Features of the formation of tropical typhoon hurricanes. Tropical cyclones, hurricanes, typhoons. What is the "Explosive deepening of the cyclone"

First hit full strength. The house is falling apart. I looked at the barometer, which showed 674.5 mm, dropped it into the water, and the wind blew me out into the sea.

I woke up in a tree and found myself stuck in the branches of a palm tree 20 feet above the ground.

“You can easily imagine my surprise, chagrin, ... when I saw the terrible state of the island of Barbados and the destructive power of the hurricane. The strongest buildings and entire blocks of houses, most of which were made of stone and distinguished by their solidity, yielded to the fury of the wind and were torn to the ground. Entire forts on the fortress were destroyed and many of the heavy cannons were carried over 100 feet from them. If I had not seen it myself, nothing would have made me believe it. More than six thousand people died, and all the dwellings were completely destroyed.” To this testimony of Admiral Rodney, then commander of the English fleet and an eyewitness to the "Great Hurricane" in the West Indies in 1780, one can only add that total number human casualties then amounted to more than twenty thou-. thousand Dozens of ships with the entire crew sank, the islands of Barbados, St. Lucia, Dominica, St. Vincent, Puerto Rico were completely devastated.

In some tropical regions of the world, the inhabitants of islands and coastal areas sometimes suffer terrible disasters caused by cyclones of small diameter, in which the wind speed in some cases exceeds 120 meters per second, and the amount of precipitation per day reaches 1000 - 12000 millimeters.

All cyclones originating in the tropics can be divided into four groups:

– tropical disturbance – area of ​​weak cyclonic circulation;

– tropical depression – a weak tropical cyclone with a pronounced surface circulation; the highest steady wind speed does not exceed 12.5 meters per second;

– tropical storm- a cyclone, the highest steady wind speed in which reaches 33 meters per second;

A tropical hurricane is a cyclone with wind speeds exceeding 33 meters per second.

Tropical hurricanes are called "typhoons" in Japan, "bagweese" in the Philippines, and "willy-willies" in Australia. All these names translated into Russian mean "big wind" or "strong wind".

There are several theories for the origin tropical hurricanes.

According to the convective theory, hurricanes arise due to the development of intense convective vertical air currents over the most heated parts of the ocean, at such a distance from the equator that the deflecting force of the Earth's rotation is able to impart a vortex motion to the air masses. The unstable thermal stratification of the atmosphere that often occurs in these areas contributes to the intensive rise of air supersaturated with water vapor. At the moment of steam condensation, a huge amount of latent heat of vaporization is released, which is converted into the kinetic energy of the cyclone.

In the central part of the cyclone, under the action of centrifugal ejection of air with a small inflow of air in the surface layer, the pressure drops rapidly. Initially, a weak depression of atmospheric pressure deepens, and after a few days a powerful cyclone begins to move to the west, increasingly increasing its depth and speed. The strength of the wind in it also increases. The cyclone develops into a tropical hurricane.

And, finally, the theory of the eastern wave explains the origin of hurricanes by the passage of a long (up to 2000 kilometers long) wave of atmospheric pressure. This wave, moving from east to west, loses its stability and turns into a whirlwind.

The average duration of a tropical hurricane ranges from 6 to 9 days. The longest hurricanes exist, originating near the coast of Africa and in the region of the Cape Verde Islands, twice crossing Atlantic Ocean and going far to the north. Their duration is 3 or 4 weeks. Sometimes tropical hurricanes turn into ordinary cyclones, and then the duration of their existence is enormous.

Thus, the hurricane of 1900, which killed 6,000 people in Galveston (USA) on September 8, began on August 27 in the mid-Atlantic, crossed the Caribbean Sea, the Gulf of Mexico and went deep into the continent. In the Great Lakes region, it transformed into an ordinary hurricane, but, retaining its strength, crossed North America, the Atlantic Ocean, Europe and went far into Siberia. The lifetime of this hurricane was 27 days.

At the surface of the earth, a hurricane is usually a nearly circular area of ​​storm and hurricane winds diameter up to 500, and in some cases - up to 1000 kilometers. Top speed winds, sometimes exceeding 80 meters per second, occur in the ring at a distance of 30 kilometers from the center low pressure. However, in some cases, destructive winds cover a wider area. For the Pacific Ocean, the average size of the destruction zones accompanying a typhoon reaches 40–80 kilometers at overall dimensions hurricane up to 1500 kilometers.

An amazing feature of tropical eddies is a high funnel (up to 10 - 14 kilometers) with steep sides rotating at a tremendous speed.

Here is how an observer from an airplane crossing a hurricane picturesquely talks about the central part of a typhoon: “We are in the wall of a typhoon, in the zone of maximum winds, in the zone of convergence - the convergence of air flows, where crumpled, oblique, squeezed winds madly rush towards a giant funnel of depression and cannot cross the mysterious border of the wall.

And suddenly, just as the Boeing seems to be caught in the final burst of elemental frenzy, there is a sudden silence.

This is the eye

This is the zone of the lowest pressure and the temperature of the highest...

It is an abyss, an abyss in the atmosphere, where, as if at the call of a prophet, fantastic hordes of millions of cubic meters of air rush, consumed by impatience and dizziness, burdened by heat, howling and whirling, raising the ocean in waves and foam, like road dust, thrown back, colliding with others. crowds seized by the same mystical madness of matter...

A wall stretches around, a fortress that seems to have been erected to make us prisoners of this country full of magical charm ... "

And here is an excerpt from P.A. Molan's Typhoon Chasers (1967):

“One should not think that a typhoon is clearly demarcated, that it looks like a millstone turning and grinding the earth to powder, or like a rotating column. It has no distinct boundaries - it is a vague mass twice the height of Everest, with a crater in the center, which can never be forgotten by anyone who has seen it at least once. This is a world of violent forces, a world of inevitable death, a world with an energy equal to the energy of three atomic bombs per second".

Indeed, the energy of tropical hurricanes is enormous.

In the homeland of hurricanes, in the tropics, air masses are very hot and saturated with water vapor - the temperature of the ocean surface at these latitudes reaches twenty-seven to twenty-eight degrees Celsius. As a result, powerful ascending currents of air arise and the release of the stored air solar heat and condensation of the vapors it contains. The process develops and grows, it turns out a kind of giant pump - into the funnel formed at the place of origin of this pump, neighboring masses of the same warm and vapor-saturated air are sucked in, and thus the process spreads further and in breadth, capturing more and more new areas on the surface of the ocean.

When you pour water from the bathtub through the drain hole, a whirlpool is formed. Approximately the same thing happens with the air rising up at the place where the cyclone originates - it begins to rotate.

The giant air pump continues to work, more moisture condensing on its funnel-shaped top, more heat being released. (American meteorologists have calculated that over a million tons of water can be lifted up in one day - in the form of steam, which continuously saturates the surface layer of the atmosphere; the energy released during condensation in just ten days would be enough for such a highly industrialized state, like the USA, for six years!). It is believed that a moderate cyclone releases approximately the same amount of energy as 500,000 atomic bombs with the power dropped over Hiroshima. Atmosphere pressure in the center of the emerging cyclone and on its outskirts becomes unequal: there, in the center of the cyclone, it is much lower, and a sharp pressure drop is the reason strong winds, which soon develop into hurricanes. In a space with a diameter of three hundred to five hundred kilometers, the strongest winds begin their frantic whirlwind.

Having arisen, cyclones begin to move at an average speed of 10-30 km / h, sometimes they can hover over the area for a while.

Cyclones (ordinary and tropical) are large-scale eddies with a diameter: ordinary from 1000 to 2000 km; tropical from 200 to 500 km and height from 2 to 20 km.

Air masses move in the area of ​​the cyclone in a spiral, twisting towards its center (counterclockwise in the northern hemisphere, vice versa in the southern) at a speed of:

Ordinary no more than 50-70 km / h;

Tropical 400-500 km/h

In the center of the cyclone, the air pressure is lower than at the periphery, which is why, moving in a spiral, the air masses tend to the center, where they then rise up, generating heavy clouds.

If in the center:

Normal cyclone air pressure compared to atmospheric (760 mm r.s.) is 713-720 mm r.s.;

Then in the center of a tropical cyclone, the pressure drops to 675 mm r.s.

At the center of a tropical cyclone there is an area of ​​low pressure with high temperature, with a diameter of 10-40 km, where calm reigns - typhoon eye.

Annually for globe At least 70 tropical cyclones arise and fully develop.

When a tropical cyclone (typhoon, hurricane) approaches the coast, it carries huge masses of water in front of it. Storm Shaft accompanied by strong rains and tornadoes. It swoops down on coastal areas, destroying everything in its path.

Example

In 1970, a typhoon. which broke through the mouth of the Ganges River (in India) flooded 800,000 km 2 of the coast. Had a wind speed of 200-250 m/s. Sea wave reached a height of 10 m. About 400,000 people died.

Today there are modern methods forecasting tropical cyclones (typhoons, hurricanes). Every suspicious cloud formation where it did not occur is photographed by meteorological satellites from space, weather service planes fly to the "eye of the typhoon" to get accurate data. This information is put into computers in order to calculate the path and duration of a tropical cyclone (typhoon, hurricane) and notify the population in advance of the danger.

Hurricane

A hurricane is a wind force of 12 points (up to 17 points) on the Beaufort scale, i.e. at a speed of 32.7 m/s (more than 105 km/h) and reaches up to 300 m/s (1194 km/h)

Hurricane– strong small scale atmospheric vortex, in which the air rotates at a speed of up to 100 m / s. It is shaped like a pillar (sometimes with a concave axis of rotation) with funnel-shaped extensions at the top and bottom. The air rotates counterclockwise and simultaneously rises in a spiral, drawing in dust, water, and various objects. A hurricane on land is called storm and on the sea storm.

The main characteristics of hurricanes are:

Wind speed;

Ways of movement;

Dimensions and construction;

Average duration of actions.

most important characteristic hurricanes is wind speed. The table below (on the Beaufort scale) shows the dependence of the wind speed and the names of the modes. The average speed of a hurricane in Ukraine is 50-60 km/h.

Hurricanes vary greatly in size. Usually, the width of the zone of catastrophic destruction, which can be measured in hundreds of kilometers, is taken as its width. The hurricane front reaches a length of up to 500 km. Hurricanes occur at any time of the year, but are more frequent from July to October. In the remaining 8 months they are rare, their paths are short.

The average duration of a hurricane is 9-12 days. In Ukraine, hurricanes do not last long, from a few seconds to several hours.

A hurricane is almost always clearly visible; when it approaches, a strong hum is heard.

Hurricanes are one of the most powerful forces elements. In terms of their harmful effects, they are not inferior to such terrible natural disasters as earthquakes. This is due to the fact that they carry enormous energy. Its amount released by a hurricane of average power in one hour is equal to the energy nuclear explosion at 36 Mgt.

A hurricane carries a triple threat to people who find themselves in its path. The most destructive are wind, waves and rain.

Often, showers accompanied by a hurricane are much more dangerous than the hurricane itself, especially for those people who live on or near the coast. A hurricane creates waves up to 30 m high on the coast, can cause showers, and later cause an epidemic, for example, a hurricane storm tide, which coincided with the usual one, caused a giant flood on the coast of India in 1876, during which the wave rose by 12-13 m About 100,000 people drowned and almost as many died from the consequences of a ferocious epidemic.

When a hurricane propagates over the sea, it causes huge waves 10-12 meters or more high, damaging or even leading to the death of the ship.

The greatest danger during a hurricane is objects lifted from the ground and spun to great speed. Unlike storms, a hurricane travels in a narrow band, so it can be avoided. You just need to determine the direction of its movement and move in the opposite direction.

Hurricane wind destroys strong and demolishes light structures, devastates sown fields, breaks wires and knocks down power lines and communication poles, damages highways and bridges, breaks and uproots trees, damages and sinks ships, causes accidents on utility and energy networks in production . There were cases when hurricane winds destroyed dams and dams, which led to large floods, threw trains off the rails, tore bridges from supports, knocked down factory pipes, and threw ships onto land.

The destructive activity of typhoons and hurricanes is carried out as a result of the combined action of the colossal force of the wind, the huge amount of precipitation, the stormy rise in the level of the ocean and the resulting giant waves.

The Beaufort scale for a unified assessment of the state of the sea from one (calm sea) to 12 points (hurricane - the sea is white from foam and waves reaching a height of 15 m) turned out to be unsuitable for characterizing wind speed during typhoons and hurricanes. To these 12 points, 5 more were added; the last 17 points corresponds to a wind speed of 460 km/h.

Modern instruments are not capable of registering wind speeds of more than 300 km/h. A record speed is considered to be approximately 400 km / h, which means not an instantaneous gust, but a wind blowing for 5 minutes. Separate gusts have a speed of 20 - 30% more.

In tropical cyclones, wind speeds often reach 300-400 km/h. Such speeds are not measurable. They are judged by the destruction that cyclones leave behind. These hurricanes often drop heavy rain and hail. Waterfalls falling from the sky and accompanied by the roar of the wind are terrifying. Cases are known when, in areas of future typhoons, the surfaces of bays were covered with dead fish who died from excess fresh water.

Tropical cyclones on the way of movement cause huge material damage and take away a lot of human lives.

The inhabitants of the Philippine Islands, Indochina and Japan have known the word "typhoon" since time immemorial. Typhoons in the Bay of Bengal have many victims. They contribute to the occurrence of storm floods that inundate low-lying, densely populated coasts.

There are cases when one typhoon claimed thousands of human lives, for example, typhoon Vera in September 1959 killed 5,500 people. This number will increase significantly if we take into account people who died later from starvation and disease.

The damage inflicted material values, can be conditionally divided into direct and indirect. Direct is the damage that manifests itself directly during the action of the storm (destruction of buildings, fires, loss of crops, etc.). Indirect damage is damage that manifests itself for a long time after the passage of typhoons and hurricanes over islands and continents. For example, the absence of a crop for several years in those fields from which the surface layer of soil was carried away, a reduction in production in destroyed factories and factories. The amount of indirect damage caused by a tropical cyclone can be several times greater than the amount of direct damage. Long-term statistics of observations of tropical cyclones made it possible to identify some patterns that relate the amount of damage caused to the physical characteristics of tropical cyclones. This allows you to get a rough idea of ​​the scale of the impending disaster.

biological significance cyclones lies in their ability to carry seeds of plants, and sometimes rather large animals, over great distances. Apparently, it was these winds that contributed to the settlement of many volcanic and coral islands that arose in the expanses of the oceans, and the migration of plants and animals. The hurricane of 1865 brought pelicans to Guadeloupe, previously unknown there.

The famous Great Hurricane in October 1780 destroyed the city of Savannah-la-Mar (Georgia, USA). According to an eyewitness, the inhabitants were petrified with amazement when they saw the approach of an unprecedented wave; sweeping away all obstacles with one gigantic squall, it flooded the city and demolished everything and everything. Seven days later the storm reached maximum strength. She completely devastated the island of St. Lucia, where 6,000 people died under the ruins, and sank the English fleet anchored off the island. The sea here rose so high that it flooded the fleet and, bringing the ship on the crest of one of its giant waves, threw it onto the naval hospital, destroying the building with the weight of the ship. The hurricane then headed for the island of Martinique, where 40 French transport ships carrying 4,000 soldiers were sunk. The islands of Dominica, St. Eustatius, St. Vincent, Puerto Rico, located to the north, were also devastated and sunk big number ships caught in the path of a cyclone.

On the night of November 13, 1970, an incredible typhoon hit the coastal regions of East Pakistan (since 1971 People's Republic Bangladesh). A powerful wave up to 8 m high, raised by the wind, passed over a chain of densely populated islands. It was colossal water wall, boiling and seething, a huge shaft of water that the ocean threw out. Sweeping away everything in its path, it hit the coast and, together with a hurricane wind, brought catastrophic destruction. For several hours, these islands and part of the mainland coast were under water. The consequences of the typhoon are catastrophic: bridges were torn down, highways and railways were destroyed, entire villages were completely destroyed along with the inhabitants. More than 10 million people were affected by the typhoon, according to newspaper reports. The death toll exceeded half a million, and according to some sources, about a million people. One of the most powerful natural disasters in the history of mankind has happened.

An extraordinary hurricane hit 11 states in 1974 North America. Sowing death and destruction, the hurricane and its accompanying tornadoes in 8 hours left on their way, according to published data, 350 killed, thousands of wounded and missing. In the states of Illinois, Indiana, Ohio, Kentucky, West Virginia, Virginia, Tennessee, North Carolina, Alabama and Georgia, hundreds of houses and shops, schools, hospitals and churches were destroyed. Property damage, according to incomplete data, is estimated at $ 1 billion. Among the most severely affected by the hurricane is the city of Zinia in Ohio. According to eyewitnesses, the hurricane hit suddenly around 5 o'clock. evening, rumbled like a passenger train rushing at great speed. In a city of 25,000, more than 70% of buildings were completely or partially destroyed, including the state university. The city of Brandenberg ceased to exist. In Alabama, the cities of Jasper and Guin are razed to the ground.

On the eve of 1975, tropical cyclone "Tracy" almost completely destroyed the capital of the northern territory of Australia, Darwin - a city with a population of 44 thousand people. The wind force reached a speed of 260 km / h. The hurricane tore roofs off houses like balls, tossed tourist buses through the streets. Numerous cottages fell apart under the pressure of the wind, like houses of cards. But administrative buildings and high-rise hotels turned out to be hardly more stable. Turned into mountains of rubble and debris business center Darwin. A large naval base located near the city was destroyed. Several ships sank.

In 1980, during August and September 1980 alone, four events of tropical cyclone development were noted in the northern hemisphere and southern hemisphere- one case, of which two were hurricanes in the Caribbean and three were typhoons in the Pacific.

Hurricane Alley was recorded in early August off the coast of Haiti and Jamaica. The wind speed in it reached 70 m/s. The second hurricane, Ermina, was observed in the 20th of September off the northern coast of Honduras, as well as off the coast of Mexico and Guatemala. The wind speed in it reached 30 m/s.

Typhoon Orchid originated in the Western Pacific Ocean and swept over the Japanese Islands on September 11-12 and South Korea causing significant damage and flooding. The influence of this typhoon became noticeable days later in the Khabarovsk and Primorsky Territories and on Sakhalin. Observed heavy rains and wind, wind speed in some places reached hurricane (33 m/s). About a month later, in mid-October, another typhoon came to the Japanese islands of Kyushu and Shikoku from the south, temporarily disrupting not only air, but also railway communication.

At the beginning of the third decade of September, Typhoon Kei appeared in the southeastern Pacific Ocean, in the center of which the wind speed reached 30-40 m/s.

There were tropical cyclones in subsequent years, both in the northern and southern hemispheres. In particular, tropical cyclones Eilena, which hit the Comoros in the Indian Ocean on January 10, 1983, and Andri, which caused great destruction on the northwestern coast of the island of Madagascar in the Indian Ocean, turned out to be very destructive.

The year 1985 was also a fruitful year for tropical cyclones: seven tropical cyclones - typhoons passed in the South China Sea during the summer and autumn of this year, causing catastrophic floods and human casualties in the coastal regions of Vietnam and China.

One of the typhoons, Lee, penetrated far north to the Korean Peninsula and, turning into an ordinary cyclone, brought with it heavy rains to the territory of the Soviet Primorye in mid-August.

Another typhoon on September 10-12 destroyed a third of the fruit crop and caused damage to about 90% of the cultivated area on the Japanese island of Honshu.

In late October, Typhoon Saling claimed the lives of more than 60 residents of the island of Luzon in the Philippines and caused more than 700 million pesos of damage to the island's farms. Almost simultaneously in the other hemisphere, in the Gulf of Mexico, another tropical cyclone arose - Hurricane Juan, which severely affected the inhabitants of several coastal states of the United States, and a month later - Hurricane Keith, which caused flooding and significant destruction in northern Cuba and the United States. Hurricane Keith in terms of intensity and extent of damage caused by about. Cuba and the coast of the Florida peninsula proved to be one of the most ferocious in the last 50 years; gusts of wind and ocean waves running ashore destroyed many thousands of houses, more than a million people had to be evacuated from disaster zones, and there were human casualties.

Tropical Cyclone Jeanne (September 2004) -- Caribbean Sea, Haiti. The death toll from heavy rains, floods and landslides on the island of Haiti caused by Hurricane Jeanne could reach 2,000, the Associated Press reported. As of September 23, almost 1,100 victims are already known, and another 1,250 people are missing. Most a large number of victims - in the city of Gonaives in the northern part of the island. According to authorities, 1,013 people died here. Representatives of the Red Cross fear the spread of epidemics through the water, in which the bodies of drowned people were located for several days. The water level in some places exceeds four meters, and as it declines, more and more victims are found. The President of Haiti called what is happening a humanitarian catastrophe and asked international community about help. In May 2004, the island had already suffered one of its most terrible floods over the entire history, as a result of which about 2.5 thousand people died.

Hurricane Katrina is one of the most destructive hurricanes in US history. As a result of the natural disaster, 1,836 residents died, and the economic damage amounted to $81.2 billion. physical characteristics. Before it reached the coast of the United States, it was assigned a level 5 hurricane scale on the Saffir-Simpson Hurricane Scale. Fortunately, about 12 hours before landfall, the hurricane weakened to a Category 4 level. The wind speed during the hurricane reached up to 280 km / h (according to other reports 62 m / s (? 223 km / h). August 27, 2005 passed over the coast of Florida near Miami and turned towards the Gulf of Mexico. August 29, 2005 reached south- east coast of the United States in the Louisiana and Mississippi region. Due to the location below sea level, many cities of the southeast coast of the United States were flooded. In New Orleans, this happened with 80% of the city, many buildings collapsed. Economic damage amounted to $ 125 billion. ( estimate, 2007).About 800,000 people were left without electricity and telephone service.The officially confirmed number of victims was 1407 people, according to later data 1600, of which more than 720 were in New Orleans; in addition, as of December 2005, 47 people were missing More than a quarter of the population of New Orleans (150 thousand people) still have not returned to the city (August 2006).

March 14, 2007 Madagascar again experienced the blow of the elements. Another tropical cyclone, Indlala, reached the northeast coast of the island, reaching category 3 in strength. The wind speed in this cyclone reached 115 knots with gusts up to 140 knots. Reportedly news agencies, over the past days, this cyclone claimed the lives of 36 people, 53 thousand 750 people were left homeless. Since December 2006, Indlala has become the fourth cyclone to hit Madagascar. On March 19, 2007, he left the island. While devastating floods are observed in the north of the island due to powerful cyclones, its southern part endures drought and famine. Cyclone season in the south indian ocean usually lasts from November to March. But the 2006/07 season differs from the previous ones in greater activity.

On October 7, 2008, Mexico was literally in the grip of tropical cyclones. Tropical Storm Marco has formed in the Gulf of Mexico. Wind gusts reached 27 m/s. Storm "Marco" came close to the coast. Brought torrential rains. On the other side of Mexico, over the water area Pacific Ocean, another cyclone is Hurricane Norbert.

Lecture plan

The concept of a tropical cyclone.

Origin and structure of tropical cyclones.

Areas of origin and main paths of tropical cyclones.

Development stages and trajectories of tropical cyclones.

Weather in tropical cyclones.

Signs of an approaching tropical cyclone.

Determination of the ship's position relative to the center of a tropical cyclone.

Basic theoretical provisions

The concept of a tropical cyclone.

Cyclonic activity is observed not only in temperate and high latitudes Oh. Near the tropical fronts of both hemispheres (in the latitudinal zone from 5 to 25° N and S), menacing natural phenomena, mesoscale vortices, or tropical cyclones arise on the Earth. Usually, a large number of cyclonic disturbances occur at low latitudes, but they are weakly expressed: the pressure in the center is only 1–2 mbar below the surrounding baric field, the winds are weak, and move slowly from east to west. But from time to time these disturbances begin to develop and turn into deep tropical cyclones with large baric gradients and storm winds. They are related to frontal cyclones of temperate and high latitudes by storm and hurricane winds, similar rotational circulation of eddies, abundant precipitation falling from their cloud systems, and proportionality.

The fundamental differences between frontal and tropical cyclones are in their energy, vertical structure of air flows, wind speed, direction of movement and lifetime of the eddies themselves.

Tropical cyclones are relatively small but very deep eddies with high kinetic energy. For the development of a tropical cyclone, a large energy of air mass instability is required. A powerful rise of very warm and humid air above the perturbation that has arisen is a necessary condition for its development.

The pressure at the center of a tropical cyclone is usually 980–950 mbar, in some cases below 930 mbar. A tropical cyclone is 100–300 miles in diameter, but sometimes more.

2. Origin and structure of tropical cyclones.

Due to the colossal energies (in some cases, the wind speed in hurricanes exceeds 120-150 m/s), the amount of precipitation falling per day reaches a height of 20 m or more.

In the central part of the hurricane, under the action of centrifugal ejection of air, with a small inflow of air in the surface layer, the pressure drops rapidly. Initially, a weak baric depression intensifies, and after a few days a powerful cyclone begins to move to the west, increasing its depth and speed of movement more and more, and the strength of the wind in it also increases. The cyclone develops into a tropical hurricane.

According to frontal theory, the occurrence of a hurricane is explained by the interaction air masses Northern and Southern hemispheres on the tropical front in the trade winds meeting zone. Here, due to the intensive heating of the ocean surface, there is a significant contrast in the temperatures of the lower and upper layers of the atmosphere, which creates a great instability of air masses - powerful convective movements.

wave theory The origin of hurricanes is trying to connect the passage of long (up to 2000 km) eastern waves of atmospheric pressure. These waves, moving from east to west, lose their stability and turn into eddies - tropical cyclones.

There are four stages in the development of any tropical cyclone to an intense hurricane:

- stage of formation- unstable weather, squally winds of various directions. The center of the cyclone is outlined. The wind strength near it (50-100 nautical miles) does not exceed 7 points;

- young cyclone– further pressure drop, formation of a belt of hurricane winds around the center of the cyclone. Formation in the center of the cyclone of clear weather with light winds or calm - "eyes of the storm";

- mature hurricane– cessation of pressure drop and wind increase. The area occupied by the hurricane increases to a maximum, the symmetry of the hurricane is broken. Bad weather in its right half it is observed on a larger area than in the left.

- hurricane destruction. This stage occurs, as a rule, after the hurricane turns through the polar course to the east. The intensity of the hurricane weakens, the "eye of the storm" disappears and the hurricane takes on the features of an ordinary non-tropical (frontal) cyclone. In the same way, tropical hurricanes also die out when they move to land, when the influx of moisture stops and air friction against the underlying surface increases.

All cyclones originating in the tropics are divided into four groups.

1st group. Tropical disturbance - has a weak tropical circulation.;

2nd group. Tropical depression - a weak tropical cyclone with a pronounced surface circulation, the highest steady wind speed in which does not exceed 12-13 m/s;

3rd group. A tropical storm is a cyclone, in which the highest steady wind speed reaches 33 m/s;

4th group. A tropical hurricane is a cyclone in which wind speeds exceed 33 m/s (60 kt).

Thus, tropical cyclones are classified as follows (Table 1)

The classification is based on the criterion of wind speed in the central region of a tropical cyclone. However, tropical cyclones differ not only in the wind regime, but also in the nature of the distribution of clouds, precipitation, and other meteorological elements (Table 1).

Table 1. Classification of tropical cyclones depending on wind speed.