‘Monsoon has a way of its own, can beat the best models at any given time’

The Indian monsoon has got a way of its own that manifests in the most unpredictable way it has behaved from time to time. It continues to beat the best predictions made by the choicest of models, forcing the protagonists to go back to the drawing board, hoping for the best next time.

The almost-mythical June-1 timeline for its onset gets breached with impunity since the movement of the parent Inter-Tropical Convergence Zone (ITCZ, or the equatorial band of low-pressure area moving into the Northern Hemisphere along with the sun) and associated cloud formation defy predictions.

Sheer unpredictability

The sheer unpredictability that clouds it seems to have endured a lot more than the monsoon itself, which continues to be among the most researched climatic phenomenon. Barely understood in the best of times, it is complicated further by climate change, says The Economist. Why is this so?

For one, numerous physical forcings are interacting on a monsoon simultaneously (not just the El Nino-La Nina or the Indian Ocean Dipole), but their linear/non-linear impact on the system has been mostly cyclic. These are not yet fully understood nor assimilated in predictive monsoon models.

Plays to own dynamics

The monsoon also chooses to play in its dynamics, notes GP Sharma, President, Meteorology and Climate Change at Skymet Weather, leading private forecaster, which came out with an outlook for a ‘healthy normal monsoon’ this year assessed at 103 per cent of the long-period average.

“For instance, we have given a forecast for all four monsoon months. This is what our predictions are. Invariably, it need not turn out exactly as per the script. The monsoon shouldn’t oblige us and behave in all the four months, nor should it fail us irrespective of a La Nina or El Nino,” Sharma told BusinessLine .

But if it behaves the way we forecast now, it will mean it will act in all four months, he explained. The last time when it behaved in all months was in 2007. All four (June, July, August and September) were good. Or take 1975 or 1956 when all these were on the positive side of 100 per cent.

The case of exceptional 1997

Sharma singled out the exceptional 1997 when, despite a strong El Nino, the monsoon had beat all conventions and emerged above normal. El Nino is usually known monsoon killer. “Surprisingly, all four months were good…the lowest was in the core July month which was at 95 per cent of the long-period average that year.”

“I still consider it okay in an El Nino year,” says Sharma. July is the rainiest of all four monsoon months and very crucial to the farm economy. But 95 per cent in July in an El Nino year is just as good. All the rest three months in 1997 were plus-100 per cent, Sharma said.

Good monsoons on a trot

“We have had three years of good monsoon on a trot but not all three above normal. 1996, 1997, 1998 were all normal within 101 to 103 per cent. Before that, we had 1986, 1987 and 1988, with one being above normal. But we haven’t had all three years statistically above normal for three years in a row. We should wait to see if this happens when the 2021 monsoon runs its course.”

Pointing to the expected good June forecast this year, he said that it is significant when seen against the record in the recent past. But whatever the strength of the monsoon, the rains enter North India only by June-end. So, it is mostly the other parts of the country that benefit from a good June, Sharma said.

Significance of June rains

Good June rainfall is best for country’s central parts and a good signal for Kharif sowing. But the northern parts of the country do not directly benefit here. Punjab, Haryana, West Uttar Pradesh and the rest of the northern farm belt do not wait for the rains since they are well-irrigated otherwise.

Asked about the projected shortfall in North Interior Karnataka, Sharma said that any good monsoon leaves 10-15 per cent of the total area with a shortfall. It is only North Interior Karnataka’s turn now (apart from North-East India, which seems to be a ‘perpetual deficit case' though for different reasons).

Difficult to decode

“We do not have any clue as to which area might come under the shortfall area since no two monsoons are the same. Nor for that matter does an El Nino strike a specific pocket twice. The pattern keeps shifting, and decoding that is very difficult. But this is what the model projects for that part of Karnataka this year,” Sharma said.

One thing worth mention here is that North Interior and adjoining Coastal Karnataka have huge rainfall normals. Places such as Karwar and Mangaluru have more than 1,000 mm of annual rainfall. “So, any deviation will be projected as deficient although it may not make as big an impact on the ground as on statistics.”

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