Archival article from No. 6 (42) 2005

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

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

Intense tropical cyclones in each region have their own name. In the Atlantic and northeast Pacific they are called hurricanes; in the north-west of the Pacific Ocean - typhoons; in the Arabian Sea and the Bay of Bengal - by cyclones; in the southern part of the Indian Ocean - by the Orcans; off the coast of Australia - willy-willy; in Oceania - willy-wow; in the Philippines - baguio.

Tropical cyclones are huge eddies that reach 1000-1500 km in diameter and extend throughout the entire troposphere. A distinctive feature of tropical cyclones is a significant drop in pressure at short distances, which leads to the formation of hurricane winds. The pressure in the center of developed cyclones is about 950-960 hPa (the minimum recorded is 855 hPa).

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

Most tropical cyclones are formed in the intertropical convergence zone - the zone of convergence of the trade winds of the two hemispheres, or trade winds, and the equatorial westerly 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 emergence and further intensification of a tropical cyclone? First of all, this is the presence of an initial disturbance and an insignificant horizontal wind shear between the lower and upper troposphere. To create the "twisting" effect, a sufficient value of the Coriolis force is required due to the Earth's rotation around its axis - tropical cyclones are not formed 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, it 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 much of the heat needed to keep the pressure low 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 a sharp decrease in pressure in the center of a tropical cyclone. A tropical cyclone can be thought of as a heat engine, the work of which is associated with the ocean as a source of energy and as a trigger - an initial vortex is formed over an overheated area 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 determined by various atmospheric processes. We are dealing with a complex complex of interactions between the ocean and the atmosphere.

A mature tropical cyclone is a powerful atmospheric vortex, which is characterized by large pressure gradients (drops) and, consequently, hurricane winds - up to 90 m / s, and the belt of maximum winds is located between 20 and 50 km from the center. In tropical cyclones, powerful clouds develop, 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 a calm, precipitation suddenly stops at its border. The eye is surrounded by a wall of powerful clouds. Satellite images revealed the existence of "hot towers" - high-altitude zones of rain clouds, which are located above the "walls" of this very "eye" much higher than the main part of the hurricane. The "towers" extend all the way to the "ceiling" - the upper layers of the troposphere. According to experts, "hot towers" play a key role in the process of increasing the power of the 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 devastating 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 produces an amount of energy equal to several thousand atomic bombs.

In three weeks, the hurricane generates energy comparable to that which our Bratsk hydroelectric power station would have produced in 26 thousand years. Humanity is not yet able to use this energy, or receive it in such quantities from any other sources.

The formed 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 bend around the subtropical anticyclone and its direction changes to the northeast. Such a point on the trajectory is called a pivot point. Cyclone trajectories are mostly curvilinear, sometimes even "loops" appear. The average speed of movement of tropical cyclones within the tropics is only 10-20 km / h. Going out on land or in middle latitudes, a tropical cyclone dies out or turns into an intense cyclone of temperate latitudes. In the summer-autumn period, the Russian Primorye is often exposed to such cyclones - former typhoons, bringing abnormal precipitation and hurricane winds. Thus, in 1973, a typhoon in 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 the Far East, flooding the Primorsky and Khabarovsk Territories.

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

Tropical cyclones that have become tropical hurricanes get their names. This tradition dates back to World War II, when meteorologists from the US Air and Navy monitored typhoons and, to avoid confusion, named typhoons after their wives or girlfriends. After the war, the US National Weather Service compiled an alphabetical list of female names to facilitate communication and avoid the hassle of developing multiple 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 Meteorological Service, included male names in the list. Justice has triumphed. (Not all evil comes from a woman!) These lists are used constantly and are pre-compiled for each year and each region. However, in the event that a tropical cyclone is particularly destructive, the name assigned to it is deleted from the list and replaced by another. So we can quite definitely say - we will never hear about a hurricane named "Katrina" again.

The devastating effect of tropical cyclones is caused by hurricane winds, 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 precipitation - 182 centimeters per day. The storm surge is added to the rainfall - the rise in ocean level, reaching 10 m in extreme cases. Floods associated with storm surges are the most destructive consequences of hurricanes. In 1970, cyclone Ada in the Indian Ocean flooded the low coast of Bangladesh with surges. Then more than 300 thousand people died. Hurricane Hugo in 1989 brought down a 6-meter-high wall of water across South Carolina. Such a blow is capable of destroying buildings, roads, and eroding banks.

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 west of the Pacific Ocean. According to the Hydrometeorological Center of Russia, where a database of tropical cyclones around the globe is collected, an average of 26 tropical cyclones are formed in the west of the Pacific Ocean. In the Atlantic, the peak of hurricanes occurs in August-September and there are about 9-10 cyclones per year. Research by scientists has shown that tropical cyclone activity has increased in the Atlantic in recent decades. So, from 1970 to 1979, their number was 81, from 1980 to 1989 - 96, from 1990 to 1999 - 105; and in 1995, 19 tropical cyclones were recorded (the record still remains for 1933, when 21 cyclones formed in the Atlantic). According to the forecasts of American scientists, this tendency will continue in the first decades of the 21st century, and already the current 2005 may break all records. This is due, first of all, to an increase in the temperature of the ocean surface. As shown by satellite data, in 2005 the water surface temperature in the Atlantic Basin increased, compared with previous years, by an average of 2-4 ° C.

Until recently, the record-breaking Atlantic cyclone 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, most likely, turned out to be the record holder in terms of its parameters: the minimum pressure in its center was 902 hPa, while the wind speed exceeded 75 m / s (gusts up to 90 m / s). Katrina originated on August 23, 2005 east of the Bahamas and, passing through the south of Florida and strengthening 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 US coast, marking the seventeenth tropical storm in the 2005 hurricane season.

Fortunately, she was weakened, not having time to cause colossal harm. Both Katrina and Rita originated north of normal latitudes, where Atlantic tropical cyclones swirl. But most unusual for the Atlantic was the twentieth hurricane named Vince. He managed to turn around in the Azores area, which is much to the north (30-35 parallel) of the usual area of ​​their formation. True, he failed to achieve great 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 an interesting fact about the relationship between the frequency of hurricanes in the Atlantic and good weather in Europe. As a rule, with an increase in the activity of tropical cyclogenesis, large inactive cyclones are formed over Scandinavia. On their periphery, southerly winds spread to most of Western Europe, which provide stable warm weather. At the same time, Eastern Europe is at the mercy of an anticyclone, which causes good weather. So our protracted "Indian summer" 2005 is partly due to 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 a lot of useful information was obtained during airborne sounding and special expeditionary observations. Modern methods of research and forecasting of tropical cyclones are based on numerical modeling and the use of satellite information, laboratory experiments. Methods have been developed to predict the occurrence, evolution and direction of movement of these cyclones based on numerical methods and satellite data. Although it is not yet possible to accurately calculate the place of origin of a tropical cyclone, it is quite possible 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 task of not only predicting their development and movement, but also the possible impact on them in order to reduce their intensity and change the trajectory of movement. A variety of projects were proposed: dispersing clouds with dry ice or silver iodide, cooling the ocean with icebergs, covering water with a special oil film, irradiating the epicenter of a hurricane with microwaves from space or detonating it with hydrogen bombs. It should be noted that all of them are quite expensive and may turn out to be absolutely meaningless if there is no accurate prediction of the origin, size and intensity of the cyclone. In addition, it is impossible to calculate the consequences of such impacts, which may be no less destructive than the tropical cyclone itself. So for now, we can only hope to improve methods for forecasting tropical cyclones and to adequately respond to warnings from specialists. And even now, thanks to the improvement of warning systems and methods of rescuing people, the number of human victims has begun to gradually decline.

Text: Olga Razorenova (Senior Researcher, Institute of Oceanology, Russian Academy of Sciences)
Photo: Levan Mtchedlishvili

Tropical cyclones

Tropical cyclones carry enormous reserves of energy and are highly destructive. Kinetic energy of 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 of the 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 rainfall, as well as storm surges (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 have experienced the worst floods in the past 200 years. The total economic damage from the hurricane exceeded $ 5 billion.

Areas of origin of tropical cyclones

Tropical cyclones can occur at any time of the year in the tropical parts of all oceans, with the exception of the Southeast Pacific and South 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 of occurrence 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 ° N and south of 22 ° S has never been observed. Tropical cyclones, which have reached significant intensity, have their own name in each region. In the eastern part of the Pacific Ocean and in the Atlantic they are called hurricanes (from the Spanish word "huracan" or the English "harikane"), in the countries of the Indian subcontinent - 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-wah" in Oceania and "baguio" in the Philippines.

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

Causes and evolution of tropical cyclones

Tropical cyclones form where there is a high water surface temperature(above 26 °), and the water-air temperature difference is more than 2 °. This leads to increased evaporation, an increase in moisture reserves 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 humidified above the water surface. The rotation of the Earth gives a vortex motion to the rise of air, and the vortex becomes like a giant top, the energy of which is immense.

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 a calm period. 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 diameter of the eye of a storm in well-developed cyclones is 10 - 25 km, and in destructive ones it is 60 - 70 km.

Tropical cyclones, depending on their intensity, are called:

1. Tropical disturbance - low wind speeds (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.

There are four stages in the life cycle of a tropical cyclone.

1. Stage of formation. It starts with the appearance of the first closed isobar (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 are further developed.

2. Stage of young cyclone or stage of development. The cyclone begins to deepen rapidly, i.e. there is an intense 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 ​​stormy winds and intense rainfall is increasing in size. The diameter of tropical cyclones in the developmental and mature stages can range from 60 - 70 km to 1000 km.

4. Stage of decay. The beginning of the filling of the cyclone with an increase in pressure in its center). Attenuation occurs when a tropical cyclone moves to a zone of lower water surface temperatures or when moving to land. This is due to a decrease in the inflow of energy (heat and moisture) from the ocean surface, and when entering land, also with an increase in friction against the underlying surface.

After reaching 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, while remaining in the tropics, go to the mainland. Here they fill up quickly, but at the same time they manage to produce a lot of destruction.

Typhoons

Typhoons are among the most powerful and destructive tropical cyclones. The annual losses from typhoons cause significant damage to the economies of several Asian countries. Most economically underdeveloped countries struggle to repair the damage caused by typhoons.

Of the 25-30 typhoons that every year appear over the western part of the Pacific Ocean, they reach the Sea of ​​Japan and the Primorsky Territory in different years from 1 to 4. They all arise 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 reach 400 mm, and the wind speed is 20 - 35 m / s.

What is a cyclone? Almost everyone is interested in the weather - they look at forecasts, reports. At the same time, he often hears about cyclones and anticyclones. Most people know that these atmospheric phenomena are directly related to the weather outside the window. In this article we will try to figure out what they are.

A cyclone is a low-pressure zone surrounded by a circular wind system. Simply put, it is a massive flat atmospheric vortex. Moreover, the air in it moves in a spiral around the epicenter, gradually approaching it. The reason for this phenomenon is considered to be low pressure in the central part. Therefore, warm humid ones rush upward, revolving around the center of the cyclone (eyes). This causes the accumulation of high density clouds. In this zone, strong winds are raging, the speed of which can reach 270 km / h. The air is rotated counterclockwise with some swirl towards the center. In anticyclones, on the contrary, the air swirls clockwise. A tropical cyclone in the Southern Hemisphere works in much the same way. However, the directions are reversed. Cyclones can be of different sizes. Their diameter can be very large - up to several thousand kilometers. For example, a large cyclone can cover the entire European continent. Typically, these atmospheric phenomena are formed at specific geographic locations. For example, the southern cyclone comes to Europe from the Balkans; areas of the Mediterranean, Black and Caspian Seas.

Cyclone formation mechanism - first phase

What is a cyclone and how is it formed? At the fronts, that is, in the zones of contact between warm and cold air masses, cyclones arise and develop. This natural phenomenon is formed when a mass of cold polar air meets a mass of warm, moist air. At the same time, the warm ones burst into the array of cold ones, forming in them something like a tongue. This is the beginning of the origin of the cyclone. Sliding relative to each other, these streams with different temperatures create a wave on the frontal surface, and, consequently, on the frontline itself. It turns out a formation resembling an arc, concave facing towards warm air masses. Its segment, located in the forward eastern part of the cyclone, is a warm front. The western part, which is located at the rear of the atmospheric phenomenon, is a cold front. In the interval between them, zones of good weather are often found in the cyclone, which usually lasts only a few hours. This deflection of the front line is accompanied by a decrease in pressure at the wave top.

Cyclone evolution: second phase

The atmospheric cyclone continues to evolve further. The formed wave, moving, as a rule, to the east, northeast or southeast, gradually deforms. The tongue of warm air penetrates further north, forming a well-defined warm sector of the cyclone. In its front part, warm air masses float on to colder and denser ones. During the rise, vapor condensation and the formation of powerful cumulus rain clouds, which leads to precipitation (rain or snow), which lasts for a long time. The width of the zone of such frontal precipitation is about 300 km in summer and 400 km in winter. At a distance of several hundred kilometers ahead of the warm front near the earth's surface, the air reaches an altitude of 10 km or more, at which moisture condensation occurs with the formation of ice crystals. White ones are formed from them. Therefore, it is from them that one can predict the approach of a warm cyclone front.

The third phase of the formation of the atmospheric phenomenon

Further characteristics of the cyclone. The humid warm air of the warm sector, passing over the colder surface of the Earth, forms low stratus clouds, fogs, drizzle. After passing the warm front, warm cloudy weather with southerly winds sets in. Signs of this are often the appearance of haze and light fog. Then a cold front approaches. Cold air, passing along it, floats under the warm and displaces it upward. This leads to the formation of cumulonimbus clouds. They cause showers, thunderstorms, accompanied by strong winds. The width of the cold front precipitation zone is about 70 km. Over time, the rear part of the cyclone comes to replace. It brings strong winds, cumulus clouds and cool weather. Over time, cold air pushes warm air to the east. After that, clear weather sets in.

How cyclones are formed: the fourth phase

As the tongue of warm air penetrates into the mass of cool air, it turns out to be more and more surrounded by cold air masses, and itself is displaced upward. This creates a zone of reduced pressure in the center of the cyclone, where the surrounding air masses rush. In the Northern Hemisphere, under the influence of the Earth's rotation, they turn counterclockwise. As mentioned above, southern cyclones have opposite directions of rotation of air masses. It is due to the fact that the Earth turns around its axis that the winds are directed not towards the center of the atmospheric phenomenon, but go tangentially to the circle around it. In the process of cyclone development, they intensify.

The fifth phase of cyclone evolution

Cool air in the atmospheric phenomenon moves at a higher speed than warm air. Therefore, the cold front of the cyclone gradually merges with the warm one, forming the so-called occlusion front. There is no longer a warm zone at the surface of the Earth. Only cold air masses remain there.

Warm air rises up, where it gradually cools and frees from moisture reserves, which fall to the ground in the form of rain or snow. The difference between the temperature of cold and warm air is gradually leveled. In this case, the cyclone begins to fade away. However, there is no complete homogeneity in these air masses. Following this cyclone, a second one appears near the front on the crest of a new wave. These atmospheric phenomena always occur in series, each one slightly south of the previous one. The height of the cyclone vortex often reaches the stratosphere, that is, it rises to a height of 9-12 km. Especially large ones can be found at altitudes of 20-25 km.

Cyclone speed

Cyclones are almost always in motion. The speed of their movement can be very different. However, it decreases with aging of the atmospheric phenomenon. Most often, they move at a speed of about 30-40 km / h, passing a distance of 1000-1500 km or more in 24 hours. Sometimes they move at a speed of 70-80 km per hour and even more, passing 1800-2000 km per day. At this rate, the cyclone, which today raged in the region of England, in 24 hours may already be in the region of Leningrad or Belarus, provoking a sharp change in the weather. As the center of the atmospheric phenomenon approaches, the pressure drops. There are various names for cyclones and hurricanes. One of the most famous is the Katrina, which caused serious damage to the United States.

Atmospheric fronts

We have already figured out what cyclones are. Next, we will talk about their structural components - atmospheric fronts. What makes the huge masses of humid air in the cyclone rise high up? To get an answer to this question, we first need to understand what the so-called atmospheric fronts are. We have already said that warm tropical air moves from the equator to the poles and on its way meets cold air masses of temperate latitudes. Since the properties of warm and cool air differ sharply, it is natural that their arrays cannot immediately mix. At the meeting point of air masses of different temperatures, a clearly defined strip arises - a transition zone between air fronts with different physical properties, which in meteorology is called the frontal surface. The zone dividing the air masses of temperate and tropical latitudes is called the polar front. And the frontal surface between the temperate and arctic latitudes is called arctic. Since the density of warm air masses is less than that of cold air masses, the front is an inclined plane, which always tilts towards the cold massif at an extremely small angle to the surface. Cool air, as thicker, when meeting with warm, raises the latter up. When imagining a front between air masses, it must always be borne in mind that this is an imaginary surface tilted above the ground. The line that forms when this surface crosses the earth is marked on weather maps.

Typhoon

I wonder if there is anything more beautiful in nature than such a phenomenon as a typhoon? A clear, calm sky above a well of two Everest-high walls created by an insane whirlwind, riddled with zigzags of lightning? However, big trouble threatens anyone who ends up at the bottom of this well ...

Originating in equatorial latitudes, typhoons head west, and then (in the Northern Hemisphere) turn northwest, north, or northeast. While each of them does not follow the exact path of the other, most of them follow a curve that is shaped like a parabola. The speed of typhoons increases as they move northward. If near the equator and in the direction to the west they move at a speed of only 17-20 km / h, then after turning to the northeast, their speed can reach 100 km / h. However, there are times when, unexpectedly deceiving all forecasts and calculations, typhoons either completely stop or rush madly forward.

Hurricane eye

The eye is a bowl with convex walls of clouds, in which there is a relatively weak wind or complete calm. The sky is clear or partially covered with clouds. The pressure is 0.9 times normal. The eye of a typhoon can be 5 to 200 km in diameter, depending on its stage of development. In a young hurricane, the size of the eye is 35-55 km, while in a developed hurricane it decreases to 18-30 km. During the decay stage of the typhoon, the eye grows again. The clearer it is, the more powerful the typhoon. In such hurricanes, the winds are stronger near the center. Closing all currents around the eye, the winds whirl at a speed of up to 425 km / h, gradually slowing down as they move away from the center.

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 air currents arise and the release of the stored solar heat and the condensation of the vapors contained in it. 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 also spreads in breadth, capturing more and more new areas on the surface of the ocean.

When you pour water out of the tub through the drain hole, a vortex will form. Roughly the same thing happens with the air rising upward at the origin of the cyclone - it begins to rotate.

The giant air pump continues to run, more moisture condenses on its funnel-shaped top, more heat being released. (American meteorologists calculated: 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 medium-strength cyclone releases approximately the same amount of energy as the 500,000 atomic bombs dropped over Hiroshima. The atmospheric pressure in the center of the incipient 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 cause of strong winds, which soon develop into hurricane ones. In an area 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 terrain 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 heights from 2 to 20 km.

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

Normal 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 upward, generating strong clouds.

If in the center:

A conventional cyclone air pressure compared to atmospheric (760 mm Hg) is 713-720 mm Hg;

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

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

Every year at least 70 tropical cyclones appear and fully develop on the globe.

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 there was 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. The sea wave reached a height of 10 m. About 400,000 people died.

Today there are modern methods for forecasting tropical cyclones (typhoons, hurricanes). Each suspicious cloud accumulation, where it did not arise, is photographed by meteorological satellites from space, the meteorological service planes fly to the "eye of the typhoon" to obtain accurate data. This information is put into computers to calculate the path and duration of a tropical cyclone (typhoon, hurricane) and alert the population in advance about the danger.

Hurricane

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

The main characteristics of hurricanes are:

Wind speed;

Movement paths;

Dimensions and construction;

Average duration of actions.

The most important characteristic of hurricanes is wind speed. From the table below (on the Beaufort scale) you can see 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 in size. Usually, its width is taken as the width of the zone of catastrophic destruction, which can be measured in hundreds of kilometers. The front of the hurricane reaches a length of up to 500 km. Hurricanes occur at any time of the year, but more frequently 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.

The hurricane is almost always clearly visible; when it approaches, a strong buzz is heard.

Hurricanes are one of the most powerful forces of the element. In terms of their harmful effects, they are not inferior to such terrible natural disasters as earthquakes. This is because they carry tremendous energy. Its amount released by an average hurricane in one hour is equal to the energy of a nuclear explosion of 36 megatons.

A hurricane poses a triple threat to people who get in its way. The most destructive are wind, waves and rain.

Often storms accompanied by a hurricane are much more dangerous than the hurricane wind 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 heavy rains, 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 the same number died from the consequences of a fierce epidemic.

A hurricane, when spreading over the sea, causes huge waves 10-12 meters high and more, damages or even leads to the death of a vessel.

The greatest danger during a hurricane is represented by objects lifted from the ground and spun up to high speed. Unlike storms, hurricanes travel in a narrow swath so they can be avoided. It is only necessary to determine the direction of its movement and move in the opposite direction.

The hurricane wind destroys strong and light buildings, devastates sown fields, breaks wires and knocks down power transmission and communication lines, damages transport highways and bridges, breaks and uproots trees, damages and sinks ships, causes accidents on public energy networks in production ... There were cases when a hurricane wind destroyed dams and dams, which led to large floods, threw trains off the rails, tore off bridges from supports, fell factory pipes, threw ships on land.

Tropical cyclones, hurricanes, typhoons

A particularly dangerous natural phenomenon is deep cyclones of various origins, which are associated with strong winds, heavy precipitation, surges and high wind waves in the sea. The depth of the cyclone is determined by the value of the air pressure at its center.

The size and power of deep cyclones depends on many factors and, first of all, on the place of their origin. The cyclones that originated in the tropical zone of latitudes are distinguished by the greatest power. They are called tropical in contrast to extratropical cyclones, among which are the cyclones of temperate latitudes and arctic cyclones. The higher the geographic latitude of the cyclone origin, the lower its maximum power.

Tropical cyclones carry enormous reserves of energy and are highly destructive. The kinetic energy of an average-sized tropical cyclone is comparable to the explosion energy of several powerful hydrogen bombs and accounts for about 10% of the total kinetic energy of the northern hemisphere.

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 tropical cyclones north of 35 ° N has never been noted. NS. and south of 22 ° S. NS.

Tropical cyclones can occur at any time of the year in the tropical parts of all oceans, with the exception of the Southeast Pacific and South 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.

Tropical cyclones usually originate over the oceans, and then move over their waters and reach the coasts of continents and islands, bringing down strong winds, rain streams on them, causing a surge wave up to 8 m high, as well as waves in the open sea, over 10 m high.

Tropical cyclones, which have reached significant intensity, have their own name in each region. In the eastern part of the Pacific Ocean and in the Atlantic they are called hurricanes (from the Spanish word "huracan" or the English "harikane"), in the countries of the Indian subcontinent - 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.

To describe the intensity of tropical cyclones, the Saffir-Simpson scale is used, shown in Table. 3.3.1.1. It can be seen from it that as the cyclone deepens, the wind speed and surge wave height increase in it, and the cyclone itself is classified either as a storm or as a hurricane from the first to the fifth category.

This scale is used by almost all hurricane and typhoon observing centers. Recently, the Saffir-Simpson scale has begun to be used to classify deep extratropical cyclones that have reached the strength of a storm or hurricane. From this table, it follows that hurricanes and typhoons have five categories (from a hurricane or typhoon of the first category H1 to a hurricane or typhoon of the fifth category H5). Tropical depressions and tropical storms are not categorized.

Table 3.3.1.1. Tropical cyclone scale

Type of	Category	Pressure, mb	Wind, km / h	Surge height, m	Tropical depression	TD		<63		Tropical storm	TS		63-117		Hurricane	H1	>980	119-152	1,3-1,7	Hurricane	H2	965-980	154-176	2,0-2,6	Hurricane	NZ	945-965	178-209	3,0-4,0	Hurricane	H4	920-945	211-250	4,3-6,0	Hurricane	H5	<920	>250	>6

There are four stages in the life cycle of a tropical cyclone:

1. Stage of formation. It begins with the appearance of the first closed isobar. The pressure in the center of the cyclone drops to 990 mb. Only about 10% of tropical depressions are further developed.

2. The stage of a young cyclone, or stage of development. The cyclone begins to deepen rapidly, i.e. there is an intense 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 ​​stormy winds and intense rainfall is increasing in size. The diameter of tropical cyclones in the developmental and mature stages can range from 60-70 to 1000 km.

4. Stage of decay. The beginning of filling the cyclone (pressure growth in its center). Attenuation occurs when a tropical cyclone moves to a zone of lower water surface temperatures or when moving to land. This is due to a decrease in the inflow of energy (heat and moisture) from the ocean surface, and when entering land, also with an increase in friction against the underlying surface.

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

For a long time, there has been a practice of assigning proper names to destructive hurricanes and typhoons. At different times, the principles of naming have changed. For hundreds of years, hurricanes in the Caribbean have been named according to the church calendar, on the day of which a devastating hurricane struck a major settlement.

Under these names, hurricanes entered the annals and legends. An example is Hurricane Santa Anna, which hit Puerto Rico on July 26, 1825 with exceptional force. At the end of the XIX century. Australian meteorologist Clement Regg began to call tropical storms by female names. Since 1953, the US National Hurricane Center has been publishing tentative lists of Atlantic tropical storms.

Until 1979, only female names were used in it. Since 1979, both female and male names have been used. The practice of compiling tentative lists of hurricanes and typhoons has spread to all regions. There are now 11 such regions in the oceans. These preliminary lists for all regions are created and updated by a special international committee of the World Meteorological Organization (WMO).

The damaging factors of hurricanes and typhoons:

Kinetic wind energy;

Heavy rainfall;

Surge wave;

Storm waves of considerable height.

Associated SNPs: strong wind, strong waves, intense rains, heavy hail, floods, floods, landslides, landslides, erosion and recycling of banks.

Hurricanes cause colossal damage to the coasts of North and South America, islands in the path of their spread. They strike these coasts with a frequency of once every few years, sometimes forming series within one year. One of the most devastating hurricanes - Mitch in October 1998 killed 10,000 people in Honduras and Nicaragua and left 2 million people homeless.

The hurricane caused the worst flooding in these countries over the past two hundred years. The total economic damage from the hurricane exceeded $ 5 billion. The greatest economic damage in the world was caused by Hurricane Andrew, which swept over the United States from August 23 to 27, 1992. Insurers paid out $ 17 billion, which covered about 57% of the losses from the hurricane.

The underdeveloped countries of the Caribbean have suffered severe damage from hurricanes, the consequences of which they have recovered for years. Hurricanes in mid-latitudes are rare: once every 8-10 years. In January 1923, the hurricane captured the entire European part of the USSR, and the center of the hurricane passed through Vologda. In September 1942, a hurricane swept over the central regions of the European part of our country.

The pressure difference was very large, and therefore hurricane speed winds were formed in places. The usual speed of cyclones is 30-40 km / h; but there are speeds over 80 km / h. The September cyclone of 1942 covered 2,400 km in one day (i.e., its speed was 100 km / h). On November 18, 2004, the hurricane hit Germany, then moved to Poland and Kaliningrad.

In Germany, the wind speed reached 160 km / h, in Poland 130 - km / h, in Kaliningrad - 120 km / h. In these countries, 11 people died, 7 of them in Poland. Everywhere the hurricane caused floods, breaks of power lines, damage to roofs of houses, upturned trees.

The annual losses from typhoons cause significant damage to the economies of several Asian countries. Most economically underdeveloped countries struggle to repair the damage caused by typhoons. Of the 25-30 typhoons that every year appear over the western part of the Pacific Ocean, the Sea of ​​Japan and the Primorsky Territory, i.e. on the territory of Russia, in different years from one to four typhoons come out, bringing a sharp deterioration in the weather and causing significant economic damage.

They all arise over the ocean northeast of the Philippines. The average duration of a typhoon is 11 days, and the maximum is 18 days. The 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.

The maximum daily precipitation amounts to 400 mm, and the wind speed is 20-35 m / s. In 2000, four typhoons entered the territory of Primorye, one of which - BOLAVEN - turned out to be the most destructive: 116 settlements were flooded, 196 bridges and about 2000 km of highways were damaged. A total of 32,000 people were injured and one person died. The economic damage amounted to more than 800 million rubles.

Forecasting hurricanes and typhoons, detecting their origin, tracking their trajectories is the most important task of meteorological services in many countries, primarily the USA, Japan, China, and Russia. To solve these problems, space monitoring methods, modeling of atmospheric processes, and synoptic forecasts are used.

To reduce damage from hurricanes and typhoons, primarily in terms of human casualties, methods of warning, evacuation, adaptation of industrial processes, engineering protection of banks, buildings and structures are used.