Chennai’s joy ride on a wave of easterlies may end; temperatures to flare up

Vinson Kurian Thiruvananthapuram | Updated on April 15, 2020 Published on April 15, 2020

Chennai might just have been enjoying a benign spring and an early summer this year, but all good things have to come to an end sooner than later. Especially when they relate to the Elements.

It turns out that the southern metropolis has been riding a wave of unusually strong and comforting easterly winds in the lower levels of the atmosphere, resulting in stronger-than-normal sea breeze.

Extended easterly bursts


The land heats up more quickly than the sea because the former absorbs heat faster than water. Hence, air over the land surface becomes more heated than air above the sea.

The hot air over the land being lighter, moves up, to be replaced by cooler air from the sea. Thus, a cool breeze carrying moisture blows from the sea to the land. This is what constitutes the sea breeze.

DS Pai, Head, Climate Research and Services, India Meteorological Department, Pune, told BusinessLine that the easterly burst has ensured that maximum temperatures in Chennai remain close to normal while the minimum (night) temperatures are slightly below normal.

According to S Balachandran, Deputy Director-General, IMD, Chennai, the current weather in Chennai is normal. The departure in maximum temperature is at best 1-2°C from normal.

Thunderstorms on the horizon

Pai told BusinessLine that in the next three to four days, the easterlies will weaken and the maximum temperature will start rising. “Higher temperatures will trigger formation of some convective (rain-bearing) clouds,” he added.

Convection is simply the process of warmer air rising since it is less dense than the surrounding atmosphere. The more convective energy available, the higher the cloud will reach into the skies.

If convective clouds reach above 6 km height, it is called deep convection. If they do not reach as high, it is called shallow convection. Only deep convection produces strong rain showers and thunderstorms.

According to private forecaster Skymet Weather, February and March are the least rainy months for Chennai with average rainfall of 3.4 mm and 3.5 mm, respectively. Day temperature is the main trigger actor for weather activity during this phase. Presence of moisture in the atmosphere and rise in temperatures set up convective clouds, rain and thundershowers during the latter part of the day.

No lockdown impact

Thomas Prasad, leading city-based data analyst and a weather aficionado, says the next couple of weeks could see the city transitioning into the summer, with temperatures escalating. A summer-time weather system (low-pressure area) cannot be ruled out in the Bay of Bengal along the Tamil Nadu coast, followed by the usual refreshing thunderstorm season.

Meanwhile, has the lockdown and restrictions on industrial activity, steep dip in power and oil consumption and the generally clean air had any impact on the pre-monsoon thunderstorm season?

Mrutyunjay Mohapatra, Director-General, IMD, says there has been normal thunderstorm activity in the country so far. “To my knowledge, there has been no such experiment that has probed the impact of the lockdown on thunderstorm activity worldwide,” he informed BusinessLine.

Less aerosol concentration

The meteorological factors leading to thunderstorm are intense heating, moisture availability in lower levels, instability in the atmosphere, and triggering mechanism such as troughs, cyclonic circulations, low-pressure areas.

Mohapatra agreed that the lockdown has resulted in reduction in aerosol concentration in the atmosphere, which may have a bearing on the concentration of hygroscopic nuclei needed for rainfall. “However, what could be the quantitative contribution cannot be told without research and experiment.”

Pai says: “I don’t think there is any lockdown impact on the dynamics of the weather. Yes, there is an impact on air quality for temporarily. The lockdown also might have reduced emissions of greenhouse gases. But it’s impact on weather will be felt after several years, and only if lockdown-type situation persists for many years.”

Lower April temperatures

Leading Chennai-based weather blogger K Srikanth of @ChennaiRains (COMK) says the city has seen lower temperatures in April, during 2005, 2007 and 2008 (see table). The numbers pertain to Chennai airport, which tends to be warmer during the day and cooler compared to the city observatory. Airport data come in handy because of long-term availability, Srikanth told BusinessLine.

In fact, he had written in a blog as early as on March 31 that many people have started to wonder if the lockdown could play any role in modulating weather particularly from the perspective of influencing the ‘urban heat island’ effect due to reduced vehicle traffic and pollution.

One of the earlier studies which COMK did had indicated that the winters are getting warmer in Chennai and it may not present an accurate picture of whether the lockdown is influencing the weather pattern.

Published on April 15, 2020

A letter from the Editor

Dear Readers,

The coronavirus crisis has changed the world completely in the last few months. All of us have been locked into our homes, economic activity has come to a near standstill. Everyone has been impacted.

Including your favourite business and financial newspaper. Our printing and distribution chains have been severely disrupted across the country, leaving readers without access to newspapers. Newspaper delivery agents have also been unable to service their customers because of multiple restrictions.

In these difficult times, we, at BusinessLine have been working continuously every day so that you are informed about all the developments – whether on the pandemic, on policy responses, or the impact on the world of business and finance. Our team has been working round the clock to keep track of developments so that you – the reader – gets accurate information and actionable insights so that you can protect your jobs, businesses, finances and investments.

We are trying our best to ensure the newspaper reaches your hands every day. We have also ensured that even if your paper is not delivered, you can access BusinessLine in the e-paper format – just as it appears in print. Our website and apps too, are updated every minute, so that you can access the information you want anywhere, anytime.

But all this comes at a heavy cost. As you are aware, the lockdowns have wiped out almost all our entire revenue stream. Sustaining our quality journalism has become extremely challenging. That we have managed so far is thanks to your support. I thank all our subscribers – print and digital – for your support.

I appeal to all or readers to help us navigate these challenging times and help sustain one of the truly independent and credible voices in the world of Indian journalism. Doing so is easy. You can help us enormously simply by subscribing to our digital or e-paper editions. We offer several affordable subscription plans for our website, which includes Portfolio, our investment advisory section that offers rich investment advice from our highly qualified, in-house Research Bureau, the only such team in the Indian newspaper industry.

A little help from you can make a huge difference to the cause of quality journalism!

Support Quality Journalism
This article is closed for comments.
Please Email the Editor
You have read 1 out of 3 free articles for this week. For full access, please subscribe and get unlimited access to all sections.