation of tropical cyclones.

Typhoons originate in tropical seas, where temperatures are high and large amounts of seawater are evaporated into the air, creating a depression center. With the change of air pressure and the movement of the earth itself, the incoming air also rotates, forming a whirlpool of grinding car air that rotates counterclockwise, which is called a tropical cyclone. As long as the temperature does not drop, this tropical cyclone will become more and more powerful, and eventually a typhoon will form.

The general path of Typhoon Blind is northwest-northeast.

There are more than 20 a year, and there are a few cases of more than 30.

The movement of typhoons is a complex weather phenomenon, which is simply related to atmospheric circulation, large-scale weather systems, and the deflection of the Earth's rotation.

Movement of the typhoon:

The path of the typhoon's center is somewhat variable, but it is basically parabolic and straight. 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 a typhoon itself is a mass of air rotating in an anticlockwise direction (Northern Hemisphere), the direction of movement of the air particles is deflected by the Earth's rotation as it rotates. 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.

The combination of internal and external forces causes the typhoon to move in a northwesterly direction.

Take the Northwest Pacific typhoon as an example: in the winter and spring (November to May of the following year), the typhoon mainly turns northward over the sea east of 130 degrees E, enters the central and southern parts of the South China Sea or makes landfall in southern Vietnam in the south of 16 degrees N, and a few turn northward in the offshore waters of 120-125 degrees E, and a few typhoons may also make landfall in Guangdong in May and November. In the midsummer season from July to September, the typhoon's path shifts further north and west, and China's coastal provinces from Guangxi to Liaoning are likely to be hit by typhoons during this season. In the transitional season of June and October, typhoons mainly turn northward over the sea east of 125 degrees east of the east longitude, and the westward path is relatively northerly, between 15 and 20 degrees north latitude, and a few can make landfall in Guangdong, Taiwan, Fujian and Zhejiang.

Typhoon formation: There are several prerequisites for the formation of a typhoon:

1. Typhoons can only form on the warm ocean surface where the sea surface temperature is higher than 26 -27, and the sea water temperature at a depth of 60 meters is higher than 26 -27;

2. There should be an initial disturbance of the convergence of the lower atmosphere to the center and the outward diffusion of the upper atmosphere. Moreover, the high-level divergence must exceed the low-level convergence in order to maintain sufficient updraft, and the low-level disturbance can continue to intensify.

3. The vertical wind speed should not be too different, and the relative movement of the upper and lower layers of air is very small, so that the latent heat energy released by the condensation of water vapor in the initial disturbance can be stored in the air column in the eye area of the typhoon, so as to form and strengthen the warm center structure of the typhoon;

4. There should be a sufficiently large geostrophic deflection force, and the earth's rotation is conducive to the formation of cyclonic vortices. The geostrophic deflection force is close to zero near the equator and increases towards the north and south poles, and typhoons occur over the ocean about 5 degrees above the equator.

A typhoon is a strong cyclone, so its motion is similar to that of a cyclone, influenced by both external and internal forces

1。From the perspective of internal forces--- it is mainly the result of the action of geostrophic deflection forces.

For the sake of discussion, we can decompose the counterclockwise rotation of the Northern Hemisphere into two forms of motion: one that runs from the outside to the inside, and one that moves in the tangential direction. Under these conditions, look at the magnitude of the geostrophic deflection force.

For the former, the geostrophic deflection force on the east and west sides of the cyclone is equal in magnitude and opposite in direction, so it has no effect on the movement of the typhoon as a whole. In the south, due to the low latitude, the geostrophic deflection force is small and the direction is eastward, while on the north side, the latitude is high, and the geostrophic deflection force is large, and the direction is westward, and the combined force of the two forces must point to the west, which leads to the typhoon to move westward.

For the latter, the geostrophic deflection forces on the east and west sides cancel each other out, while the lower latitudes near the equator experience less geostrophic deflection forces and the direction is southerly, while the north at higher latitudes experiences greater geostrophic deflection forces and the direction is north.

Combined with the above two situations, the typhoon moved to the northwest under the action of internal forces.

2.External guidance, especially the surrounding atmosphere, such as a typhoon in the Northern Hemisphere that appears on the west side of the high pressure (anticyclone), will inevitably move back to the northwest, and if it appears on the east side of the high pressure, it will inevitably move southwest.

In short, the direction of typhoon movement is related to the magnitude of nearby air pressure, isobaric trend, and geostrophic deflection force.

At this time, there is a high pressure over the sea, and there is a center of low pressure on the Eurasian continent, so it will move towards the northwest of Eurasia, and at the same time will be affected by geostrophic deflection forces.

Typhoons are not only strongest in summer, but also in autumn.

You can check the most serious typhoon since the founding of the People's Republic of China, and it is said that there is a typhoon with a wind speed of 90 meters per second.

There is also a Tomuro typhoon, this one is from Japan, and there are only a few reasons why you can go and see for yourself.

You can go to Wikipedia to check, ** there are more things, there are categories, it is easier to look.

A typhoon is a tropical cyclone called a hurricane in the Atlantic Ocean and a typhoon in the Pacific Ocean.

There are probably not as many typhoons in the Northwest Pacific as there are in the equatorial region, right?

From the structure of the typhoon, it can be seen that such a huge behemoth must have unique conditions for its generation:

It is necessary to have a vast surface of the hot ocean. (The Northwest Pacific Ocean is wide) the sea temperature should be higher than and 60 meters deep. Typhoons are a very violent weather system, consuming an average of 3,100 to 4,000 calorie centimeters of energy per day, a huge amount of energy that can only be achieved by the latent heat released by the vast tropical oceans**.

In addition, the warm water layer must be 60 meters thick to ensure that the sea surface temperature is always higher than that during the typhoon, the strong winds that swirl around the typhoon will cause the sea water to churn at a depth of 60 meters.

There must be a suitable flow field. The formation of a typhoon (ocean current, warm current) requires a strong upward movement. Suitable flow fields (e.g., easterly waves, equatorial convergence zones) are prone to tropical weak cyclones, and the pressure of tropical weak cyclones is low in the middle and high in the periphery, which promotes the continuous convergence of the airflow towards the center of the cyclone and its upward movement. During the ascent process, the condensation of water vapor releases a huge latent heat, which forms a warm heart to replenish the typhoon energy and makes the upward motion stronger and stronger.

There should be a sufficiently large geostrophic deflection force. If the convergence airflow reaches the center of the cyclone and there is a blockage of air accumulation, the typhoon cannot form. A sufficiently large geostrophic deflection force makes it difficult for the convergent airflow to flow directly into the center of the depression, but rotates along the center, strengthening the cyclonic circulation.

The geostrophic deflection force at the equator is zero, and gradually increases towards the poles, so the typhoon occurs about 5 degrees above the equator, between 5 20 degrees.

The direct shear of the lead in the airflow should be smaller. That is, there is not much difference between the wind direction and wind speed at high and low altitudes. If the difference between wind speed at high and low altitude is too large, the latent heat will quickly advection, which is not conducive to the formation and maintenance of the typhoon's warm heart. In areas with latitudes greater than 20 degrees, the upper level winds are very strong, which is not conducive to warming, and typhoons are not easy to appear.