Image credit: Rana Dutta

The Indian Meteorological Department (IMD) has recently issued a weather forecast that  thunder squall accompanied with lightning of potential impacts to occur at isolated places over Assam & Meghalaya on
March 5 and 6, 2019.

The Weather Channels also predicted rain or snow accumulation in the east and Northeast India till Thursday evening.

The fury of nature has been left many parts of Northeastern region of India in tatters.  Incessant rainfall in most areas of Garo Hills in Meghalaya has left a trail of destruction with houses, schools and trees strewn in the aftermath of its destruction.

While some districts of Assam and West Meghalaya have been partially affected, the worst affected has been the districts of North and East Garo Hills in the state of Meghalaya.

Most lightning deaths and injuries occur when people are caught outdoors in the summer months during the afternoon and evening. Death from lightning strikes is now one of the most discussed issues in the country as majority of the victims are the lone bread earners of their families.

The maximum lightning incidents in the entire Indian subcontinent occurs in central Bangladesh and the states of Meghalaya, West Bengal and Assam during the pre-monsoon season (March-May) with 40 lightning
strikes per square kilometre.

The data of the National Crime Records Bureau (NCRB) says lightning kills more people in India than any other natural calamity. According to a 2014 NCRB report, out of 20,201 accidental deaths attributable to natural causes, 12.8 per cent were due to lightning strike.

In Bangladesh the lighting strike death toll is unbelievable. On last May 2018, 29 people have died from lightning in 12 districts in 24 hours and almost all of them are farmers.

Earlier at least 12 people died in March and 58 people died in April 2018 in parts of Bangladesh, according to government data. In the last two days of April last year, as many as 33 people died as storms swept across the country, said Disaster Management Minister Mofazzal Hossain Chowdhury Maya. The number of deaths was 160 in 2015, 170 in 2014, 185 in 2013, 201 in 2012 and 179 in 2011.

Lightning poses a major threat as an increasing number of people are losing life due to the natural disaster every year, experts say.

Scores of people die every year after being struck by lightning during the rainy season in Bangladesh, which runs from April to October, but officials say the numbers are exceptionally high this year. Every day 10-12 people are dying from lightning strike.

Authorities declared lightning strike a natural disaster after 82 people were killed in a single day in May 2016. Independent monitors estimated that some 349 Bangladeshis died from lightning that year. In Bangladesh, the thunderstorm usually occurs from March to May but sometimes it takes place until October or November. Owing to sudden change in weather, heavy rain and strong gales occurred in the Bay of Bengal. That had caused the lightning strikes and loss of lives in India as well.

The entire Bay of Bengal, a part of Assam, Meghalaya and West Best Bengal are prone to lightning because of its complex topography. Studies have showed thunderstorms are very frequent during the pre-monsoon season in northeastern India and Bangladesh. They are especially distinctive by their nature and severity compared to other thunderstorms, which occur over some other regions or during some other seasons.

Is climate change is responsible?

Now most of scientists believe that with the increase in global temperature, the intensity of thunderstorms and lightning will increase more.

The thundercloud formation because of excess heat over Bangladesh is resulting in thunderbolts and lightning, particularly in the regions where water bodies are high, such as Haor areas. The wind convergence results in an active convection which is the upward movement of warm and moist air. The subsequent instability results in widespread precipitation with chances of thunderstorms.

According to Prof Rashid, the temperature rose in April in Bangladesh, which has caused water vaporize and leads to rain, clouds, and lightning.

Bangladesh is witnessing increasing numbers of casualties from lightning, a natural disaster, for the last few days, mainly because of the rise in temperature that is leading to formation of upper air circulation in the geographical region, experts say.

The geographical location of Bangladesh with the Himalayas in the north, the Bay of Bengal in the south, as well as the Indian Ocean and Arabian Ocean in surrounding areas, is adding to the creation of thunderstorms in the country.

It is to be noted that Northeast India, together with Bangladesh, is one of the most thunderstorm-prone regions in the world. This was found by Tetsuya Fujita of the University of Chicago in 1973.

Fujita along with Allen Pearson had developed the Fujita Pearson Scale for measuring damage caused by tornados. Of all the severe thunderstorm events in the Northeast region during the 55 years of study period,
about 30 per cent of the events resulted from squalls (nor’easters),  with hail and lightning accounting for 18 per cent and 10 per cent of all recorded events.

While severe thunderstorms can develop at any time of the year, over half of the severe thunderstorm events occurred in the region during March, April and May, peaking during the latter months.

A secondary peak in severe thunderstorm events occurs in September, and is likely due to the impact of tropical cyclones or their remnants flowing from the warm waters of the Bay of Bengal.

The data compiled by the ICRC on the occurrence of severe thunderstorm incidents show that they are first seen on an isolated day in the month of February under the influence of a western disturbance, and it becomes a familiar feature during the hot afternoons of April to May to early morning hours of the next days.

Summer monsoon season with 60 per cent incidents is the most favoured time of the year for occurrence of lightning strikes in Assam, followed by pre-monsoon season with 32 per cent of the incidents.

During the 55-year study period, it was found that 22 people died on an average per year from severe thunderstorm hazards in Northeast India. More than 60 per cent of these death cases were due to lightning.

In general, severe thunderstorm impacts like loss of life and injury, loss of livelihood and damage to infrastructure are significantly more on impoverished and vulnerable rural population in the western part of Assam.

According to Rahul Mahanta of Cotton University, a total 454 cloud and ground (CG) lightning strikes were observed in Assam during the entire period of their study, with a mean of 12.6 CG lightning strikes
per year.

The total climatology of lightning activity showed that the western region of Assam experiences higher lightning activity. The minimum lightning activity is found to be occurring in northeastern and eastern parts of the region.

Another study published in the International Journal of Climatology in September 2015, which was carried out by Hupesh Choudhury, Partha Roy, Sarbeswar Kalita and Sanjay Sharma states that during the pre-monsoon season, the frequency of lightning is quite significant in the Northeast due to the interaction of moisture-laden wind with the complex topography of the region. The Meghalaya plateau and foothills of Patkai hill range, in particular, experience severe lightning.

Iqbal R Tinmaker and Kaushar Ali of the Indian Institute of Tropical Meteorology finds almost same result attributed to space time variation of lightning activity over Northeast India.

They revealed lightning flash rate density is maximum over the west of northeast India. The study, published in Meteorologische Zeitschrift in April, 2012, said this high flash rate density is attributed to the topography and the geography of the region, along with the moisture availability.

The 2014 report published by Indian Meteorological Department (IMD) said the highest number of thunderstorms in each month of the storm period (March 15 to June 15, 2014) were recorded in Assam, followed by Arunachal Pradesh in March, Meghalaya in April and Tripura in May and June. During the entire period, the frequency was highest during night  (30 per cent) followed by evening (21 per cent).

Lighting casualties are increasing because of lack of awareness among people.  We find that many illiterate people still believe lighting as well as thunderstorm to be a super-natural phenomenon or God’s fury.

Awareness is very important to reduce the toll and its harmful impact. Routine research works involving government and NGO and government regulation are needed mitigate the menace.

The Bangladesh government is deeply concerned about the peril of such incidents. However, Assam as well as Meghalaya government seem quite indifferent to it.

Mohan Kumar Das, senior research fellow of the Institute of Water and Flood Management (IWFM) at Bangladesh University of Engineering and Technology (Buet), said deaths from lighting could also be avoided if people take some cautious steps according to BMD.

Despite being the most lightning-prone zone in the Northeast, Assam does not have any separate programme to create awareness among the people about lightning and TS. The state revenue and disaster management authority does not have any separate campaign for lightning.

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