A cloudburst is a localised but intense rainfall activity. Short spells of very heavy rainfall over a small geographical area can cause widespread destruction, especially in hilly regions where this phenomenon is the most common.
A cloudburst has a very specific definition: Rainfall of 10 cm or more in an hour over a roughly 10 km x 10-km area is classified as a cloudburst event.
Cloudbursts are not uncommon events, particularly during the monsoon months. Most of these happen in the Himalayan states where the local topology, wind systems, and temperature gradients between the lower and upper atmosphere facilitate the occurrence of such events.
Mechanism and occurrence of cloudburst
1. One of the most important aspects of cloudbursts is that the Orographic lift is the primary cause of it.
2. The terrain region (orographic barrier) pushes the saturated clouds (Moisture laden air mass) upwards along the mountains.
3. The moist air mass is rapidly pushed up. It reaches relative humidity of 100% i.e. the air mass is completely saturated with water and cloud formation starts.
4. This rapid updraft movement of warm and moist wind forms the Cumulonimbus clouds.
5. Eventually, when it becomes difficult to hold on to so much water vapour and raindrops in the cloud, it sheds water with great strength and velocity.
Recent incidents of cloudbursts in India
1. Cloudburst occurred above Salem district, Tamil Nadu. This resulted in 213 mm rain in a single day. Ponds in the area filled up and so did the Thennakudipalayam lake. The Vasishta Nadi became flooded, making the Attur check dam to brim with water.
2. The most recent cloudburst occurred July 2022 near the Holy cave Shrine of Amarnath in Jammu and Kashmir in which at least 16 people were killed and many still missing.
Conclusion: Can cloudbursts be forecast?
The India Meteorological Department forecasts rainfall events well in advance, but it does not predict the quantum of rainfall — in fact, no meteorological agency does. The forecasts can be about light, heavy, or very heavy rainfall, but weather scientists do not have the capability to predict exactly how much rain is likely to fall at any given place.
Additionally, the forecasts are for a relatively large geographical area, usually a region, a state, a meteorological sub-division, or at best a district. As they zoom in over smaller areas, the forecasts get more and more uncertain.