Eye of the tornado. The mystery of the “eye” of the hurricane, which scientists still cannot solve
Meteorologists distinguish several stages in the development of a tropical cyclone, with the change of which their danger increases. But such a division is conditional, of course, since in reality the process is continuous.
With wind speeds of up to seventeen meters per second, a cyclone is called a tropical depression, that is, an area of low atmospheric pressure. When the speed of air flows exceeds this limit, we are faced with a tropical storm. But the wind is getting stronger. And now the hurricane is already in full force. The wind, like an evil spirit unleashed from its chain, destroys everything in its path - its speed exceeds thirty meters per second. It’s good if it doesn’t reach densely populated areas, if it rampages only in the vastness of the ocean...
This is, in a very general form, the mechanism for the generation of huge tropical atmospheric vortices. While it is not yet fully understood, it remains one of the most difficult mysteries for weather science.
It has not yet been clarified, for example, to what extent and in what way cold air masses are involved here, invading the tropics from areas of temperate latitudes. And the fact that they are somehow involved in this process is beyond doubt among many researchers. It is known, for example, that typhoons in China and Japan are most often born during the change of East Asian monsoons (in spring and autumn), on the fronts of meetings of various air masses. It is quite reasonably believed that tropical cyclones arise in areas where differently heated air currents meet.
The hurricane is in no hurry
Born in the atmosphere of warm seas, a tropical cyclone immediately sets off on a long journey. We will follow him too. This is not difficult: its speed usually does not exceed twenty kilometers per hour. And upon reaching moderate latitudes, he even begins to make stops - as if to rest after a long journey.
Does this mean that a hurricane does not sweep through and does not strike, as they always write about it, as was just said in this book? Yes and no!
No, if we are talking about the movement of the atmospheric vortex itself; yes, if we are talking about the winds that blow in it. The circular movement of air inside a hurricane reaches enormous speeds and brings destruction with it. At the same time, this whole gigantic, furiously rotating atmospheric carousel is moving forward not so quickly - first to the west, and then, changing direction, to the east.
A fast ocean liner can easily escape an approaching cyclone. However, rather, not without difficulty. Sometimes it is not so easy to determine in which direction it is best to escape from the overtaking elements. Radio and air reconnaissance come to the aid of those at sea. It is especially dangerous to make a mistake when the ship finds itself near the place where the hurricane abruptly changes its original path.
It is not easy, very difficult, even for a large ship if it falls into the zone of a tropical hurricane. In the roar of raging waves, in the howl of a frantic wind, under an incessant downpour, suggesting the opening of the abyss of heaven, sailors, and especially passengers, get a complete picture of what a sea storm in the tropics is like.
In the open ocean during a cyclone, there are not those “correct” waves that usually gently splash at our feet when we stand on the shore of, for example, a lake. A hurricane wind furiously tears the surface of the sea, creating a chaotic crush of waves. A reddish light pours from the clouds, flying so low that it seems they are about to hit the foamy crest of a particularly high wave. And in this indescribable chaos, a water shaft fifteen to sixteen meters high can suddenly form. Each such shaft carries colossal energy; its impact is unsafe, as already mentioned, even for huge and durable ocean liners. That is why the profession of a sailor is still considered one of the most difficult, requiring from a person courage, enormous courage and the greatest dedication.
Sometimes such a riot of nature continues for up to two weeks. When a tropical cyclone moves over the warm ocean waters, it is provided with energy. The humid and superheated air sucked in by the giant natural pump only intensifies it. However, he does not stay in one place for long: without stopping his whirlwind, he finally finds himself in colder regions, where he loses his strength, weakens and collapses due to lack of energy.
"Eye" of the typhoon
In Japanese myths, one of the important places belongs to the god of storms. He is depicted as a terrible dragon rushing across the sky among darkness and angry waves. With his only eye, he looks out for prey below - something that can be destroyed.
In this fantastic image, surprisingly, there is something of reality. Tropical cyclones really have a kind of “eye” - still mysterious, not studied in detail, although sailors of past centuries knew about it.
This is its center, here the sky is clear, while all around the hurricane wind roars and whistles. But the ocean in this place is very dangerous. Here, in the center of the hurricane, huge waves rush from all sides. Several years ago, American scientists made an attempt to get into the “eye” of the storm to see for themselves what was happening there. The scientific expedition ended tragically, although the scientists were on the cruiser. Before the SOS signal went on air, observers transmitted from the ship: “The height of the waves reaches 40 meters.”
French pilot Pierre-André Molin witnessed the violence of Typhoon Vera in 1959. From then on, he decided to become a "typhoon hunter." Flying for scientific purposes in areas of tropical hurricanes, such hunters have already done a lot for science. Molan wrote an extremely interesting book about this.
Here are some excerpts from it:
“Dawn comes, revealing a fantastic sight: regular stripes of clouds stretch across our path, showing that we are heading straight into the “eye” of the typhoon.
The sea is raging, but a strange anomaly demonstrates all the evil cunning of nature manifested in a typhoon - the direction of a large swell does not depend on the direction of the wind, it can even go towards it: these waves are generated by a monstrous seething in the center of the typhoon, from where they diverge in concentric circles...
An exciting encounter with a typhoon. I've seen many pictures, but this time he's alive, and the sight becomes breathtaking. It even seems to me that I hear the roar of rotation of a gigantic mass with a radius of 300 kilometers; I must say that this illusion is facilitated by the continuous hum of our electronic “assistants”, merging with the roar of the engines.
Little by little, the whole figure emerges on the radar screen, the curved stripes become more and more frequent, as if they are compressed around the “eye” of the terrible Quasimodo, and then he himself emerges, a black hole on the screen, the “eye” of the storm...
Now we will no longer see the state of the sea until it appears before us in all its tragic grandeur. We are flying in a gray watery night, after which it seems that day will never come. Drops of water, or rather buckets, barrels of water, become invisible due to the speed with which they fly towards us, and yet completely obscure the wings from view. One may even doubt whether the laws of aerodynamics or Archimedes’ law support us, whether we fly or swim...
We continue to move deeper into the cyclone. There is some kind of interaction between him and the plane, an exchange of pushes, an intense struggle, which is accompanied not by screams, but by something like continuous singing...
Perhaps the plane does not break only because it does not have enough time to bend in one direction before it is bent in the other. Everyone is silent, everyone has enough to do without exchanging thoughts: they listen, they listen excitedly to how a set of airplane frames behaves. They literally listen to him like doctors.
I understand why those two people at the tail of the plane are needed, who watch the wings, checking whether the skin is giving way somewhere, whether the ailerons are in order, whether the engines are holding firmly, whether there is a fuel leak somewhere - a sure sign of internal failure , - and besides, whether a parachute probe, one of those that an airplane drops in a typhoon to take measurements, got into the propeller.
The man inside the "eye of the typhoon"
typhoon cyclone cloud atmosphere
Molan called the area of serene calm at the center of a tropical cyclone a “strange paradox.” In his book Typhoon Hunters, he gives a very impressive description of the interior of the "eye of a typhoon."
Molan gave this description after he flew through Typhoon Ruth on August 17, 1962 aboard the American flying superfortress Meteoboing 50 and witnessed the “eye of the typhoon” with his own eyes, being inside it at an altitude of three kilometers. Here are some excerpts from this description.
“...As we get closer to the eye, the strength of the shaking continuously increases. The plane vibrates. From sudden jerks you feel as if your heart and stomach are being torn out of place and that blood is gushing through all your internal organs. In this tiresome struggle, after each shock you are glad that the plane did not fall apart...
Suddenly the hum of our four engines emerges from the decorous silence. The plexiglass windows brighten as if on the brightest sunny day. This light looks incredible after a world from which the sun seemed to be banished forever... Our eyes are presented with the most majestic, most exciting phenomenon that nature has ever created. Everyone who has been in the eye of the typhoon returns from there with a feeling of admiration and horror, which there are not enough words to describe...
We fly at an altitude of 3000 m in a well 22 km in diameter, in which several cirrus clouds float, peaceful as toys. The walls of this well are made up of a storm - held by a mysterious order, a mysterious boundary, boiling clouds, engulfed in the most severe convulsions. As the plane rolls through turns, our eyes rise to the top of the wall, to the exit of this well fifteen thousand meters above us. And before our eyes unfold these boiling fifteen-kilometer walls, this gigantic abyss, this round hole, which made us call the whole phenomenon the eye of the typhoon.
Above this crater you can see the blue sky, reminiscent of joy and relaxation, and the life-giving sun, throwing its rays almost vertically into the abyss. Shining in their silent rage, the cascades of the storm around us are kept from falling by a monstrous immeasurable effort, the walls of the well tremble under the rays of the sun ... "
From the point of view of a physicist, there is, of course, no paradox in the phenomenon called the “eye of the typhoon”. Because this phenomenon is similar to the Moon circling around the Earth or the Earth around the Sun. There, certain cosmic bodies make their endless fall under the influence of gravity. And here huge masses of air fall into the depression zone. Of course, such a fall cannot be called endless - after all, it does not occur in airless space, and therefore is accompanied by intensive expenditure of energy. However, this peculiar fall continues for several days.
Of course, there is some specificity in the fall, which is expressed in the movement of air masses around the “eye of the typhoon.” This specificity was well expressed by Molan. He wrote: “Air masses rushing towards a zone of low pressure pass by, preventing external air masses from penetrating into it(our italics - Author) and creating a wide area of powerful rotational motion, on which the bulk of the energy is spent. The air masses move tangentially to the hole to be filled, so that they no longer so much fill it as interfere make this the only component of all forces that is directed towards the center of the area with reduced pressure... Centrifugal forces acting on moving masses of air prevent the filling of this area; each particle, like a stone in a sling, tends to move away, and as a result, these centrifugal forces, sucking out the air, lower the pressure even more.”
This is why meteorologists have to closely monitor the “eyes” of hurricanes. These strange phenomena provide invaluable information about how strong and destructive hurricanes will be and which regions will be hit the hardest. And yet, despite intense attention to both the hurricanes themselves and the mysteries of their “eyes,” researchers have difficulty understanding how they form. An article published in 2006 gave about a hundred explanations for how hurricane eyes form, but many of them clearly contradict each other, so the final conclusion on this issue is still to be determined.
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Difficulties in modeling the process of formation of the “eye” of a hurricane
The authors of the article write that it is very difficult to find out the nature of the formation of the “eye” and to model it, since the internal structure of hurricanes and other cyclones depends on several forces and phenomena, and at the same time they are all very complex and poorly understood. Scientists are still struggling to understand how these complex systems interact.
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Despite the fact that all the “eyes” of hurricanes are similar in appearance, scientists have not even been able to determine whether the same mechanisms are actually responsible for different classes of atmospheric vortices. Given the lack of this fundamental understanding, it is impossible to determine with certainty the rules for the formation of these "eyes."
Atmospheric cyclone model
Despite all the difficulties of the work, the researchers managed to create, in their words, the most complex model of an atmospheric cyclone, which they described in a paper published in the Journal of Fluid Mechanics in January 2017.
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In a 2018 paper, scientists wrote that modeling the “eye” of a cyclone requires special care. They also emphasized that when creating their model, such essential characteristics of atmospheric vortices as vertical stratification of air temperature, changing anisotropic viscosity of the vortex, as well as latent heat release due to condensation of water vapor were not taken into account.
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Nevertheless, scientists call their model a reasonable but simplified analogue of a tropical storm that can form in real conditions.
Under what conditions does the “eye” of a hurricane form?
Through their model, the researchers discovered that the eye of a hurricane cannot form without four boundary conditions being met. Here they are:
- The Ekman number (equal to the ratio of internal friction in a fluid to the Coriolis force caused by the planet's rotation) should not be too high.
- The Reynolds number, which measures the ratio of inertial (motion) forces to atmospheric viscosity, cannot be too low.
- The Rossby number cannot be too high.
- But it also shouldn’t be very low. The Rossby number measures the relationship between the force of a cyclone's motion and the Coriolis force.
![](https://i2.wp.com/homsk.com/upload/media/entries/2018-01/17/1321-13-abb2849a233822abeb77bced16280c43.jpg)
The important point here is that the eye of a cyclone is formed by the right balance of the storm's internal friction, its speed, and the force of the Earth's rotation that acts on the storm (at least in this simplified model created by scientists).
The researchers emphasize that their results do not fully answer the question of why “eyes” form in hurricanes, since too many factors were not taken into account in the model they created. In addition, there is a possibility that hurricanes in reality form very differently than in the simulations. Also, their model does not cover other forms of atmospheric cyclones, such as tornadoes.
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Prospects for new research
So is there any benefit from this research? It helps determine where to go next to study the formation of cyclone eyes by answering some basic questions about hurricanes, the scientists write. Namely: why do they form this way and not otherwise, and what will allow meteorologists to better predict the behavior of storms?
Every day we learn more and more sad news about how the powerful Hurricane Harvey, raging in the Gulf of Mexico, causes more and more destruction and claims an ever-increasing number of lives. Hurricanes, typhoons - all this is practically unknown to residents of the middle zone, and therefore we decided to tell you about what this natural disaster actually is.
What is a hurricane
The term "hurricane" has two main meanings. Firstly, a hurricane is a storm, that is, a very strong wind whose speed exceeds 30 m/s. Often such storms are accompanied by strong disturbances at sea or ocean. However, we are interested in the second, narrower and more familiar meaning, according to which a hurricane is a low-pressure weather system. It occurs over heated areas of open water of sufficient size and is accompanied by powerful thunderstorms, showers and storms. From space, a hurricane looks like a huge funnel of clouds: it receives energy from the fact that warm, moist air rises, after which the moisture condenses in the form of water vapor and falls as rain, while the warm air, which has become dry, falls down. Hurricanes are also called "warm-core cyclones" because the operating principle of polar and extratropical cyclones is completely different.
Storm winds during a typhoon cause the sea to crash huge waves onto the coastline
The word “hurricane” itself comes from the name of the Mayan god of the wind - Huracan. There is another popular name for a hurricane - “ tropical cyclone" But in Japan and the Far East hurricanes are called typhoons. They arise and maintain their strength only over the surface of large bodies of water, and if the wind blows a hurricane onto land, it will quickly exhaust itself. Therefore, it is the coastal areas that suffer the most from the elements, but heavy rains generated by hurricanes often cause extensive flooding even at a distance of 40 km from the coast. Despite the fact that tropical cyclones often cause enormous damage to infrastructure, they cannot be called absolute evil. Firstly, it is thanks to hurricanes that drought ends in some areas of the Earth and the vegetation landscape is restored. Secondly, tropical cyclones transfer large amounts of energy from equatorial latitudes towards temperate latitudes, which makes them an important component of global atmospheric circulation processes. This leads to a decrease in temperature on various parts of the planet's surface, so that it avoids overheating and maintains a stable temperate climate.
What does a hurricane consist of: the eye of the storm
Diagram of the structure of a hurricane: red arrows show flows of warm air, blue arrows show gradually cooling air
Eye of the Storm(or simply “eye”) is the central part of the cyclone, in which warm air falls down. As a rule, it retains a regular round shape, and its diameter can reach from 3 to 370 km, but on average the size of the eye is 30−60 km. An interesting “stadium effect” is associated with it: in large cyclones, the upper part of the eye is noticeably wider than the lower, which, when observed from the inside, actually resembles the shape of a stadium bleacher.
Large cyclones usually have a clear eye and a clear sky; in small ones it can be partially or completely covered with clouds, which is characterized by significant thunderstorm activity.
Wall of the eye
The eye wall of a storm can be seen either from inside the hurricane or in photographs of space satellites
In fact, the eye is an opening that forms a ring of dense cumulus thunderclouds. Here the clouds reach their greatest height, but the maximum wind speed is not achieved at the top of the wall, but at a low altitude above the surface of the water or land. Remember the videos from the Internet where strong winds lift small buildings off the ground and blow away cars? This is precisely the destructive power of a hurricane wall passing over a populated area.
Strong cyclones (category 3+) change the wall several times throughout their existence. At the same time, the old wall narrows to 10-25 km, and it is replaced by a new one of larger diameter. Changing the wall is a good sign: during each such procedure the cyclone weakens, but it is worth keeping in mind that after the final formation of the new wall it will quickly gain its previous strength.
Outer zone
The wide canvas of a hurricane consists of so-called rain bands - lines of dense thunderstorm clouds that slowly diverge from the center of the cyclone. The wall and outer zone is the area where moist air rises through circulation cells, but they are all smaller than the central one.
What happens when a hurricane makes landfall? An increase in surface friction causes a concentration of air flows and, as a result, rainfall.
However, the hurricane is not limited to these categories. Due to the centrifugal movement of air, it forms cloud cover even at very high altitudes. These clouds have little in common with the dense cumulus cover of the wall and outer zone: light and cirrus, they move quickly from the center of the cyclone and gradually disappear. They can become the first signal warning of the imminent arrival of a cyclone.
Hurricane Harvey
The aftermath of Hurricane Harvey: highways turned into pools of dirty water
So what makes it stand out among its peers? Harvey", currently turning Texas into a water-covered wasteland? For starters, this is the strongest hurricane in the Gulf of Mexico since the famous Katrina, which hit the United States in 2005. He was initially classified as category four on the Saffir-Simpson scale. This is the so-called huge hurricane": the wind speed on its territory reaches 50−70 m/s, and the flooded zone is located at an altitude of up to 3 meters above sea level, while the floods extend ten kilometers inland.
On the last day of summer, the US National Weather Service reported that Harvey had weakened and moved from a tropical storm to a tropical depression: wind speeds had dropped significantly, but heavy rainfall was still continuing. We can only hope that the cyclone will soon disappear altogether: at present, federal authorities are finding it difficult to give even an approximate estimate of the damage that the disaster caused along its entire path.