The Great Kuttalian: November 2017

Tornado

Weather and climate affects human life in many ways. That is why the American Geography Professor Ellsworth Huntington said, ‘Our life can develop only in the manner it is decided by the Sun, the Air and the Water. The logo of the India Meteorological Department also express the same. It has the following words in the logo ‘Adityaat jaayate vruShTi:’

The weather events that affect the life and property of mankind can be divided in to several groups on the basis of space and time. These scales of Meteorological events are:

Planetary waves scale systems – These are very large scale events affecting a large area of the globe almost through out the year. Examples: General Air circulation, ocean currents etc
Synoptic Scale events – These are large scale weather events that can affect an area of about 1000 to 600 kms and for a period of several weeks to several months. Indian summer monsoon is the best example for this type of weather event.
Macro scale events – These are medium scale weather events that can affect an area of 100 to 1000 kms and for a period of several days to several weeks. The monsoon depressions and the tropical cyclones that for in the Indian seas can be cited as examples of this kind of events.
Meso scale events – These are small scale weather events extending from 10 kms to 100 kms and can exist for a few hours. The Andhis, Kalabhaishaakis, the winter time fog are some examples.
Micro scale events – These are very very small events. They affect a very small area and for a very small period of time. Tornodoes and hailstorms can be cited as examples for this type of events.

Some weather phenomenon, what ever be its scale can create havac in the society. Tornodo is one such event. Though it is a micro scale event, it can affect greatly in the areas of its occurrence. It will be a very bad experience to the people who have experienced it.

Names of Tornodo (Etymology)

The word tornado is an altered form of the Spanish word tronada, which means "thunderstorm". This in turn was taken from the Latin tonare, meaning "to thunder". It most likely reached its present form through a combination of the Spanish tronada and tornar ("to turn"); however, this may be a folk etymology. A tornado is also commonly referred to as a "twister", and is also sometimes referred to by the old-fashioned colloquial term cyclone. The term "cyclone" is used as a synonym for "tornado" in the often-aired 1939 film The Wizard of Oz. The term "twister" is also used in that film, along with being the title of the 1996 tornado-related film Twister. In Hindi it is called as ‘Bavander’ and in North East India it is called as ‘Hathisnoora’ meaning the ‘trunk of an elephant”.

Formation

A tornado is a violently rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes. But they are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 177 kilometer per hour. They have a diameter of about 76 meter. They travel several kilometers before dissipating. The most extreme tornadoes (often seen in America) can attain wind speeds of more than 483 kilommeter per hour.

It all starts from a dark thunder cloud known as Cumulonimbus (Cb) cloud. A funnel shaped portion extends from the base of the Cumulonimbus cloud downwards. It does not extend vertically downwards, but like an elephant’s tusk it swings up and down while comming downwards. Before the funnel touch the ground we can observe the whirl near the ground. Dust, leaves and paper bits from the ground will go up with whirl. The funnel cloud will touch the ground with a roar. Once touches the ground then unimaginable events will happen. Roofs, human beings, animals, light vehicles like cars, heavy vehicles like buses and lorries will be lifted from the ground and thrown away. The description of the eye witnesses is only the mode of understanding the disasters due to a tornodo.

Places of occurrence

Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes occur in the Tornado 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 or debris balls, as well as through the efforts of storm spotters.

The research on tornodoes in India is very less. H.N. Gupta and S.K. Gosh of India Meteorological Department in 1978 have listed 35 tornodoes that have occured during 1876 to 1978. Among them 26 tornodoes have occurred during March, April and May months. They have mostly occurred in north east India. But they have also mentioned about a tornodo occurred in Kerala and another that have occurred in Tamil Nadu. In 1967 S.R. Saha of IMD have listed tornodoes that have occurred during 1838 to 1950.

Definition and Description(shape)

As mentioned earlier tornodo is a micro-scale phenomenon. It has diameter of 150 to 600 meters. The speed of its movement is roughly 30 to 45 kilometers per hour. It can travel to a distance of about 20 kilometers after touchdown. As per the records the distance of travel can be 500 meters to 500 kilometers. While moving the damaes due to the tornodo is due to its wind component. This wind can be from 70 to 200 kilometers per hour. Tornodoes are classified by two different methods on the basis of the wind speed associated with the tornodo. They are (1) Fujita-Pearson Scale (2) TORRO Scale.

The Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similarTORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine intensity and assign a rating.

Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout. Some 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. Cumulonimbus clouds often exhibits downbursts. But these downbursts are frequently confused with tornadoes, though their action is dissimilar.

The origin of a tornodo is from the circulation around an axis inside a thunder cloud or cumulonimbus cloud. Such a circulation inside these type of clouds happen because of the turbulance (updarfts and downdrafts) inside the cloud. But once a circulation inside a cumulonimbus cloud starts then it will increase the turbulance also. The wind raising upward raises as an anticyclonic whirl which creates a low pressure area inside the cloud. This low pressure will increase the speed of the whirl wind. This continues as a cycle and becomes a reason for the formation of a funnel cloud. The presence of instability in the atmosphere is avery important factor for the formation and development of tornodos. Tornodo normally form from a Super Cell. Thunder shower, hail storm, strong wind are some weather events occur with a tornodo. Tornodos form as a single tornodo or a family of tornodos and move in a straight line.

Detction of tornado by RADAR

Stout and Huff identified a tornodo cloud by the Hook form of RADAR echo present in the radar screen. But mostly the hook form of echo occurs only when a tornodo forms from cumulonimbus cloud, hence there will be not much time for giving tornodo warnings. But Doppler Weather Radar are very useful tools to detect the formation and movement of a tornodo.

Electrical and sound effects of a tornodo

Blue, bright and strong lightening is seen along with tornodo. Ball lightening is also seen sometimes. Due to continous lightening the funnel cloud portion is seen in yellow colour. As the funnel portion of the cloud touches the ground we hear a roar. Tornodo give a sound of one million bees.

Tornodos in India

The Scientists of India Meteorological Department have done research on the following tornodos.

Sl.No.	Tornodo’s		IMD Scientists who have done the research
	Date	Place of occurrence
01	19.04.1963	Coochbihar district and Golpara district of Assam	J. Nandy, A.K. Mukharji
02	13.05.1967	Kanpur, Uttarpradesh	Ranjit Singh
03	21.03.1969	Dimond Harbour, Kolkatta	A.K. Mukharji, Battacharya
04	07.11.1969	Kollur lake, Krishna district, Andhrapradesh	Ranjit Singh
05	10.03.1975	Ludhiana, Panjab	G.S. Balachandra, M.L. Balachandra
06	17.05.1976	Balasur district, Odisha	Ranjit Singh
07	17.03.1978	New Delhi	H.N. Gupta, S.K. Gosh
08	16.04.1978	Kionjar, Odisha	A.K. Gosh
09	18.04.1978	Nadia district, West Bengal	Ranjit Singh
10	17.04.1981	Kionjar district, Odisha	Ranjit Singh
11	06.04.1980	Raepalli, Tenali taluks of Guntur district, Andhrapradesh	K. Veeraraghavan, S.K. Subramanian, V. Venkateswaralu, N.S. Bhaskara Rao
12	07.02.1984	Chandrapadi (near Tarangampadi) Nagapatnam district and adjoining Karaikal region	N.S. Rajagopalan, S.A.H. Albeez and three others
13	19.10.1987	Chapra, Bihar	P. Prasad

Damages

Tornodo sucks all small objects over which the tunnel cloud portion of the tornado moves. Small bits of paper, dry leaves, wooden pieces, dusct particles, small fishes et are sucked like a pump, carried away with the rotating air coloumn and thrown away several kilometers away. Tornodo’s funnel cloud portion contains more or less empty space (like an eye of a tropical cyclone) inside and rotatinf air coloumn outside as a wall. The very small inner space has a cloud and weather less region. The outer wall region wind whirls going upwards. The updraft may have a speed of 100 to 120 meters per second. Hence when a tornado passes over a building or a house, due huge pressure gradient they are broken to pieces, lifted up by the rotating air, carried away by the moving tornado and thrown away at different places. Due to the pressue difference inside a tornado and its outside even the lids of bottles are flown away. The fur of sheeps and wings of birds are also plucked and thrown away.

There are some unbelievable incidents due to tornodos. A tornado which occurred at New Delhi on 17.03.1978 has lifted a passenger bus with 70 passengers and dropped it in a canal 20 meters away with its front portion down in the canal. This tornado lasted for only three minutes. But due to this 28 people died, 700 injured and property worth rupees 10 millon was damaged.

A tornado which formed in America 0n 30.05.1879 is considered as the most intense tornado. Records say that this tornado has removed a iron bridge of weight 108 ton from its holdings, rolled it into a ball and dumped it in a nearby 2 meter deep river.

The tornado which occurred in Kionjar district of Odisha on 16.04.1978 was accompanied with severe hailstorm. A hail of cricket ball size hit a farmer and broke his hip, another hail hit his ox and broke its neck. On 17.04.1981, a tornado formed in the same district killed 35 people and thousands of cattle. The Chapra tornado of Bihar on 19.10.1987 killed 20, injured 517 people and damaged 2773 houses. In Chapre town a two storey building at Roopganj Mohalla was lifted from ground and broken to pieces. A tornado which occurred on 07.02.1984 in Nagapatnam district. It was first seen at Boodhanoor village then moved to Sankaranpandal, Arasangudi and Nallathur. A bullock-cart of weight 15 tons was lifted to height of 150 feet and was thrown away at a distance of 800 feet. One person died in Bhoodanoor village due to wall collapse. This was reported as news item in the Indian Express as a news item titled as The Fury from the Sky.

Multiple vortex

A multiple-vortex tornado is a type of tornado in which two or more columns of spinning air rotate around a common center. A multi-vortex structure can occur in almost any circulation, but is very often observed in intense tornadoes. These vortices often create small areas of heavier damage along the main tornado path. This is a distinct phenomenon from a satellite tornado, which is a smaller tornado which forms very near a large, strong tornado contained within the same mesocyclone. The satellite tornado may appear to "orbit" the larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct circulation, and is much smaller than the main funnel.

Waterspout

A waterspout is defined by the National Weather Service as a tornado over water. However, researchers typically distinguish "fair weather" waterspouts from tornadic waterspouts. Fair weather waterspouts are less severe but far more common, and are similar to dust devils and landspouts. They form at the bases of cumulus congestus clouds over tropical and subtropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly. They occur most commonly in the Florida Keys and in the northern Adriatic Sea. In contrast, tornadic waterspouts are stronger tornadoes over water. They form over water similarly to mesocyclonic tornadoes, or are stronger tornadoes which cross over water. Since they form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are more dangerous. In official tornado statistics, waterspouts are generally not counted unless they affect land, though some European weather agencies count waterspouts and tornadoes together.

Landspout

A landspout, or dust-tube tornado, is a tornado not associated with a mesocyclone. The name stems from their characterization as a "fair weather waterspout on land". Waterspouts and landspouts share many defining characteristics, including relative weakness, short lifespan, and a small, smooth condensation funnel which often does not reach the surface. Landspouts also create a distinctively laminar cloud of dust when they make contact with the ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they can produce strong winds which could cause serious damage.

Similar circulations

Gustnado

A gustnado, or gust front tornado, is a small, vertical swirl associated with a gust front or downburst. Because they are not connected with a cloud base, there is some debate as to whether or not gustnadoes are tornadoes. They are formed when fast moving cold, dry outflow air from a thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a "rolling" effect (often exemplified through a roll cloud). If low level wind shear is strong enough, the rotation can be turned vertically or diagonally and make contact with the ground. The result is a gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage.

Dust devil

A dust devil resembles a tornado in that it is a vertical swirling column of air. However, they form under clear skies and are no stronger than the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. If there is enough low level wind shear, the column of hot, rising air can develop a small cyclonic motion that can be seen near the ground. They are not considered tornadoes because they form during fair weather and are not associated with any clouds. However, they can, on occasion, result in major damage in arid areas.

Fire whirls and steam devils

Small-scale, tornado-like circulations can occur near any intense surface heat source. Those that occur near intense wildfires are called fire whirls. They are not considered tornadoes, except in the rare case where they connect to a pyro-cumulus or other cumuliform cloud above. Fire whirls usually are not as strong as tornadoes associated with thunderstorms. They can, however, produce significant damage. A steam devil is a rotating updraft that involves steam or smoke. Steam devils are very rare. They most often form from smoke issuing from a power plant's smokestack. Hot springs and deserts may also be suitable locations for a steam devil to form. The phenomenon can occur over water, when cold arctic air passes over relatively warm water.

Intensity and damage

Tornado rating classifications[21][57]
F0 EF0	F1 EF1	F2 EF2	F3 EF3	F4 EF4	F5 EF5
Weak		Strong		Violent
		Significant
			Intense

The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. The Enhanced Fujita (EF) Scale was an update to the older Fujita scale, by expert elicitation, using engineered wind estimates and better damage descriptions. The EF Scale was designed so that a tornado rated on the Fujita scale would receive the same numerical rating, and was implemented starting in the United States in 2007. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.Doppler weather radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.

Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger. In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from sub-vortices.

In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes (EF4, T8 or stronger). Outside Tornado Alley, and North America in general, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America, respectively.