In today's Finshots we see all the debate surrounding monsoon predictions

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The Story

Monsoons mark the arrival of the most spectacular rains in India. It also marks the beginning of the sowing season in many parts of the country. Kharif crops are usually grown at the beginning of the first rains and then harvested at the end of the monsoon season. And as such, monsoons bring with them joy and misery in equal parts. Too much rain and everything goes for a toss. Too little rain and there’s sorrow all around. Early monsoons can leave you scampering at times. Delayed monsoons can also gravely affect livelihoods. This is why we have the IMD (The India Meteorological Department) making formal predictions about monsoon and other weather events. They help farmers and civilians better prepare for what’s coming. And needless to say, there’s a lot leaning on their predictions.

But they don’t always get it right. For instance, consider this year’s predictions, made specifically for Kerala. IMD was expecting the monsoons to arrive early on May 27. And based on historical trends, this would have been the quickest in five years. Even Skymet — a private weather forecasting company had predicted monsoons to arrive early—on May 26th actually. But then, the monsoons never arrived. In fact, it would take another two days for the IMD to formally declare the onset of Monsoon in Kerala. And while in the grand scheme of things, 2 days might not seem massive, it is significant. Especially considering IMD’s predictions were all over the place during this last month. As one article in the Hindustan Times notes — “Experts did not take too kindly to IMD’s decision, which, strangely, came only two days after the body suggested the onset of the monsoon over Kerala would be delayed — this, a few weeks after claiming the onset would be early. Yes — there was a flip, then a flop, then a flip again.”

But, that isn’t where the controversy ends.

See, predicting the monsoon is one thing. But declaring the onset of monsoon is a less subjective enterprise. For instance, if after May 10, a certain set of stations receive rainfall of 2.5 mm or more for two consecutive days, then the IMD can formally announce the onset of monsoons if the wind patterns and the clouds exhibit certain traits as well. This is a well-defined standard — a standard set by the IMD itself. And so when they announced the early onset of monsoon you’d have expected these conditions to be met. However, it seems many stations did not receive the mandated 2.5 mm rainfall on the second consecutive day, leaving their declaration open to scrutiny. And experts have been scrutinizing this assessment.

So we have to ask — “What’s happening here? Is IMD losing its touch or is something amiss?”

Let’s start with the relevance first. How important are these predictions and assessments in real life?

Well, fairly important it seems. The agriculture sector accounts for nearly 14% of the economy and employs half of India’s working population. So if you have faulty weather predictions, these people suffer greatly. For instance, if monsoons arrive early compared to IMD forecasts, farmers may delay sowing their crops. This ultimately leads to low crop yields and affects the total output. There’s an added impact on farm income and consumer expenditure. Inflation becomes a real concern very quickly which in turn could spur the RBI to adjust interest rates. It’s a domino effect. So clearly, there’s a lot riding on the predictions.

However that being said, you have to cut forecasters some slack. Predicting weather events (and monsoons) is an extremely tumultuous affair even with the advances in science and technology. Consider this — Until 2016, IMD had relied on statistical methods i.e. They made forecasts using correlation. They’d look at historical relationships between monsoons and certain weather events and try and guess the future. But then, they switched it up. They began running simulations using massive supercomputers. Using this technique they’re effectively trying to measure the current state of variables that affect weather (say temperature, humidity etc) and then try and simulate what’s likely to happen sometime in the future based on our current understanding of physics. This is a more time-consuming (and expensive) affair but one that’s more reliable. In fact, IMD has got two monsoon forecasts right in the past decade — once in 2011 and in 2017. And Skymet with 6,500 observation centres has accurately predicted the monsoon on six occasions (from 2011 to 2019).

But predictions can quickly go awry when you’re talking about chaotic systems. Systems where a mishmash of variables can deeply affect future outcomes. A flap of a butterfly could trigger a tornado. And a small change in temperature could delay the monsoons. No man-made computer model can account for all these variations and so the predictions will always have a margin of error.

However, this margin dissipates over time. If you’re making predictions about the monsoon in April, you’re likely going to get it wrong. However if you’re doing it at the fag end of May, you’ll have a better chance of acing it. For instance, a seven-day forecast can accurately predict the weather about 80% of the time, while a five-day forecast can accurately predict the weather approximately 90% of the time. So you can’t blame IMD entirely for getting it wrong sometimes. They have a tough job at hand.

However what about the declaration of monsoons? Surely, that isn’t dependent on supercomputer simulations no? How come they bungled things there?

Well, one explanation is that the IMD made the hasty declaration “since it had committed itself saying the monsoon would set in on May 27.”

And by May 29, they were already 2 days late. So perhaps they called it early hoping to stay close to their original predictions. But IMD contests otherwise. Their argument is that they looked at certain important metrics and made an assessment based on their best judgment. Only problem? The rains in Kerala have been weak, making the declaration look dubious.

Very dubious in fact.

So yeah, that’s kind of the controversy here. You would think that these would be fairly trivial events with little scope for confusion. But the reality is monsoons are far from trivial.

Anything, but trivial.

Until next time…

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