What is a tropical cyclone. Tropical cyclones

The destructive power of cyclones, typhoons and hurricanes lies primarily in the colossal wind speed that affects the land and causes waves at sea. The destructive effect of cyclones is associated with the turbulent, vortex movement of air particles. Destruction during cyclones is also associated with low pressure in their center-eye. Extremely heavy rain showers, which cause floods, are also detrimental.

Tropical cyclones occur in tropical latitudes. They are distinguished by a clear concentration of energy in a small space, large pressure drops and high wind speeds. Annually over earth's surface 70-80 tropical cyclones are formed in total, but only a small part of them reaches destructive power, and of these, in turn, only a part captures the land.

According to the definitions, the wind speed in tropical cyclones should exceed 34 m/s. However, most of them are characterized by speeds much higher than 50 m/s, and speeds of more than 100 m/s (that is, more than 360 km/h) have been recorded.

Consider the structure of a tropical cyclone. The diameter of its inner part - the eye, where calm reigns and the sky is clear, most often fluctuates between 10 and 20 km. The eye is surrounded by a so-called wall where the winds reach top speed. In the wall, not only vortex, but also ascending air movements are carried out. Part of the air in the marginal zones of the cyclone is drawn in, the other part is released.

Tropical cyclones are born all the time. This happens near the equator, most often in the band between 5 and 10 ° north or south latitude.

Cyclones most often move at a speed of 30-50 km/h. In the Atlantic and Pacific oceans, they first move to the west, then turn to the north and northeast. Over land, their tracks become irregular: they turn, turn back and cross their track. Such cyclones are especially dangerous. They are called wanderers. Cyclone Flora also belonged to this type, which in 1963 devastated eastern part Cuba. East Asian cyclones (typhoons) first move due west and turn north near land. Cyclones in the Bay of Bengal move in a northwesterly direction directly over land.

The energy of tropical cyclones is colossal, it is difficult to accurately calculate it. It is believed that a medium-strength cyclone releases approximately the same amount of energy as 50,000 atomic bombs with a capacity of 30 kilotons. The ocean and moist air are needed by the cyclone as energy suppliers. The vapor rises, the pressure at altitude drops, and the vapor condenses. This condensation is the main source of energy that keeps the cyclone alive.

Hurricanes these are winds of force 12 on the Beaufort scale, i.e. winds exceeding 32.6 m/s (117.3 km/h).

Hurricanes occur during the passage of deep cyclones and represent the movement air masses(wind) at great speed. During a hurricane, the air speed exceeds 32.7 m/s (more than 118 km/h). Sweeping over the earth's surface, the hurricane breaks and uproots trees, rips off roofs and destroys houses, power lines and communications, buildings and structures, disables various equipment. As a result of a short circuit in the power grid, fires occur, the supply of electricity is disrupted, the operation of objects stops, and other harmful consequences may occur. People may find themselves under the rubble of destroyed buildings and structures. Flying with high speed fragments of destroyed buildings and structures and other objects can cause serious injuries to people.

Reaching the highest stage, the hurricane goes through 4 stages in its development: tropical cyclone, baric depression, storm, intense hurricane.

Hurricanes typically move at 15 km per hour along a westerly path and often pick up speed, usually veering toward north pole on the line 20-30 degrees northern latitude. But often they follow a more complex and unpredictable pattern. In any case, hurricanes can cause enormous destruction and tremendous loss of life.

Modern methods weather forecasts allow several hours or even days to warn the population of a city or an entire coastal region about an impending hurricane (storm), and the civil defense service can provide necessary information about the possible situation and actions in the current conditions.

When propagating over the sea, a hurricane causes huge waves with a height of 10-12 m or more, damages or even leads to the death of the ship.

After a hurricane, NASF, together with the entire able-bodied population of the facility, carry out rescue and emergency recovery work; rescue people from collapsed protective and other structures and provide assistance to them, restore damaged buildings, power and communication lines, gas and water pipelines, repair equipment, and carry out other emergency recovery work.

Tornadoes.

A tornado is one of the cruel, destructive phenomena of nature. According to V.V. Kushina, tornado - this is not wind, but a “trunk” of rain twisted into a thin-walled pipe, which rotates around its axis at a speed of 300-500 km / h. Due to centrifugal forces, a vacuum is created inside the pipe and the pressure drops to 0.3 atm. If the wall of the "trunk" of the funnel breaks, bumping into an obstacle, then outside air rushes into the funnel. Pressure drop 0.5 atm. accelerates the air secondary flow to speeds of 330 m/s (1200 km/h) and more, i.е. to supersonic speeds. Tornadoes are formed in an unstable state of the atmosphere, when the air in the upper layers is very cold, and in the lower layers it is warm. There is an intense air exchange, accompanied by the formation of a vortex of great strength.

Such whirlwinds arise in powerful thunderclouds and are often accompanied by thunderstorms, rain, and hail. Obviously, it cannot be said that tornadoes arise in every thundercloud. As a rule, this happens on the verge of fronts - in the transition zone between warm and cold air masses. It is not yet possible to predict tornadoes, and therefore their appearance is unexpected.

The tornado does not live long, since rather soon the cold and warm air masses mix, and thus the reason supporting it disappears. However, even in a short period of its life, a tornado can cause enormous damage.

Until now, the tornado is in no hurry to reveal its other secrets. So, there are no answers to many questions. What is a tornado funnel? What gives its walls a strong rotation and tremendous destructive power? Why is the tornado stable?

To study a tornado is not only difficult, but also dangerous - upon direct contact, it destroys not only the measuring equipment, but also the observer.

Comparing the descriptions of tornadoes (tornadoes) of the past and present centuries in Russia and other countries, one can see that they develop and live according to the same laws, but these laws have not been fully elucidated and the behavior of a tornado seems unpredictable.

During the passage of tornadoes, of course, everyone hides, runs, and people are not up to observing, and even more so measuring the parameters of tornadoes. That little about internal structure funnels, which we managed to find out, is due to the fact that the tornado, breaking away from the ground, passed over the heads of people, and then it was possible to see that the tornado is a huge hollow cylinder, brightly lit inside by the brilliance of lightning. A deafening roar and buzzing is heard from within. It is believed that the wind speed in the walls of the tornado reaches the sound.

A tornado can suck in and lift up a large portion of snow, sand, etc. As soon as the speed of snowflakes or grains of sand reaches a critical value, they will be thrown out through the wall and can form a kind of case or cover around the tornado. characteristic feature This case-cover is that the distance from it to the wall of the tornado along the entire height is approximately the same.

Meteorological natural disasters are very dangerous, as they entail huge human casualties, a good example of this is the hurricane Katrina in the United States, they are associated with the destruction of buildings, structures, cause great damage to humanity, which, of course, is a global problem.

Tropical cyclones

Tropical cyclones carry colossal reserves of energy and have great destructive power. Kinetic energy a medium-sized cyclone is comparable to the explosion energy of several powerful hydrogen bombs and accounts for about 10% of the total kinetic energy northern hemisphere.

Despite the fact that most countries have a warning system for tropical cyclones, the passage of each of them is accompanied by undesirable consequences for humans. Human casualties and huge material damage are associated with hurricane winds, floods caused by heavy downpours, as well as storm surges of water (surge - the rise of water along the coast when a cyclone moves to land, can reach 8 m or more).

One of the most destructive hurricanes "MITCH" in October 1998 killed 10,000 people in Honduras and Nicaragua and left 2 million homeless. These countries experienced the worst floods in 200 years. The total economic damage caused by the hurricane exceeded $5 billion.

Areas where tropical cyclones originate

Tropical cyclones can occur at any time of the year in the tropical parts of all oceans except the southeast Pacific and the southern Atlantic. Most often they are formed in the northern part of the tropical zone of the Pacific Ocean: here, on average, about 30 cyclones are traced per year. The main season for the development of tropical cyclones is August - September, in winter and spring their frequency is very insignificant.

Most often (in 87% of cases) tropical cyclones occur between latitudes 5° and 20°. At higher latitudes, they occur only in 13% of cases. The occurrence of cyclones north of 35° north latitude and south of 22° south latitude has never been noted. Tropical cyclones that have reached significant intensity in each region have their own name. In the eastern part of the Pacific Ocean and in the Atlantic they are called hurricanes (from the Spanish word "uracan" or the English "hurricane"), in the countries of the Hindustan Peninsula - cyclones or storms, in the Far East - typhoons (from the Chinese word "tai", which means strong wind). There are also less common local names: "willy-willy" - in Australia, "willy-wow" - in Oceania and "baguio" - in the Philippines.

Pacific typhoons and Atlantic hurricanes are named according to established lists. For typhoons four lists of names are used, one is installed for hurricanes. Each typhoon or hurricane that formed in a given calendar year, in addition to the name, is assigned a serial number of a two-digit year: for example, 0115, which means the fifteenth typhoon number in 2001.

Causes and evolution of tropical cyclones

Tropical cyclones form where observed heat water surface(above 26°), and the water-air temperature difference is more than 2°. This leads to an increase in evaporation, an increase in the moisture content in the air, which to a certain extent determines the accumulation of thermal energy in the atmosphere and contributes to the vertical rise of air. The emerging powerful thrust carries away more and more volumes of air, heated and moistened above the water surface. The rotation of the Earth gives the rise of air a vortex motion, and the vortex becomes like a giant top, the energy of which is grandiose.

The central part of the funnel is called " eye of the storm". This is a phenomenal phenomenon that amazes with the peculiarities of its “behavior”. When the eye of the storm is well defined, precipitation suddenly stops at its border, the sky clears up, and the wind weakens significantly, sometimes to calm. The shape of the eye of the storm can be very different, it is constantly changing. Sometimes there is even a double eye. The average eye diameter of a storm in well-developed cyclones is 10–25 km, while in destructive cyclones it is 60–70 km.

Tropical cyclones are named according to their intensity.:

1. Tropical disturbance - wind speeds are small (less than 17 m/s).

2. Tropical depression - wind speed reaches 17 - 20 m/s.

3. Tropical storm - wind speed up to 38 m/s.

4. Typhoon (hurricane) - wind speed exceeds 39 m/s.

AT life cycle A tropical cyclone can be divided into four stages.

1. Stage of formation. It begins with the appearance of the first closed isobar (an isobar is a line of equal pressure). The pressure in the center of the cyclone drops to 990 hPa. Only about 10% of tropical depressions develop further.

2. Stage young cyclone or stage of development. The cyclone begins to deepen rapidly; there is a significant drop in pressure. Hurricane force winds form a ring around the center with a radius of 40 - 50 km.

3. Stage of maturity. The pressure drop in the center of the cyclone and the increase in wind speed gradually stop. The area of ​​storm winds and intense showers is increasing in size. The diameter of tropical cyclones in the development stage and in the mature stage can vary from 60 - 70 km to 1000 km.

4. Stage of attenuation. The beginning of the filling of the pressure growth cyclone in its center). Attenuation occurs when a tropical cyclone moves into an area of ​​more low temperatures surface of the water or when moving to land. This is due to a decrease in the influx of energy (heat and moisture) from the surface of the ocean, and when it comes to land, it is also due to an increase in friction against the underlying surface.

After entering the temperate latitudes, a tropical cyclone may lose its specific properties and turn into an ordinary cyclone of extratropical latitudes. It also happens that tropical cyclones, remaining in the tropics, go to the mainland. Here they quickly fill up, but at the same time they manage to produce a lot of destruction.

Typhoons

Typhoons are among the most powerful and destructive tropical cyclones. Annual losses from typhoons cause significant damage to the economies of several Asian countries. Most economically underdeveloped countries have great difficulty repairing the damage caused by typhoons.

Of the 25-30 typhoons that appear each year over the Western Pacific Ocean, the Sea of ​​Japan and Primorsky Krai come out in different years from 1 to 4. All of them occur over the ocean northeast of the Philippines. Average duration of a typhoon is 11 days, and the maximum is 18 days. Minimum pressure, observed in such tropical cyclones, varies widely: from 885 to 980 hPa, but when typhoons enter our territory, the pressure in their centers rises to 960-1005 hPa. Maximum daily precipitation totals reach 400 mm, and wind speed - 20 - 35 m / s.

Archived article from #6(42) 2005

Tropical cyclones are one of the most amazing and, at the same time, formidable and destructive natural phenomena on Earth, rampaging over the tropical waters of all oceans, with the exception of the southern Atlantic and the southeast Pacific.

On our planet, on average, about 80 tropical cyclones are observed per year.

Intense tropical cyclones in each region have their own name. In the Atlantic and the Pacific Northeast they are called hurricanes; in the Pacific Northwest - by typhoons; in the Arabian Sea and the Bay of Bengal - cyclones; in the southern part indian ocean- orkans; off the coast of Australia - willy-willy; in Oceania - willy-wow; in the Philippines - baguio.

Tropical cyclones are huge eddies, reaching a diameter of 1000-1500 km and extending through the entire thickness of the troposphere. Distinctive feature tropical cyclones - a significant drop in pressure over short distances, which leads to the formation of hurricane-force winds. The pressure in the center of developed cyclones is about 950-960 hPa (the minimum of the recorded ones is 855 hPa).

Tropical cyclones occur over warm oceanic waters in the tropics of both hemispheres in the latitude zone 5-20°. They are a formidable product of the interaction of the ocean and the atmosphere.

Most tropical cyclones form in the interior tropical zone convergence - the zone of convergence of the trade winds of the two hemispheres, or trade winds, and equatorial western winds. Such a convergence zone is characterized by the presence of disturbances of varying intensity - some of them reach the stage of tropical depressions, some of which, under favorable conditions, develop into a tropical storm and hurricane. What contributes to the origin and further intensification of a tropical cyclone? First of all, this is the presence of an initial disturbance and a slight horizontal wind shear between the lower and upper troposphere. To create the “twisting” effect, a sufficient value of the Coriolis force, due to the rotation of the Earth around its axis, is necessary - tropical cyclones do not form near the equator, where the horizontal component of this force is zero. One of the conditions for the formation of tropical cyclones is the presence of humid unstable air and the development of convection.

Finally, this is the existence of an energy source - the thermal potential of the ocean. Simply put, tropical cyclones form over the ocean when its surface temperature exceeds 26°C. The ocean supplies a significant portion of the heat needed to maintain low pressure at the center of the cyclone. With an increase in water temperature, evaporation increases and the flow of the so-called latent heat increases, which forms a warm core in the middle troposphere, causing sharp decline pressure at the center of a tropical cyclone. A tropical cyclone can be thought of as a heat engine, whose work is connected with the ocean as a source of energy and as a trigger mechanism - the initial vortex is formed over the overheated region of the ocean. In addition, the thermal state of the ocean also affects the trajectory of tropical cyclones. But at the same time, the evolution of tropical cyclones is also determined by various atmospheric processes. We are dealing with a complex complex of ocean-atmosphere interactions.

A mature tropical cyclone is a powerful atmospheric vortex, which is characterized by large pressure gradients (drops) and, consequently, hurricane-force winds - up to 90 m/s, with the belt of maximum winds located between 20 and 50 km from the center. In tropical cyclones, powerful cloudiness develops, the amount of precipitation can reach 2500 mm per day. In well-developed cyclones, a phenomenal phenomenon is observed - the eye of the storm - an area where the sky clears up, the wind weakens, sometimes to calm, and precipitation suddenly stops at its border. The eye is surrounded by a wall of powerful clouds. satellite imagery discovered the existence of "hot towers" - high-altitude zones rain clouds, which are located above the "walls" of this very "eye" are much higher than the main part of the hurricane. "Towers" extend to the very "ceiling" - the upper layers of the troposphere. According to experts, "hot towers" play a key role in the process of amplifying the power of a hurricane. By the way, such “towers” ​​were also discovered in Hurricane Katrina. The appearance of the eye of the storm is associated with an increase in centrifugal force as it approaches the center of the cyclone. The average diameter of the "eye" is 20-25 km, in destructive hurricanes and typhoons it is 60-70 km. There are also two-eyed tropical cyclones.

The energy of a tropical cyclone is very high; according to experts, an average tropical cyclone generates an amount of energy equal to several thousand atomic bombs.

In three weeks, a hurricane generates energy comparable to what our Bratsk hydroelectric power station would have generated in 26,000 years. Humanity is not yet able to use this energy, nor to receive it in such quantity from any other sources.

The resulting tropical cyclone first moves from east to west, gradually deviating to higher latitudes: in the northern hemisphere - to the northwest. But if the cyclone reaches 20-30° latitude above the ocean, it begins to go around the subtropical anticyclone and its direction changes to the northeast. Such a point of the trajectory is called a turning point. Trajectories of movement of cyclones are mostly curvilinear, sometimes even "loops" appear. average speed The movement of tropical cyclones within the tropics is only 10-20 km/h. Coming out on land or in middle latitudes, a tropical cyclone fades or turns into an intense cyclone temperate latitudes. The Russian Primorye in the summer-autumn period is often exposed to such cyclones - former typhoons that bring abnormal precipitation and hurricane winds. So, in 1973, a typhoon that hit Primorye brought more than half of the annual precipitation to Vladivostok. The author of the article experienced all the "charms" of the raging elements, when in August 1979 Typhoon Irving hit Far East, flooding the Primorsky and Khabarovsk Territories.

In hydrometeorological practice, depending on wind speed, tropical disturbances are divided into tropical depression, tropical storm, severe tropical storm, tropical cyclone, typhoon, hurricane. In turn, the latter are divided into five categories (the Saffir-Simson hurricane scale) depending on the wind speed. The fifth category includes hurricanes with speeds exceeding 70 m/s.

Tropical cyclones that become tropical hurricanes get their names. This tradition dates back to World War II, when US Air Force and Navy meteorologists monitored typhoons and, to avoid confusion, named typhoons after their wives or girlfriends. After the war, the US National Weather Service compiled alphabetical list female names in order to facilitate communication and avoid embarrassment in the development of several cyclones in the region. When, in 1979, the real essence of the strong half of humanity was finally understood, the World Meteorological Organization (WMO), together with the US National Weather Service, included in the list and male names. Justice has prevailed. (Not all evil is from a woman!) These lists are constantly used and pre-compiled for each year and each region. However, in the event that a tropical cyclone is particularly destructive, the name given to it is struck off the list and replaced by another. So we can say quite definitely - we will never hear about a hurricane named "Katrina" again.

The destructive effect of tropical cyclones is due to hurricane-force winds, the deadly streams of water that hit the coast with the arrival of a hurricane - up to 20 million tons of water per day. For example, in January 1966, tropical cyclone Denis swept over Reunion Island in the Indian Ocean, bringing an incredible amount of rainfall - 182 centimeters per day. Added to the rainfall is "storm surge" - a rise in sea level that reaches 10 m in extreme cases. Storm surge floods are the most devastating effects of hurricanes. In 1970, Cyclone Ada in the Indian Ocean flooded the low-lying coast of Bangladesh with surge waves. More than 300 thousand people died then. Hurricane Hugo in 1989 brought down a wall of water 6 meters high on South Carolina. Such a blow can destroy buildings, roads, wash out the coast.

In the northern hemisphere, the "hurricane" season lasts, on average, from May to November. The longest period of development of tropical cyclogenesis is observed in the western Pacific Ocean. According to the Hydrometeorological Center of Russia, where a database of data on tropical cyclones is collected throughout the globe, an average of 26 tropical cyclones form in the western Pacific Ocean. In the Atlantic, the peak of hurricanes falls on August-September and there are about 9-10 cyclones per year. Research scientists have shown that in recent decades tropical cyclone activity increased in the Atlantic. So, from 1970 to 1979 their number was 81, from 1980 to 1989 - 96, from 1990 to 1999 - 105; moreover, 19 tropical cyclones were recorded in 1995 (the record still remains for 1933, when 21 cyclones formed in the Atlantic). According to the forecasts of American scientists, this trend will continue in the first decades of the 21st century, and this year 2005 may already break all records. This is primarily due to rising ocean surface temperatures. As satellite data showed, in 2005 the water surface temperature in the Atlantic basin increased by 2-4°C on average compared to previous years.

Until recently, the record holder among the Atlantic cyclones was Hurricane Andrew, which swept over the states of Florida and Louisiana in late August 1992 and caused $ 25 billion in damage. The minimum pressure in its center dropped to 923 hPa, and the wind speed reached 76 m/s.

However, Katrina, apparently, turned out to be a record holder in its parameters: the minimum pressure in its center was 902 hPa, while the wind speed at the same time exceeded 75 m/s (gusts up to 90 m/s). Katrina was born on August 23, 2005, east of Bahamas and, passing through southern Florida and intensifying in the Gulf of Mexico, where the water temperature exceeded 31 ° C, hit New Orleans on August 29, 2005, destroying dams and completely flooding the city. The death toll exceeded a thousand people, and the economic damage amounted to tens of billions of dollars. It was the most destructive hurricane ever to hit the coast of North America.

Following Katrina, Rita rushed to the coast of the United States, becoming the seventeenth tropical storm of the 2005 hurricane season.

Fortunately, she weakened before causing colossal harm. Both Katrina and Rita originated north of normal latitudes, where Atlantic tropical cyclones swirl. But the most unusual for the Atlantic was the twentieth hurricane named Vince. He managed to spin in the area of ​​the Azores, which is much north (30-35 parallel) of the usual area of ​​​​their formation. True, he failed to achieve high intensity and, having reached the first category, Vince quickly weakened to a tropical storm.

Tropical cyclones significantly redistribute energy in the atmosphere and therefore, despite their "compact" size, they affect atmospheric processes far beyond their "habitats". For example, climatologists have noticed interesting fact relationship between the frequency of hurricanes in the Atlantic and fair weather in Europe. As a rule, with an increase in the activity of tropical cyclogenesis, large sedentary cyclones form over Scandinavia. Along their periphery for the most part Western Europe southerly winds spread, which provide a stable warm weather. At the same time, Eastern Europe is in the grip of an anticyclone, which determines good weather. So our protracted "Indian summer" of 2005 is partly connected with the "raging" Atlantic.

There is no need to talk about the importance of studying tropical cyclones and predicting their evolution. Direct measurements in a cyclone are practically impossible, although many useful information was obtained during aircraft sounding and special expeditionary observations. Modern methods of research and forecast of tropical cyclones are based on numerical modeling and the use of satellite information, laboratory experiments. Methods have been developed for predicting the occurrence, evolution, and direction of movement of these cyclones based on numerical methods and satellite data. Although it is still impossible to accurately calculate the place of origin of a tropical cyclone, it is quite realistic to determine the most probable area of ​​its origin. Over the past 30 years, significant progress has been made in predicting the trajectories of cyclones.

The enormous damage caused by tropical cyclones poses the problem not only of predicting their development and movement, but also of possible influence on them in order to reduce their intensity and change the trajectory of movement. A wide variety of projects were proposed: scattering clouds with dry ice or silver iodide, cooling the ocean with icebergs, covering the water with a special oil film, irradiating the epicenter of a hurricane with microwaves from space or undermining it with hydrogen bombs. It should be noted that all of them are quite expensive and may turn out to be absolutely meaningless if not accurate forecast places of origin, size and intensity of the cyclone. In addition, it is impossible to calculate the consequences of such impacts, which can be no less devastating than the tropical cyclone itself. So for now, we can only hope to improve the methods of forecasting tropical cyclones and adequately respond to the warnings of specialists. And even now, thanks to the improvement of warning systems and methods of saving people, the number of human victims has begun to gradually decrease.

Text: Olga Razorenova (Senior Researcher, Institute of Oceanology RAS)
Photo: Levan Mtchedlishvili

In the tropical zone, at latitudes from 5 to 25° in both hemispheres, tropical cyclones are observed, which have tremendous destructive power. It has been calculated that if all the energy of only one tropical cyclone were turned into electrical energy, then it would be enough for all mankind for several years.

Tropical cyclones are small cyclones, averaging 100 to 200 miles in diameter, with very low pressure at the center (very deep cyclones).
They are accompanied by powerful, descending to the ground, thunderclouds, hurricane-force winds, heavy downpours, huge ocean waves. Even the largest modern ships find it very difficult to fight a hurricane, and often this struggle ends in the death of the ship.

The pressure in the central region of a tropical cyclone is on average 960 - 970 mbar, but sometimes 900 mbar or less. The difference in pressure between the center and periphery of tropical cyclones per 1° distance (111 km), the so-called baric gradient, is 30–40, and sometimes more than 100 mbar. while in ordinary cyclones it usually does not exceed 20 - 25 mbar.
For this reason, the wind speed in tropical cyclones usually reaches hurricane force up to 50 - 60 m/s and more. Tropical cyclones arise only over the oceans and seas. The reasons for their occurrence have not yet been fully elucidated. Currently, there are several theories of the formation of tropical cyclones.

According to one of them, cyclones arise from ascending currents of warm and humid air, which are accompanied by the release of huge amounts of latent thermal energy as a result of condensation of water vapor.
Another theory explains this phenomenon by the interaction of air masses of the northern and southern hemispheres in the zone of convergence of the trade winds. But one thing is absolutely clear that tropical cyclones arise in such oceanic areas and in those seasons of the year when the sea surface temperature is the highest and exceeds 26-27 °. The structure of tropical cyclones is still not entirely clear.
While hurricane winds, heavy showers and thunderstorms are raging around, in the center, with an average diameter of 10-15 miles, there is an area of ​​clear calm weather - the “eye of the storm”

The most dangerous is the right (in terms of movement) half of the cyclone in the northern hemisphere, and in the southern hemisphere - the left. Here, the wind speed often reaches 65 m / s and the speed of individual squally gusts is 100 m / s or more

Most often, tropical cyclones in the northern hemisphere are observed from August to September, and in the southern hemisphere in the Pacific Ocean from January to July, in the Indian Ocean from November to April. The exception is the northern part of the Indian Ocean, where tropical cyclones are more common from May to December

Tropical cyclones originating in the west of the Pacific Ocean are called typhoons, in the Atlantic Ocean - Antilles hurricanes, in the northern Indian Ocean - cyclones, and in the south - orkans, off the coast of Australia - "willy-willy". Unlike ordinary cyclones, tropical cyclones move with east to west, and some, crossing tropical latitudes, change direction and go in the northern hemisphere to the northeast, and in the southern hemisphere - to the southeast.
If, with the transition to middle latitudes, a tropical cyclone encounters a polar front, then it significantly increases in size and turns into an ordinary deep cyclone with a warm and cold front. On average per year in pacific ocean there are about 20 - 23 cyclones, in the Atlantic 12 - 13, in the Indian - about 15. The paths of tropical cyclones, with rare exceptions, are constant.
The speed of movement of tropical cyclones at first is small, but in well-developed ones it reaches 15-20 miles per hour or more. The duration of the existence of tropical cyclones is on average 8 - 10 days.

When a tropical cyclone passes into the sea, a characteristic, growing noise appears. Black or red wisps of broken clouds quickly sweep across the sky. A huge black cloud is approaching with great speed, covering the entire sky. The wind intensifies, becomes gusty, squalls begin to fly incessantly.
Thundering non-stop great strength thunder Huge blinding lightning often pierces the ensuing darkness. A very strong wind creates giant waves with great strength. Rainwater streams mix in the air with spray and foam from the waves, visibility is reduced to a few meters. This state of weather and sea can last for many hours.

When the center of a tropical cyclone (“eye of the storm”) passes, for 20-30 minutes the wind subsides to calm, clears up, you can see a blue or starry sky, but the sea does not decrease.
The waves here converge from all directions and create an extremely steep and chaotic crowd, very dangerous for ships ( standing waves about 40 m long). As you move away from the center of the cyclone, the excitement takes on a more ordered, regular character.

After passing through the "eye of the storm", the barometer makes a quick jump upwards, and a flurry of hurricane force again flies from the opposite rhumb.
General character weather becomes the same as before the passage of the center of the cyclone. Sometimes tornadoes are observed in a tropical cyclone - small eddies with a diameter of several hundred meters at a speed of up to 20 - 25 miles per hour. The wind in such a whirlwind has a colossal speed of 200 - 250 m/sec.
A distinctive feature of tornadoes is the funnel-shaped lowering of clouds with a long tail downward in the form of a trunk, the end of which sometimes touches the water. Tornadoes have tremendous destructive power.

The danger of tropical cyclones for navigation is further aggravated by the fact that, due to their relatively small size, they cannot always be detected on maps by weather forecasters.
For this reason, ships at sea cannot receive timely warnings about the origin and path of the hurricane. In this regard, especially importance have local signs and radio equipment to detect approaching tropical cyclones.
When information about tropical cyclones is transmitted by radio, they are given the female names Vera, Diana, Nancy, Charlotte, and others. In the old days, tropical cyclones were given the names of the ships that discovered them.

As already mentioned in the section “Waves on the sea”, the direction of the swell can be used to judge the position of the center of the cyclone, and the change in its direction-about direction cyclone movement. The appearance of a swell that does not come from the direction from which the wind is blowing or was blowing earlier is a sign of the approach of a tropical cyclone.

When a tropical cyclone approaches, atmospheric pressure changes dramatically, so observing barometer and barograph readings is one of important factors timely detection and prediction of an approaching tropical cyclone. Atmosphere pressure at a distance of 120 - 150 miles from the center of a tropical cyclone, it begins to gradually fall, but its daily course is still noticeably preserved.
Further, with the approach of the center of a tropical cyclone at a distance of 60 - 110 miles, the daily course of pressure is completely disturbed, the pressure drops sharply (pa 13 - 20 mbar per hour), the pressure drop stops only when the "eye of the storm" passes.
After passing through the center of a tropical cyclone, the pressure begins to rise rapidly at first, and then, with the removal of the center, more slowly, and finally reaches the normal value for the given region.

The approach of a tropical cyclone, sometimes at very large distances (up to 1500 miles). It is preceded by the appearance of cirrus filamentous clouds with curved ends, which are best observed at sunrise or sunset. If these clouds appear to converge at one point, then with a high probability we can assume that at a distance of about 500 miles from the ship, in the region of convergence of these clouds, the center of a tropical cyclone is located.
At a distance of about 300 miles from the center of a tropical cyclone, the direction of movement of cirrus clouds often coincides with the direction of movement of the cyclone. Cirrus clouds are not always an absolute sign of the approach of a tropical cyclone, but their appearance should not be ignored.
At a distance of 500 - 600 miles from the center of the cyclone, cirrocumulus clouds are usually observed, and at a distance of 200 - 250 miles, heaps of gloomy powerful cumulonimbus clouds, the view of the sky at this moment is menacing.
The appearance of cumulonimbus clouds is often preceded by the appearance on the horizon of a small, noticeably increasing and rapidly moving dark cloud - a "bull's eye".
At a distance of 200 to 250 miles from the center of a tropical cyclone, a good sign of its approach is the appearance of broken cumulus clouds.

Initially, these are single clouds, but as the center of the cyclone approaches, their number increases, they become denser and gradually turn into rain clouds.
At the same time, squalls with showers pass. The movement of broken-cumulus clouds indicates the direction of movement of the center of a tropical cyclone. If you face towards the movement of these clouds, then the center of the tropical cyclone will be located to the right of the vessel.

In 100 - 150 miles from the center of a tropical cyclone, heavy rain begins, which is clearly visible on the ship's radar screen.
Under normal radar observation, a band of heavy rain is detected at the limit of the radar range; this helps determine the vessel's position relative to the center of the tropical cyclone.
At 10 to 15 miles from the center the rain stops and the clouds disperse. After the passage of the central region of the tropical cyclone, the clouds again close and a shower of the same intensity begins as before the passage of the center of the cyclone, but the duration of the rain is somewhat shorter. With the removal of a tropical cyclone, rain clouds turn into cumulus and the rain stops.

When a tropical cyclone approaches, as well as when a normal cyclone approaches, halos and crowns around the sun and moon are sometimes observed.

The purple-red color of the dawn is a sign of the approach of a tropical cyclone. And the evening dawn is held for a long time and remains red until the end, without turning into yellow. At the same time, the shadow of the earth is clearly visible from the opposite side, the edge of which has an orange color.
Such a dawn can be observed 2 - 3 days before the onset of a cyclone. Sometimes tropical cyclones are preceded by sunrises and sunsets, at which the sky takes on a fiery or copper-red color with a variety of hues.

A day or more before the onset of a tropical cyclone, there is a clear sky, calm or light wind, a significant increase in temperature, absolute and relative humidity air (there is a strong stuffiness) and a violation of their daily course, from the beginning of the onset and further passage of the cyclone, a rapid drop in air temperature is observed.

At night, from the side of an approaching tropical cyclone, strong reflections of lightning (lightning) are often visible.

During radio reception, frequent discharges or a continuous crackle are heard, which intensifies as the cyclone approaches.

Separate bright spots appear on the radar screen, which are large droplets in the atmosphere

Wind direction in various parts of a tropical cyclone changes in the same way as in cyclones of temperate latitudes, differing only in a much faster transition from one rhumb to another. Wind direction is a good indication of the location of the center of a tropical cyclone.
By changing the direction of the wind, one can judge in which half of the cyclone relative to its path the ship is located (see "Ship avoidance of tropical and deep cyclones").

An increase in wind speed is a sign of the approach of a tropical cyclone, but this sign appears too late.