Cloudbursts

Context

Sudden, “highly-localised rains” in Amarnath, Jammu and Kashmir caused flooding and led to the deaths of at least 16 people and injuries to more than 20 others.

What is a cloudburst?

• India Meteorological Department definition- The India Meteorological Department (IMD) defines it as unexpected precipitation exceeding 100mm (or 10 cm) per hour over a geographical region of approximately 20 to 30 square km. 
• Extreme rainfall in short period- A cloudburst refers to an extreme amount of rain that happens in a short period, sometimes accompanied by hail and thunder.
• Criteria for cloudburst- All instances of cloudbursts involve heavy rain in a short period, but all instances of heavy rain in a short period are not cloudbursts if they do not fit this criterion.

Why do cloudbursts occur in hilly areas like Amarnath?

• Terrain and elevation- Cloudbursts are more likely to occur in mountainous zones mainly because of terrain and elevation.
• Mechanism that works in hilly areas- In hilly areas, sometimes saturated clouds ready to condense into rain cannot produce rain, due to the upward movement of the very warm current of air. Instead of falling downwards, raindrops are carried upwards by the air current. New drops are formed and existing raindrops increase in size. After a point, the raindrops become too heavy for the cloud to hold on to, and they drop down together in a quick flash.
• Relative humidity and cloud cover- A study published in 2020 examined the meteorological factors behind the cloudburst over the Kedarnath region. It found that during a cloudburst, the relative humidity and cloud cover was at the maximum level with low temperature and slow winds.