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PRESENTATION IN ENGLISH TORNADO
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- 2. A tornado is a violently rotating column of air that is in contact with both the
- 3. There are several scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by
- 4. Etymology The word tornado is an altered form of the Spanish word tronada, which means "thunderstorm".
- 5. Definitions A tornado is "a violently rotating column of air, in contact with the ground, either
- 6. Funnel cloud A tornado is not necessarily visible; however, the intense low pressure caused by the
- 7. Size and shape Most tornadoes take on the appearance of a narrow funnel, a few hundred
- 8. In the United States, tornadoes are around 500 feet (150 m) across on average and travel
- 9. Appearance Tornadoes can have a wide range of colors, depending on the environment in which they
- 10. Rotation Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern hemisphere
- 11. Electromagnetic, lightning, and other effects Tornadoes emit on the electromagnetic spectrum, with sferics and E-field effects
- 12. Detection Rigorous attempts to warn of tornadoes began in the United States in the mid-20th century.
- 14. Скачать презентацию
A tornado is a violently rotating column of air that is in contact with both
A tornado is a violently rotating column of air that is in contact with both
Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout. Waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non-supercellular tornadoes that develop over bodies of water, but there is disagreement over whether to classify them as true tornadoes. These spiraling columns of air frequently develop in tropical areas close to the equator, and are less common at high latitudes. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, and steam devil; downbursts are frequently confused with tornadoes, though their action is dissimilar.
Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes occur in theTornado Alley region of the United States, although they can occur nearly anywhere in North America. They also occasionally occur in south-central and eastern Asia, northern and east-central South America, Southern Africa northwestern and southeast Europe, western and southeastern Australia, and New Zealand. Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes ordebris balls, as well as through the efforts of storm spotters.
There are several scales for rating the strength of tornadoes. The Fujita
There are several scales for rating the strength of tornadoes. The Fujita
Etymology
The word tornado is an altered form of the Spanish word tronada, which means
Etymology
The word tornado is an altered form of the Spanish word tronada, which means
Definitions
A tornado is "a violently rotating column of air, in contact
Definitions
A tornado is "a violently rotating column of air, in contact
Funnel cloud
A tornado is not necessarily visible; however, the intense low
Funnel cloud
A tornado is not necessarily visible; however, the intense low
There is some disagreement over the definition of funnel cloud and condensation funnel. According to the Glossary of Meteorology, a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition. Among many meteorologists, the funnel cloud term is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform cloud.
Tornadoes often begin as funnel clouds with no associated strong winds at the surface, and not all funnel clouds evolve into tornadoes. Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance.
Size and shape
Most tornadoes take on the appearance of a narrow funnel,
Size and shape
Most tornadoes take on the appearance of a narrow funnel,
Small, relatively weak landspouts may be visible only as a small swirl of dust on the ground. Although the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 40 mph (64 km/h), the circulation is considered a tornado. A tornado with a nearly cylindrical profile and relative low height is sometimes referred to as a "stovepipe" tornado. Large single-vortex tornadoes can look like large wedges stuck into the ground, and so are known as "wedge tornadoes" or "wedges". The "stovepipe" classification is also used for this type of tornado, if it otherwise fits that profile. A wedge can be so wide that it appears to be a block of dark clouds, wider than the distance from the cloud base to the ground. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance. Many, but not all major tornadoes are wedges. Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist into complex shapes. These tornadoes are said to be "roping out", or becoming a "rope tornado". When they rope out, the length of their funnel increases, which forces the winds within the funnel to weaken due to conservation of angular momentum. Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or they may be completely obscured by condensation, dust, and debris, appearing to be a single funnel.
In the United States, tornadoes are around 500 feet (150 m) across on
In the United States, tornadoes are around 500 feet (150 m) across on
In terms of path length, the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925, was on the ground continuously for 219 miles (352 km). Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are composed of a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in the case of the Tri-State Tornado. In fact, modern reanalysis of the path suggests that the tornado may have begun 15 miles (24 km) further west than previously thought.
Appearance
Tornadoes can have a wide range of colors, depending on the
Appearance
Tornadoes can have a wide range of colors, depending on the
Photographs of the Waurika, Oklahoma tornado of May 30, 1976, taken at nearly the same time by two photographers. In the top picture, the tornado is lit with the sunlight focused from behind the camera, thus the funnel appears bluish. In the lower image, where the camera is facing the opposite direction, the sun is behind the tornado, giving it a dark appearance.
Lighting conditions are a major factor in the appearance of a tornado. A tornado which is "back-lit" (viewed with the sun behind it) appears very dark. The same tornado, viewed with the sun at the observer's back, may appear gray or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink.
Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and the darkness of night are all factors which can reduce the visibility of tornadoes. Tornadoes occurring in these conditions are especially dangerous, since only weather radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm's path. Most significant tornadoes form under the storm's updraft base, which is rain-free, making them visible.Also, most tornadoes occur in the late afternoon, when the bright sun can penetrate even the thickest clouds.Night-time tornadoes are often illuminated by frequent lightning.
There is mounting evidence, including Doppler On Wheels mobile radar images and eyewitness accounts, that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye of tropical cyclones. This area would be clear (possibly full of dust), have relatively light winds, and be very dark, since the light would be blocked by swirling debris on the outside of the tornado. Lightning is said to be the source of illumination for those who claim to have seen the interior of a tornado.
Rotation
Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern
Rotation
Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern
Approximately 1 percent of tornadoes rotate in an anticyclonic direction in the northern hemisphere. Typically, systems as weak as landspouts and gustnadoes can rotate anticyclonically, and usually only those which form on the anticyclonic shear side of the descending rear flank downdraft in a cyclonic supercell. On rare occasions, anticyclonic tornadoes form in association with the mesoanticyclone of an anticyclonic supercell, in the same manner as the typical cyclonic tornado, or as a companion tornado either as a satellite tornado or associated with anticyclonic eddies within a supercell.
Electromagnetic, lightning, and other effects
Tornadoes emit on the electromagnetic spectrum, with sferics and E-field effects detected. There
Electromagnetic, lightning, and other effects
Tornadoes emit on the electromagnetic spectrum, with sferics and E-field effects detected. There
Luminosity has been reported in the past and is probably due to misidentification of external light sources such as lightning, city lights, and power flashes from broken lines, as internal sources are now uncommonly reported and are not known to ever have been recorded. In addition to winds, tornadoes also exhibit changes in atmospheric variables such astemperature, moisture, and pressure. For example, on June 24, 2003 near Manchester, South Dakota, a probe measured a 100 mbar (hPa) (2.95 inHg) pressure decrease. The pressure dropped gradually as the vortex approached then dropped extremely rapidly to 850 mbar (hPa) (25.10 inHg) in the core of the violent tornado before rising rapidly as the vortex moved away, resulting in a V-shape pressure trace. Temperature tends to decrease and moisture content to increase in the immediate vicinity of a tornado.
Detection
Rigorous attempts to warn of tornadoes began in the United States
Detection
Rigorous attempts to warn of tornadoes began in the United States