What Is A Nor’wester? The Thunderstorm, AKA Kalboishakhi, Endemic To Eastern India, Bangladesh
What Is A Nor'wester? Kalbaishakhi, or Nor'wester, is a fierce thunderstorm unique to eastern India during the pre-monsoon season.
The year's first kalbaishakhi is set to hit Bengal and a few other parts of eastern India on Thursday evening. Essentially a fierce thunderstorm, the weather phenomenon is unique to the eastern and northeastern parts of India and Bangladesh. Kalbaishakhi (Bengali: কালবৈশাখী) is known as Nor'wester in English.
What Is Kalboishakhi Or Nor'wester?
The dramatic weather phenomenon known as the 'Nor’wester' takes the centrestage every year as the pre-monsoon season dawns on eastern and northeastern India. Locally referred to as 'Kalbaishakhi' in Bengal, these thunderstorms are more than just meteorological events — they are a spectacle of nature’s power, often leaving behind a trail of destruction.
A Nor’wester is a convective thunderstorm that typically originates in the northwestern direction, hence its name. A convective storm works on the principle of convection wherein warm and less dense air rises and cooler & denser air sinks to take its place, creating a circulation pattern. Such storms are most common between March and May, affecting regions like West Bengal, Assam, Odisha, Jharkhand, and Bihar.
Characterised by violent squalls, thunder, lightning, and torrential rain, they often strike during the late afternoon or early evening hours. Their sudden onset and intensity make them both awe-inspiring and dangerous.
How Do Nor’westers Form?
The formation of these storms is rooted in the collision of contrasting air masses. Dry, land-based air from the northwest meets warm, moist maritime air from the Bay of Bengal. This interaction creates instability in the atmosphere, leading to the rapid development of cumulonimbus clouds.
Cumulonimbus clouds usually have very high mass and form in the lower troposphere, which is around 10 km from the Earth's surface. Such clouds can form as low as 4 km away from the Earth. These towering clouds can extend up to 12 kilometres in height and 4 km unleash winds reaching speeds of 130-150 kmph. In some cases, Nor’westers even produce tornado-like conditions.
Local Impact And Cultural Significance
In Bengal, kalbaishakhi translates to "calamity in the month of Baisakh", reflecting the storm’s destructive potential. These thunderstorms are notorious for damaging crops, uprooting trees, and causing fatalities due to lightning strikes.
Despite their ferocity, eastern India waits for these storms as they bring relief from the scorching summer heat and replenish groundwater levels.
Due to the Nor'westers' unpredictable and destructive nature, a need for deep research was felt. Due to this, the Government of India decided to establish a dedicated research testbed to study Nor’westers. Located in Odisha’s Bhadrak district, this facility will employ advanced tools like drones and meteorological towers to track thunderstorms from their inception to dissipation.
The goal is to improve forecasting accuracy and issue timely warnings to minimise loss of life and property.
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