Context: Earlier this week, powerful pre-monsoon thunderstorms (locally known as Andhi) tore through Uttar Pradesh, claiming over 100 lives, with Prayagraj, Mirzapur, and Bhadohi being the worst-hit districts.
About Andhi:
What it is?
- Andhi is the meteorological term for intense, convective dust storms or thunderstorms that occur predominantly during the pre-monsoon season in Northern India. These severe atmospheric disturbances are characterized by a sudden drop in temperature, blinding dust clouds, torrential rain, violent lightning strikes, and destructive gusty winds.
Primary Zone: The Indo-Gangetic Plains of Northern India, particularly stretching across Uttar Pradesh, Rajasthan, Haryana, Delhi, and Punjab.
How it Forms?
- Intense Surface Heating: Extremely high summer temperatures exceeding 45°C created a severe low-pressure zone over the land, causing the surface air to rapidly heat up and expand.
- Moisture Influx: Strong southeasterly winds pumped high levels of humidity from the Bay of Bengal across Uttar Pradesh, making the rising air highly volatile and moisture-laden.
- Upper-Atmosphere Instability: Active Western Disturbances (eastward-moving, extra-tropical storm systems originating over the Mediterranean/Caspian Sea) introduced a layer of cool, dry air in the upper troposphere.
- Convective Updrafts: The dramatic contrast between the blistering, moist air at the ground and the cool, dry air aloft created severe atmospheric instability. This acted as a classic trigger, forcing the warm air to shoot upward violently, condensing rapidly into massive, energy-dense cumulonimbus clouds.
Key Features:
- Extreme Wind Velocities: While typical Andhi events register wind speeds of 40–60 kmph, the recent event recorded devastating speeds between 100 kmph and 130 kmph.
- Violent Projectiles & Structural Collapse: High wind speeds turn loose objects into hazardous flying projectiles, uproot ancient trees, topple high-tension electricity poles, and cause weak brick walls and billboards to collapse.
- Dispersed and Localized Pockets: Unlike tropical cyclones, which track linearly from the sea to coastlines, these thunderstorms are highly localized, occurring in scattered, multiple pockets simultaneously over a vast landmass.
- Nowcasting Window: These storms develop rapidly, giving meteorologists a very narrow window (usually a few hours) for real-time tracking and issuing specific local alerts (Nowcasts).
