Thunderstorm
Topic: Air Masses, Fronts, Cyclones and Thunderstorms · NCERT: Class 11, Ch 9 "Atmospheric Circulation and Weather Systems"
Meaning
A thunderstorm is a short, violent local storm that comes from a fully grown cumulonimbus cloud (a tall, dark rain cloud). It forms on hot, humid days through intense convection, which means warm, moist air rises very strongly. Strong updrafts (rising air currents) make the cloud grow taller. Where the cloud top reaches heights below freezing, hail forms. Later, downdrafts (sinking air currents) bring cool air and heavy rain to the ground, often with thunder and lightning. If the air has too little moisture, the storm may raise a dust storm instead of rain.
Example
In April–May, nor'westers (called kalbaisakhi locally) bring sudden thunderstorms with strong winds and heavy rain to West Bengal and nearby states. In north-west India, the drier versions are the dust storms called andhis.
Don't confuse with
- Tropical cyclone: a tropical cyclone is hundreds of kilometres wide, forms over warm seas and lasts for days. A thunderstorm is a local storm that lasts only a few hours.