At the beginning of this package, two questions were placed on the table, deliberately, as the only two questions this whole cover story exists to answer. Here they are again, verbatim. One: how does a monsoon system this vast — an engine of wind and water that has run every summer for longer than any human institution has existed — fall short by a tenth? Two: how do we know in April what the sky intends to do in September?
By this point in the package, the reader has walked the entire machine: the Nairuti and Ishanya systems, the atmospheric engine room, the Kerala onset, the mausim mariners and Halley and Walker, India’s place among the world’s monsoons, and the flood-and-drought paradox this same shortfall produces on the ground. It is time to try the answers.
How Does It Fall Short?
Not through any kind of mechanical breakdown — through being remotely jammed from seven thousand kilometres away. A warming Pacific slid the Walker circulation’s rising chimney eastward and pressed a lid of sinking, moisture-starved air directly over the Indian subcontinent; the Somali jet, the season’s main fuel line, ran weaker than normal as a result; and the Indian Ocean’s own internal counterweight, the Dipole — the very mechanism that rescued the monsoon from an equally strong El Niño in 1997 — sat neutral this year and offered no rescue at all.
And How Do We Know in April?
Strictly speaking, we don’t — not in the sense of a prophecy. What is actually known in April is the measured state of the ocean, and unlike the sky above it, the ocean carries a memory that runs seasons deep. Feed that measured ocean warmth into coupled models of sea and atmosphere together, run dozens of the world’s best such models as an ensemble rather than trusting any single one, and what emerges is not a certainty but a calibrated probability: this season will most likely run short, and by roughly a tenth. When the underlying ocean state shifts, as it did visibly between April and May this year, the forecast shifts with it, transparently, in public. That revision is not the forecasting system failing. It is, quite precisely, the forecasting system doing exactly what it is designed to do.
Earning the ability to say even that much took a century and a half of genuinely hard-won science. Gilbert Walker’s early-twentieth-century statistical correlations frayed badly after his own time; from 1932 to 1988, IMD actually withdrew from issuing all-India seasonal forecasts altogether — a half-century of institutional humility that rarely makes it into the popular history of Indian meteorology. The decisive shift from statistics back to physics came only in 2012, when the government’s Monsoon Mission tasked the Indian Institute of Tropical Meteorology in Pune with building a genuinely dynamical prediction system from first principles; it went operational in 2017, and since 2021 its output has run inside a Multi-Model Ensemble alongside the world’s other leading forecasting centres — many models voting together, precisely so that no single model’s blind spot gets to decide the season’s headline number alone. Feeding all of this is a planetary-scale observing infrastructure that barely existed a generation ago: the INSAT-3DS satellite, whose data lands at IMD’s own Earth Station in Hyderabad; a national Doppler radar network that has grown from fourteen installations a decade ago to roughly fifty today; and machine-learning systems now running alongside the traditional physics-based models on multiple timescales at once.
Asked to characterise just how difficult this entire enterprise remains, even with every one of those tools in hand, Prof. K. Ashok reached for an image sharper than anything in the technical literature:
“Imagine I give you a bag of ten thousand coins, and someone quietly removes 9,999 of them — you would notice immediately. But if I remove just a single coin from the bag, you likely wouldn’t notice. That’s the challenge of tropical weather prediction.” — Prof. K. Ashok, University of Hyderabad
The mid-latitudes, in other words, are forecast by watching a handful of dominant, slow-moving systems that announce themselves clearly. The tropics, and the Indian monsoon above all, are forecast by trying to notice the one coin missing from a very large bag — which is precisely why the same establishment capable of calling the season’s overall shortfall correctly, months in advance, can still miss an onset date by a week, and why Prof. Ashok considers that particular miss a genuine success rather than a failure, as established earlier in this package.
The audit that decides who was right is not abstract or distant. On 30 September, the season closes its books, and the 90 per cent call this package has followed since its opening page meets the rain gauge directly. Worth remembering, as that date approaches: the famine of 1876–78 that first forced India to build this entire scientific apparatus was itself driven by an El Niño — by reconstructed estimate, the strongest on record, and the very same phenomenon now swelling again in the Pacific a hundred and fifty years later. A century and a half ago, that event arrived in India as an ambush, killing on a scale still argued over by historians. This year, it arrived as a forecast, tracked publicly from April onward, revised in the open in May, and now awaiting its final audit in September. That gap — between ambush and forecast — is what a century and a half of science actually bought. This package has just spent it, alongside you.
– Ravindranath P
