Many parts of Maharashtra including Mumbai and Konkan experienced extremely heavy rainfall in the past week, while the situation in Chiplun was quite grave. The flooded rivers of Vasishthi and Shiva engulfed Chiplun city. Water entered many parts of the city, submerging even the internal roads. With the occurrence of extremely heavy downpour, discussions regarding cloud burst and the news related to it were getting circulated on the social media. In the coastal areas, normally the incidents of cloud bursting do not occur. Cloud-bursting is primarily experienced in high-altitude regions. Intent of this article is therefore to explain the meaning of cloud-bursting and how does it occur.
The beginning of the process of cloud-bursting
Clouds that cause thunder and bring torrential rains contribute to this process. These clouds are called ‘Cumulonimbus’. It is a Latin word. ‘Cumulus’ means coming together and ‘nimbus’ means clouds. In short, the accumulation of rainy clouds in a rapid manner is the initiation of this process.
The water content in clouds increase owing to hot air and humidity. Billions of water droplets get dispersed in these clouds which leads to heavy rains. Sometimes, a column of upward moving warm air gets created in these clouds, which is known as ‘updrafts’. This column of air carrying water droplets keeps on going higher and higher. While traveling upwards in the column of air, the size of the water-droplets sometimes become more than 3.5 mm. Sometimes in this upward-going column of air, rapid air currents are created, and small storms are generated in those clouds and the water droplets get caught in those storms. The more the power of the air current, higher the altitude it reaches, and thereafter it descends rapidly like the cradles of a merry-go-round. The big water-droplets held by the air column come down in a high speed to the ground. The air column descending towards the ground is called ‘downdraft’. The speed of water droplets is 12 km per hour initially and it later increases to 80-90 kms per hour.
The actual process of cloud-bursting
Even if a cloud is big, its spread is not as big; therefore, it appears as if a column of rain has fallen on a small piece of a land. The word cloud-bursting itself gives its clear meaning. If the entire base of a water tank is taken out, the water from that tank will fall with speed; similar is the process in cloud-bursting. Only difference in this case is that there is a huge cloud filled with water spread over several miles and has millions of gallons of water. The water cloud literally bursts and in a very short time, comes down heavily like a column of water with catastrophic force; destroying everything that comes in its way due to the big water droplets and fast speed. This fall of water is devastating to trees, small animals, weak buildings, etc. The capacity of the land to absorb water is different in different parts and it also takes time to absorb water. A huge quantity of water falls in few minutes at the time of cloud bursting; therefore, the process of absorbing water by land completely stops, creating a widespread flood-like situation. If cloud-bursting takes place in a hilly region, the water flowing down the hill brings huge amounts of soil towards the base of the hill. The cumulative effect of the speed, size of water droplets, and air column carrying water crashing on the ground in the event of cloud bursting causes immense damage.
A unique incident occurring at the time of cloud-bursting
A unique incidence occurs at the time of cloud-bursting. The weather is cloudy before such cloudburst. It starts getting dark, but the darkness reduces as it starts raining. Sometimes, it appears like it is raining in the sunshine; its reason being big sized rain-droplets. These droplets work like a mirror; refracting light; therefore, light seems to be more than usual.
The copious rainfall that occurred
on 26th July 2005 in Mumbai was a kind of cloud-bursting!
Cloud-bursting is not new to regions like the Himalayas. Though such incidents occur many times in the Himalayan region, it doesn’t become news probably because it happens in the remote hilly region. When it happens in human habitats, it immediately draws our attention. The heavy rains that hit Mumbai on 26th July 2005 was a type of cloud-bursting. Such a situation, however, gets rarely created as it happened in a coastal area. Mumbai witnessed rain fall of 950 mm in 8 hours.
The biggest event of cloud-bursting
The August 6, 2010 cloudburst in Leh is considered to be the largest cloudburst event in the world. The rainfall that occurred was 2 inches in 1 minute. Nowhere in the world has it rained so heavily so far.
Few major incidents of cloud-bursting
Virginia, America (24th August 1906) 234 mm rain in 40 minutes
Portobello, Panama (29th November 1911) 61.72 mm rain in 5 minutes
Plumb Point, Jamaica (12th May 1916) 198.12 mm rain in 15 minutes
Curtea, Romania (7th July 1947) 205.74 mm rain in 20 minutes
Barot, Himachal Pradesh (26th November 1970) 38.10 mm rain in 1 minute