Sunday, March 29, 2015

Tornado in outskirts of Chennai on September 2013

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. They are often referred to as twisters. 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 180 km/h. Most extreme tornadoes can attain wind speeds of more than 480 km/h. The scale of intensity for Tornado is given below.

Tornado in India

The areas of  occurrence of tornadoes in India are given in fig below. About 72% of the reported tornadoes in India have occurred in northeast India and Bangladesh.

About 76% of the tornadoes in India occur during March to May, the most favored month being April (see fig below) More number of tornadoes have occurred in the afternoon and evening. 72% of tornadoes are associated with “KalBaishakhi”.

F-3 Tornado in Odisha on March, 2009

During noon of 31st March 2009, A Tornado ravaged Odisha, a high winds damaged the villages in a narrow track of about 600 metres wide upto 6 kilometers long from the origin. The intensityof the tornado increased gradually and was maximum over Baghabuda. The tornado also passed over the water bodies like ponds in the villages, as fishes weighing 1-2 kg were found scattered. The photo of the the Tornado was put up in Odisha Diary.

It was an F-3 category Tornado, you can see the funnel upto the surface. It caused huge devastation and loss of life in Odisha. Lets now see Chennai's Tornado in 2013.

Possible F-0 Tornado in outskirts of Chennai September, 2013

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.

Chennai's Twister

So what was is it in Uthandi in outskirts of Chennai was it only a funnel cloud or did it have surface winds from the funnel cloud. The day was September 12, 2013, and the time was 4.30 pm. Robert Gagarin (58) of Uthandi happened to be on the rooftop of his house in time to catch a glimpse of a tornado in the distance.
“The sky turned pitch dark and I saw a circular cone shaped cloud formation for about 15 minutes. I clicked some pictures and also a video with my smart phone,” says an excited Robert according to Deccan Chronicle.

IMD Chennai's View

Met officials confirmed that Robert Gagarin had indeed seen a tornado, the first one reported in Chennai. “Our officials, who were on their way to Puducherry too experienced some effects of this phenomenon but we confirmed it only after seeing the picture” Dr Y.E.A. Raj, Deputy Director General of Meteorology, Regional Meteorological Centre (RMC), Chennai, told the Deccan Chronicle.

“We were able to support the photos of tornado with the pictures recorded in the DWR. It was possible only because of the continuous monitoring of the weather using the Doppler Weather Radar that detects rain clouds and squally winds perfectly up to 25 km” said Dr Y.E.A.Raj, Deputy Director General of Meteorology, Regional Meteorological Centre, Chennai.

According to S.B.Thampi, director, DWR, Chennai, a strong convictive cloud passed through that area on September 12, 2013. He added that he found a tornado vortex signature (TVS) on the Doppler Weather Radar on September 12th evening, which helped them to confirm the track and the location of tornadic rotation after he learnt about the uncommon phenomenon.

Dr Y.E.A, Raj too says there was a definite disturbance during the time mentioned on ECR Road. “We not only encountered intense weather, but our officials, who were travelling in a car to Puducherry  felt the vehicle being jolted to the left of the road. It may not have been an intense tornado as the funnel clouding did not extend to the ground, but  it was unmistakably a tornado,” he concludes.
    Eitherway it was one hell of event which we Chennaites may never hear till their lifetime. Cheers to Robert Gagarin who had the passion to take snap of the once in a life time event.

    Atacama Desert in Chile, the world driest place gets heavy rainfall after 80 years

    World Driest Place

    It's hard to overstate just how arid the Atacama, a plateau on the coast of northern Chile, really is. The Andes Mountains work like a 13,000-foot-high wall, completely blocking systems of moist air that might otherwise wander down from the Amazon Basin. As a result, the entire Atacama, a strip of land 1,000 miles wide, is virtually rainless.

    Arica, one of the desert's largest cities, receives an average annual rainfall of 0.76 mm, about the height of a flea egg.

    There are weather stations in the Atacama that have never recorded any rain. The town of Calama went without a single drop of rain from 1570 to 1971—more than 400 years.

    Historic Rainfall after 80 years in March 2015

    The area had seen years of drought, with the last major rainfall in 1997. But this year march rainfall are the heaviest in 80 years.

    Thunderstorms brought the equivalent of 7 years of rain to Chile's Atacama desert region and caused deadly flooding on last week of March, 2015.

    Antofagasta, Chile, where the annual average precipitation is 2 mm, saw 24 mm of rain in 12 hours.

    Communities in the desert region were struggling to cope with a disaster that knocked out power and cut off roadways. Thunderstorms with torrential rains moved into the Atacama, causing the Copiapo river to overflow its banks.

    Sunday, March 22, 2015

    Its Thunder storm season India - A special write-up from Tamil Nadu Weatherman

    The Pre-monsoon season or Hot weather or summer season is the names you would have heared in text books. The temperatures, particularly the maximum, during this season are very high over most parts of the country especially over central and northwest India. But there are many other Names called in different parts of India. This is also one of my favorite seasons to track weather.

    Kali Andhi

    Convective dust-storms occur over northwest India during the premonsoon season. In Africa and Arabia this phenomenon is called as Haboob. Sometimes, the distance between the cumulonimbus cloud and the associated Andhi dust-wall on the ground can be as large as 30 Km. The dust raised by strong wind reduces horizontal visibility to less than 100 meters. It may quickly build up out of the blue, transforming the dry hot afternoon into a dark brown mush. The assault of the Andhi usually lasts only a few minutes. North India often get affected by these Kali Andi every year. They are also called as black storms - Last year (2014) Delhi got hit by one of the Kali Andhi -

    Loo winds

    The Loo mainly originates in the large desert regions of the northwestern Indian subcontinent: the Great Indian Desert, the Cholistan Desert and the desert areas of Southern Balochistan. The plains of North India and Pakistan are both very hot and extremely dry during this season, water evaporates quite readily.  Loo direction is from west  to  east  and  they  are  usually  experienced  in  the  afternoons and its temperature varies between 45°C to 50°C. Entire North and north west India gets affected by Loo.  It makes life miserable for the people and the heat wave takes its toll and many people die because of it.

    Kalbaishakhi / Norwestor

    Moisture inflow from bay of bengal coupled with the heating of air, cold advection at 500 hpa and and presence of a jet stream between the levels 300 mb and 200 mb are extremely helpful for the occurrence of nor’westers. They normally form over Jharkhand and Bihar and travel entire East India affecting Odisha, West Bengal, Bangladesh. If u track the radar u can see  derechos too. Tornados too form in this period.

    Last year Bangladesh got hit by one of the norwestor and it overturned a train -

    Tornado in Odisha (rare image too) in 2009 -


    It is similar to Norwestor or it is a other name of Norwestor. The local severe storms of Assam and North East India during the pre-monsoon season are termed as Bordoichila, meaning the angry daughter of Assam. Advection of warm air in the lower levels and cold air in the upper levels increases the conditional instability in the atmosphere and favor the outbreak of severe thunderstorms.

    The southerlies approaching the north–east India, originate from the Bay of Bengal and thus, are warm and moist  On the contrary, the westerlies originating from the Tibetan plateau and eastern Himalaya are cold and dry. At nighttime while the Garo, Khasi and Jaintia hills cool down more rapidly than the plains, the katabatic wind blows down the slope toward the valley. This, in turn, brings down the moist air to the valley and a front-like structure develops during the nighttime, having two different types of air masses on—either side and this causes severe thunderstorms to occur over the valley mostly during the nighttime. North Eastern states mostly, Assam, Meghalaya Tirupura gets affected by these storms.

    News of Bordoichila in 2013

    Mango Showers

    Mango shower occurs along Kerala, Karnataka and also in parts of Tamil Nadu. The showers prevent the mangoes from dropping prematurely from trees and are crucial for the mango cultivation in South India.

    Mango Showers -

    'Cherry Blossom’ or ‘Coffee showers’

    It is a local wind that blows over the interior Karnataka during the hot weather season and is extremely helpful for coffee cultivation. The Hills in the interior Karnataka gets most of these rains. -

    Blossom or Coffee Showers -