What is the astonishing reason behind Chennai receiving the highest rainfall in over 6 years?

Chennai rainfall- 

We all know that our country witnessed a delayed monsoon this year. The monsoon rains started as last as in September, and in many parts of the country, the rainfall is still going on. This delayed monsoon is a direct result of climate change followed by a sudden shift in weather.

Some parts of the nation suffered a lack of rainfall this year, while on the other hand, some parts of the country witnessed a very high rainfall. One city even saw the heaviest rain since 2015, which seems shocking as many towns that expected heavy rain did not receive the desired amount—the city which received its heaviest rainfall since 2015 and is our topic for today in Chennai.

Chennai, a city of the South Indian state Tamil Nadu witnessed its highest rainfall since 2015 this year. The state has seen a sudden increase in its rainfall levels as it received a continuous pouring for straight 24 hours. On the night of Saturday, October 6, the city witnessed an incessant heavy rainfall that lashed the whole town in just twenty-four hours.

The overnight rain, which is recorded to be the heaviest in the city after 2015, was part of a formation of low pressure over the Bay of Bengal. This heavy pouring directly resulted in flooding at most minuscule 40 busy commercial as well as residential neighbourhoods. Let us now know what did the overnight rain caused in detail.

The heavy rain that continuously poured on Saturday night and Sunday morning caused waterlogging and flooding in several city neighbourhoods, including areas such as T Nagar, Vyasarpadi, Adyar, Velachery, Royapettah and Mylapore. All these areas were filled with water after the overnight rain.

Moreover, areas such as Jawaharlal Nehru Nagar, Madhavram, Tondiarpet High Road, Royapuram, Khadar Nawaz Khan road, interior Velachery regions and many other regions of the city suburbs were among those areas which either reported water flooding or water inundation in the early morning of Sunday, after receiving heavy pouring for the whole night.

According to the reports of the Government, near about 500 cusecs of water from the Puzhal reservoir will be released around the time of 11 in the morning. This was followed by the local authorities giving alerts to the people living in the low lying habitations on the banks of the surplus canal. The Government made further announcements that the Chembarambakkam reservoir will be released by 1.30 pm on Sunday.

What was the level of rain in the said areas of Chennai?

As per the data provided by two rain recorders, Nungambakkam in Chennai city and Meenabakkam in city suburb clearly showed that the city recorded very high levels of rainfall on this Saturday. The story of rains in the city and the city suburb was 21.5 cm and 11.3 cm respectively by 8:30 am on Sunday, which is extremely heavy.

As per the records of the year 2015, the city received the heaviest episodes of rain on November 15 and 16, in which the city of Chennai recorded a very high 24.6 cm in just 24 hours, which indicates how heavy the rainfall was. It resulted in severe flooding and waterlogging in many parts of the city, just like the recent rain.

The precipitation of 2015 broke the previous record of 14.6 cm, recorded in November 2005; it is by far the heaviest rainfall recorded in the 2000s. The recent rain of 21.5 cm in Chennai is the second richest after the precipitation of 2015.

However, looking at the heaviest ever rainfall recorded in the city in 24 hours and not just in the 2000s, the town has even recorded rainfall as rich as 45.2 cm, recorded in November 1976. Another rainfall that was recorded to be the heaviest in two days was the rainfall of November 1985 in the city when the measurements were 25cm on November 12 and 33 cm on November 13, which is extremely heavy.

Chennai’s rainfall pattern

The monsoon in Chennai is mainly about the Northeastern monsoon. The Northeastern monsoon, which is also known as the primary monsoon of Tamil Nadu, brings a sufficient amount of rainfall to the whole state. A large majority of states depend upon the Southwestern monsoon, which occurs from May to July.

During this season, the city of Chennai witnesses rainfall from October to December, with the easterly winds beginning from the middle of October, which precisely takes place between October 10 and 20.

However, the state of Tamil Nadu depends solely on the Northeastern rainfall. However, the southwestern monsoon also helps the state of Tamil Nadu by maintaining a sufficient amount of groundwater level. Moreover, the Coastal regions of the state of Tamil Nadu receive about 60% of the annual rainfall from the northeastern monsoon season, while the interior districts get about 40 to 50 per cent of their precipitation from this northeastern rainfall. Therefore, it is evident to everyone that the northeast monsoon plays a significant role in bringing much-needed rain to the whole state of Tamil Nadu.

Moreover, this is not the end of this seasonal rainfall. According to the predictions made by the meteorological department of the state, there will be a formation of low pressure over the Bay of Bengal, which will move towards the northern coast of Tamil Nadu, which ensures a moderate level of rain in the upcoming days in the city of Chennai and many other cities of Tamil Nadu.

As per the data provided by the officials of the meteorological department, an upper air cyclonic circulation lies above southeast of Bay of Bengal and adjoining equatorial Indian ocean extending 3.1 kilometres above the main sea level. Therefore, due to pressure made by this, a low-pressure area is likely to form over the southeast of the Bay of Bengal. Moreover, the predictions suggest chances of stormy winds of 40 to 50 kilometres which might prevail over the sea.

At last, a heavy rainfall warning has also been given in the city of Chennai for Wednesday, which is November 10, as a thunderstorm along with serious to weighty rainfall is likely to occur at isolated places over Chennai as well as many other cities of Tamil Nadu such as Tiruvallur, Cuddalore, Kancheepuram, Chengalpet, Villupuram, Nagapattinam, Tiruvarur, as well as Pudukottai districts of Tamil Nadu, along with Puducherry and Karaikal.

The rainfall recorded in the 24 hours was very high, and it is very confident that it will help in levelling up the groundwater levels in the city of Chennai. However, this also raises the problem of waterlogging and flooding, which can make the condition of the city terrible. Moreover, the upcoming heavy rainfall predicted by the meteorological department states how much the city will witness heavy pouring. Therefore there is a strong need for the Government of Tamil Nadu as well as officials of the town to take quick and efficient action to prevent flooding in the town.

edited and proofread by: nikita sharma