Tropical eddy tower

a tropical eddy tower is a frontless low pressure system with organized convection, heavy thunderstorms and a closed surface wind circulation around the low pressure center.

Tropical eddy towers rotate cyclonically, thus in the Northern Hemisphere against the clockwise direction, in the Southern Hemisphere in the clockwise direction. This rotation lends its typical, spiral arranged cloud volumes to the eddy tower. The development conditions are mostly fulfilled in the Tropics or Subtropen. Depending upon region of the emergence tropical eddy towers carry different auxiliary designations:

as hurricanes tropical eddy towers in the North Atlantic, east the date border and in the south Pacific are designated North Pacific east of 160° east, if they achieve a maximum central wind force of over 118 km/h.
a cyclone is a violent eddy tower in the gulf of Bengalen. Also the violent eddy towers within the range of Mauritius, La Réunion, Madagascar and the African east coast, occurring in the Indian ocean south the equator, are called Zyklone.
as Taifun tropical eddy towers in the northwest part of the Pacific ocean are designated.

The classification of a tropical eddy tower into different strengths is made by the Saffir Simpson scale.

Table of contents

development conditions

friction and air humidity
tropical eddy towers form itself only over water surfaces, since the friction is substantially lower here than ashore and because air is damp here enough, in order sufficiently convection to cause. The air humidity plays a substantial role, is there in it energy (latent warmth) contained. This warmth is slowly extracted from the ocean with evaporating and delivered with the condensation fast again. This condensation warmth propels a tropical eddy tower mainly.
Sea surface temperature
the surface temperature of the water must amount to 26,5°C up to a depth of 40m at least.
Depth of water
the water must be deep at least 60 m.

for developing place

most tropical eddy towers northern 25 develops because of the favorable water temperatures within a zone, between the southern and. Degree of latitude lies. There the Corioliskraft, which is strong diverting Kraft of the earth rotation, only starting from 5 degrees northern and southern latitude enough, in order to introduce a rotating motion of the Zyklone, is in principle impossible as developing zone for tropical eddy towers the equator area, which however it does not have to be called that these do not occur there.

Enstehungsgebiete und Zugbahnen von tropischen Wirbelstürmen.
Enstehungsgebiete and course courses of tropical eddy towers.

In these zones between 5. and 25. Additionally degree of latitude is supported developing a tropical eddy tower still by the internal-tropical Konvergenzzone (ITC). The ITC provides for ascending air masses and strong convection, because here near the surface the two trade winds collide (convergence). In approx. 12 - 15 km height strive air masses for ascending again apart (elevator divergence).

In the southAtlantic ocean and in the southeast Pacific there are very rarely tropical eddy towers, there here the cold Meeresströmungen Benguela - and Humboldtstrom the tropical oceans clearly cooling, so that the necessary water temperature of at least 26,5°C is reached rarely. To 26. March 2004 was observed the so far only tropical eddy tower in the south Atlantic before Brazil. In the autumn 2005 for the first time two tropical storms have those the coasts of Europe pre-aged Kanari islands and/or with Vince and delta. The Azores reaches. Sometimes on the Mediterranean storms are observed, which are similar to the tropical eddy towers.

7 developing areas result:

development stages

Schematischer Aufbau eines tropischen Wirbelsturms
schematic structure of a tropical eddy tower
if a wide, convection-releasing disturbance, for example a Easterly Wave or a non-tropical low over sufficiently warm water on sufficiently damp air masses and on favorable shearing conditions meets, can be released a receiving procedure.
the warmth freely becoming by condensing leads to the fact that ascending air is additionally accelerated. Thus a negative pressure develops, thus a low at the water surface. Air masses flowing from downside fulfill the same criteria and are likewise accelerated. Thus the chain process is not released however alone yet. Otherwise also in our areas from large thunderstorms tropical eddy towers would develop.
in addition comes now still that air masses inflowing from all sides on the convection area coined/shaped by low pressure (Low level Inflow) on the relatively frictionless water surface begin by the Corioliskraft, in order to circulate a rotation center around. A LLCC (Low level Circulation Centre) develops. This circulation organizes and supports convection now additionally. By the rotation can ascend now still more air. In addition by the rotation it is prevented that flowing air masses can adjust the negative pressure in the center. The rotation supports thereby the self-preservation of the low pressure in the rotation center. The faster the eddy tower turns, the more warm, damp air to condensing is brought. If air enough humidity did not deliver continues to ascend it and moves in the height sideways away from the rotation center (High level Outflow). This video with English explanation to the topic Low level Inflow and High level Outflow obtain a very good impression.
the developed system continues to itself intensify now ever, as long as the conditions permit it. The development conditions are optimally take place an intensification up to an upper limit. This cannot be exceeded, since the Oberflächenreibung and other reasons cause a braking effect. The Taifun tip ( northwest Pacific, 1979) with 870 Hektopascal core pressure and 2200 km diameters holds the record. Tropical eddy towers on the average reach a diameter of 500 - 700 km. Thus they are clearly smaller than non-tropical low pressure systems.
The eye of Taifun Odessa, Pacific ocean, August 1985
turns the tropical eddy tower fast enough, then even an eye can form. The eye down-sank a relatively clear, weak-windy range around the rotation center in that cold dry air from above. The eye of high-reaching rain clouds, the Eyewall is surrounded. The tropical eddy tower within the range of these Eyewall achieves the highest wind velocities. Since the storm exhibits still another additional independent movement, which is added still to the rotation speed in addition, the main wind field always is on the side, where the rotation and the independent movement point to the same direction. Example: A cyclone with a rotation speed of 200 km/h draws on the northern hemisphere against the clockwise direction turning with a true airspeed of 30 km/h arises northward in such a way a total speed to the eastern Eyewall of 230 km/h. On the western side however only 170 km/h one reaches, since the independent movement works here against the rotation.
tropical eddy towers move themselves differently fast: in low widths with 8 to 32 kilometers per hour, in higher widths with up to 80 kilometers per hour. On both earth hemispheres draw the Zyklone first usually in western direction and turn around then parabelförmig eastward. In the Northern Hemisphere usually as follows: W SIZE N NO. They leave the range of favorable conditions then sometime and weaken themselves, either by land contact (Landfall), to cold water, dry air masses or because of to high shearing. The tropical eddy tower John, who swept 1994 31 days long over the Pacific, holds the record at longevity. If tropical eddy towers reach the Frontalzone of the middle widths, they can be converted into a non-tropical low pressure system (Extratropical Transition).


tropical eddy towers rank among the natural catastrophes, since from them several dangers proceed, which threaten humans, nature and real values. A cyclone demanded most victims 1970 in Bangladesh, at that time died approximately 300,000 humans:

Close of the eye are possible for storm tide continual one high wind velocities, to over 250 km/h. Thus it can come accumulating tide of to over 10m NN. This can lead also already substantial built structures to extensive floodings, additionally is endangered at these speeds.
Böen are possible for wind over 350 km/h. At these speeds also substantial built structures are endangered.
within a daily can fall over 500 mm precipitation. These enormous rain quantities release ashore then frequently devastating landslides and inundations .
over 20 m high waves threaten the navigation as well as the coasts and islands.
Of Tornadoes
these small-scale air eddies are a frequent accompaniment of tropical eddy towers. They form in the thunderstorms, which circle the tropical eddy tower. In addition, usually it acts thereby around Wasserhosen, with the Landfall arises oneself Tornadoes over country.

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