Kalbaishakhi-কালবৈশাখী

[Kalbaishakhi is mentioned in the eleventh chapter of the fifth-grade elementary science book.]

Kalbaishakhi (কালবৈশাখী) Nor’wester is a type of thunderstorm that usually blows over Bangladesh from the northwest in April-May (Baishakh). Locally, this thunderstorm is better known as Kalbaishakhi. The word ‘Kaal’ also means season and also black color. Kalbaishakhi is sometimes referred to as ‘Kalobaishakhi‘.

This means the black Baishakhi cloud. The destroyer is also called ‘Kal‘. That is why the name of this storm is due to its thick black clouds, thunderstorms, and its destructive nature. The arrival of this storm occurs hand in hand with the summer season. Locally, when the surface of an area is heated by extreme temperatures or other causes, the atmosphere becomes quite unstable and this storm is born.

In April-May in Bangladesh and adjoining areas, the occasional thunderstorm with occasional thunderstorms in the afternoon is called Kalbaishakhi. It is called Norvester in English as it flows from the northwest.

When the surface air of this subcontinent gets too hot, the air becomes light and unstable. The heated light air rises straight up and cools to form cumulus clouds. As the atmosphere continues to fluctuate, cumulus clouds form vertically black clouds called cumulonimbus and subsequently produce thunderstorms. The main difference between Kalbaishakhi and a normal storm is that with this storm there is always lightning and thunder.

The life cycle of Kalvaishakhi can be divided into three stages cumulus or concentration stage, maturity stage, and dispersion stage. After 30 to 45 minutes of a Kalvaishakhi maturity, its intensity begins to decrease and it enters the scattering stage. Extremely rapid temperature drops, the presence of large amounts of water vapor in the clouds, and the accumulated upward movement of air cause hailstorms to accompany the solstice. Excessive hailstorms cause extensive crop damage.