A barrage of phenomenal lightning strikes associated with dangerous thunderstorms during the ongoing Kalbaisakhi (pre-monsoon) season have claimed 59 lives, during the week ending April 24, across the familiar stretch in East India - Andhra Pradesh, Odisha, West Bengal, Jharkhand, Bihar, Uttar Pradesh.

An extended period from February 21 to April 25 (64 days) has seen more than 200 deaths due to lightning in Uttar Pradesh, Bihar, Jharkhand , Odisha, and Madhya Pradesh, according to a Kalbaisakhi bulletin issued jointly by the Climate Resilient Observing Systems Promotion Council, the India Meteorological Department (IMD) and World Vision India.

Thunderstorm raids East Coast

In fact, Saturday and Sunday saw a rare but dangerous thunderstorm raiding the East Coast from Andhra Pradesh, Telangana, Tamil Nadu and Karnataka in a South-South-West direction producing massive lightning strikes and moderate to heavy rainfall across the region. From South-Central Tamil Nadu and adjoining Karnataka, the thunderstorms crossed the Western Ghats and entered Kerala lighting up the evening skies on Sunday and generating a wet spell before dissipating over the Arabian Sea.

Kalbaisakhi extends from March till the South-West monsoon establishes over North- East India. Based on event descriptions and the meteorological environments involved, it appears that the causative dry north-westerly winds (also called "nor'westers") boosted by passing western disturbances, may have packed progressive ‘derechos,’ the bulletin said.

Beneficial rain for crops

Derecho is a Spanish word which literally means ‘straight’ and is taken here to mean a widespread, long-lived, straight-line wind storm associated with a fast-moving group of severe thunderstorms. Derechos can cause hurricane-force winds, tornadoes, heavy rain, and flash floods. In many cases, convection-induced winds take on a bow echo (backward ‘C’) form of squall line, often forming in a region abounding in rich low-level moisture (from the Bay of Bengal) and warm-air advection (horizontal movement).

On extremely rare occasions, tornadoes may accompany the thunderstorms, lightning, and hail. Flying through these winds can be extremely dangerous. Circumnavigating or penetrating them may be disastrous and pilots avoid them. However, the rainfall from these storms is beneficial for the tea cultivated in Assam and for the jute and rice and tea cultivated in West Bengal and Bangladesh. The associated thunderstorms move generally from West to East.

The CROPC and the IMD have been monitoring the season and initiated comprehensive lightning safety programme in the form of a Lightning Resilient India Campaign. The campaign offers a series of services to states all through its network of government and non-government agencies, volunteers and academia.

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