Thiruvananthapuram: The increasing occurrence of extremely heavy rains due to changes in cloud composition, is posing a threat to Kerala according to meteorological experts.
Of late the state has started experiencing a strange phenomenon. After the drop in the number of rainy days, Kerala has been receiving heavy rains. Experts say cloud bursts and climate change are triggering extremely heavy rains.
If a region receives 10 cm of rainfall in an hour, it is possibly caused by a cloudburst. But if the rainfall received over the same period is just 5 cm then it could be due to moderate cloudburst.
Earlier Kerala used to get 20 cm rain if it rained throughout the day. However, now instances of 5 cm rain/ hour have increased.
Experts say cumulonimbus clouds are responsible for the heavy rains that the state is witnessing nowadays. They fear that such rains received an area of 100 sq km could lead to floods. Moreover, it is difficult to predict cumulonimbus clouds and that compounds the threat.
Cumulonimbus clouds are formed due to intense low pressure or atmospheric instability. Global warming and climate change are also contributing to this climatic condition greatly.
Earlier, cumulonimbus clouds were not seen during the southwest monsoon in Kerala. Only normal monsoon clouds hovering at a height of 7 km used to be witnessed in the Kerala region. Though these clouds did not trigger extremely heavy rains, the state used to experience moderate rainfall for a continuously longer period.
But with the drop in the number of rainy days, the formation of cumulonimbus clouds increased. These clouds may extend up to an altitude of 12 to 14 km. When it develops vertically, this is the largest of all clouds.
Along with rains, these clouds bring seasonal winds. The high-velocity winds wreak havoc sometimes, uprooting trees and destroying agricultural crops. The average wind speed in Kerala during monsoon is 40 km per hour while winds caused by cumulonimbus clouds is 60 km per hour and it does not blow in a particular direction.
In the past thunder and lightning used to occur rarely in Kerala during the monsoon season. But now it is happening frequently due to cumulonimbus clouds which become heavy and motionless. Experts say while a moving cloud would not discharge lightning, a motionless thick cloud that covers a wide area tends to discharge electricity by lightning.
Kerala located on the west coast of India is experiencing changes in the composition of clouds and wind patterns. It was a short spell of intense rainfall which could also be described as a moderate cloud burst, that caused the flood in Kerala in 2019.
Met experts say that there is a need for conducting a detailed study to ascertain whether the extremely heavy rainfall experienced in Kizhakambalam in Ernakulam district, was caused by a cloudburst.
In the Himalayas, 5 cm of rainfall in an hour which could also be classified as a cloudburst, can cause huge destruction. The intense rains caused by cloudbursts in the Himalayas are categorised as "A".
The extent of the destruction is less if the rainfall is below 10 cm. However, the Konkan region used to experience destruction even after getting rainfall below 10 cm and that's how this phenomenon was known as moderate cloudburst.
Kerala CM asks people to brace up for rain fury
Thiruvananthapuram: Kerala Chief Minister Pinarayi Vijayan on Saturday asked the people in the State to gear themselves up in the wake of weathermen predicting heavy rain in the coming days.
Quoting them, he said a depression may form in the Bay of Bengal by July 21 and is likely to bring heavy monsoon showers.
Therefore, people should follow the weather forecasts and the departments should make necessary arrangements to face the monsoon rain.
"Climate experts have informed us of a depression that is likely to form in the Bay of Bengal by July 21. Such depressions usually strengthen the monsoon in the State. During the last few years, we received heavy rains due to such depressions," he said.
"We need to exercise caution in the coming days," he said.
The India Meteorological Department (IMD) and the Kerala Disaster Management Authority are closely monitoring the situation, he said.
The IMD's prediction for the next five days is that there would be heavy rains and it asks fishermen not to venture into the sea till July 18.
(With inputs from PTI)
