What is the Northeast monsoon wreaking havoc in Tamil Nadu?

The Northeast monsoon, which commenced over Tamil Nadu on Saturday, accounts for 48 per cent of the state’s annual rainfall. Schools and colleges in nine districts in Chennai declared a holiday as heavy rains lashed the region

The Northeast monsoon is wreaking havoc in Tamil Nadu.

The state saw normal life disrupted by the monsoon with schools and colleges being shuttered in nine Chennai districts.

The India Meteorological Department (IMD) announced the commencement of the monsoon on Saturday.

“Northeast monsoon rains commenced over coastal Tamil Nadu, Puducherry & Karaikal and adjoining areas of south Coastal Andhra Pradesh,” the IMD said in a release.

“Under the influence of setting in of northeasterly winds in the lower tropospheric levels over Bay of Bengal and South Peninsular India, the northeast monsoon rains commenced” over the said areas, it added.

But what do we know about the Northeast monsoon?

Let’s take a closer look:

What is it?

National Geographic defines the monsoon as a “seasonal change in the direction of the prevailing, or strongest, winds of a region”.

India’s climate is determined by the Southwest (summer) monsoon and the Northeast (winter) monsoon, as per MSN.

The Northeast monsoon, currently hitting Tamil Nadu, lasts between October and December.

According to Weather.com, it gets its name from the direction of the monsoon winds, which blow from the northeast to the southwest.

It is also referred to as the winter monsoon, retreating monsoon, or reverse monsoon (due to the reversal of wind direction as compared to the preceding southwest monsoon).

These winds take moisture from the Bay of Bengal and dump it over the southern states of Tamil Nadu, Andhra Pradesh, Kerala, and even south Telangana and Karnataka.

The northeasterly winds are also associated with the formation of cyclones from October to December — the peak cyclone season for the North Indian Ocean (covering the Bay of Bengal as well as the Arabian Sea).

The Northeast monsoon is far less powerful than the summer monsoons due to the Himalayas preventing much of the wind and moisture of the monsoons from reaching the coast, according to National Geographic.

Its normal onset date over India is 20 October, as per the website.

What is its impact on Tamil Nadu?

The monsoon comprises 11 per cent of the country’s rainfall, as per MSN.

However, Tamil Nadu receives around half its annual 914 mm rainfall during the Northeast monsoon, according to PTI.

As the southwest monsoon does for most of the country, the northeast monsoon affects agricultural activity in south peninsular India.

Seasonal rainfall has an impact on rice and maize productivity in Tamil Nadu and Andhra Pradesh.

As per Weather.com, the Northeast monsoon plays a key role in Tamil Nadu’s agricultural activities and reservoir management.

Chennai witnesses record rainfall

The record rains for Chennai and suburbs on Tuesday that began overnight, leading to inundation in a string of localities in city and on the outskirts, while two persons were killed in rain related incidents. For the first time in three decades, Nungambakkam, a core city area recorded 8 cm in a single day and suburban Red Hills 13 cm followed by 12 CM in Perambur, also in the city.

There was widespread rainfall in Tamil Nadu and showers ranged between 1 cm to 9 cm which includes Cauvery delta areas and coastal regions like Kanyakumari.

In view of the rains, two subways were closed here and the city witnessed traffic congestion and slow movement of vehicles. Chief Minister M K Stalin chaired a virtual meeting of top officials on monsoon preparedness and instructed officials to work in cohesion and directed them to take swift action on complaints. As regards Chennai city, 8 CM of heavy rainfall was recorded on November 1 at Nungambakkam and it is the first highest in the past 30 years and third such record in the last 72 years, Deputy Director General of Meteorology, Regional Meteorological Centre, S Balachandran told reporters.

In 1990, the city witnessed 13 CM rainfall and it was 11 CM in 1964, both on November 1. Several stretches near the arterial Anna Salai here, the congested parts of busy north Chennai, sleepy neighbourhoods tucked away in the southern and northern regions of the city and suburbs witnessed inundation. Similar was the scenario in several other parts of the State. While a man was electrocuted last night, a woman died after portions of a residential building collapsed in the city’s northern area of Pulianthope. A cow died of electrocuted in the suburb.

Water entered houses in low-lying areas in some parts of north Chennai. In at least 8 districts including Chennai, Kancheepuram, Tiruvallur and Chengelpet, a holiday was declared for schools. A weather bulletin said a cyclonic circulation lay over north Sri Lanka and its neighbourhood at lower levels and a “trough runs from this system to southeast Arabian sea.” Northeasterly winds continue to persist along and off North Tamil Nadu and adjoining coastal areas. Municipal Administration Minister K N Nehru said that 75 per cent of storm water drain work has been completed in Chennai Corporation areas.

Several areas that used to witness inundation in the past like the midtown GN Chetty Road have not seen waterlogging in view of drain improvement work, Nehru said. Minister for Hindu Religious and Charitable Endowments P K Sekar Babu also listed localities that had witnessed flooding during monsoon in previous years (during the AIADMK regime). He underlined that in view of implementation of upgradation and improvement of storm water drain work there was no water stagnation in flooding-prone localities.

Greater Chennai Corporation authorities inspected several areas and said that there was no rain water stagnation in localities like KK Nagar in view of preparatory measures and storm water drain work. Flood monitoring cameras have been installed by authorities in localities vulnerable to flooding. In view of the ongoing storm water drain improvement work and Chennai Metrorail phase-2 project, barricades have been put up in many stretches of roads.

While such infra-initiatives have already made traffic congestion the order of the day, the rains and waterlogging are the fresh woes people face during the monsoon. Balachandran said that from October 1 to November 1, Chennai District received 20 CM rainfall while the average for this period was 28 CM and it is 29 per cent less than normal. However, when the period between 1 to 31 October is considered, the city received 14 CM showers while the normal was 27 CM which was 48 per cent less than normal.

The current spell of rain, in a single day, has narrowed that gap by 18 per cent. For the next 3 days, most areas in Tamil Nadu Puducherry-Karaikal are expected to receive moderate rainfall, he said. During the next 24-hours, some places in Chennai, Kancheepuram, Tiruvallur, Chengelpet, and other northern districts including Vellore could witness heavy to very heavy downpour.

A couple of areas in districts falling under Cauvery delta zone, Ramanathapuram and Sivaganga may also witness heavy rainfall. Fishermen are advised to not venture into sea.

The Regional Meteorological Centre (RMC) in Chennai has forecast thunderstorms accompanied by lightning at isolated locations as well till 4 November.

With inputs from agencies

This article originally appeared on https://www.firstpost.com/ and was reproduced here with permission