Monsoon Forecast 2023: IMD Vs Skymet

The southwest monsoon remains a key lever for determining India's growth prospects over the ongoing fiscal year. The India Meteorological Department, the official agency responsible for weather forecasting, predicts a 'normal' monsoon in 2023, bringing cheer to farmers and markets. But there is a catch. Some other weather watchers and private agencies such as the Skymet expect the monsoons could underperform as El Nino is likely to set in over the second half of the monsoon season.

Here are the key differences between the two forecasts:

• IMD: Quantitatively, the southwest over the country as a whole is likely to be 96% of the long period average, with a model error of ± 5%. Rainfall ranging from 96-104% of the LPA is classified as 'normal.' The LPA of the monsoon season rainfall over the country as a whole for the period 1971-2020 is 87 cm.

• Skymet: It expects the upcoming monsoon to be 'below normal' to the tune of 94% with an error margin of +/-5% of the long period average of 868.6 mm for the four-month period from June to September. The spread of below-normal being 90-95% of LPA, the same as IMD's. Skymet expects the monsoon to be 99% of LPA in June, 95% of LPA in July, 92% of LPA in August and 90% of LPA in September.

• The IMD's strategy uses both dynamical and statistical forecasting system. Multi-Model Ensemble (MME) forecasting system based on coupled global climate models (CGCMs) from different global climate prediction centres, including IMD’s Monsoon Mission Climate Forecast System (MMCFS) is used in dynamical forecast system.

• Skymet runs its own numerical weather models and provides an array of weather-based services through data and information tools. 

The probability forecasts by category for the seasonal rains over the country by the IMD, suggest higher probability for monsoon seasonal rainfall to be normal.

According to Skymet, Monsoon probabilities for the season are:

• 0% chance of excess (seasonal rainfall that is more than 110% of LPA)

• 15% chance of above normal (seasonal rainfall that is between 105 to 110% of LPA)

• 25% chance of normal (seasonal rainfall that is between 96 to 104% of LPA)

• 40% chance of below normal (seasonal rainfall that is between 90 to 95% of LPA)

• 20% chance of drought (seasonal rainfall that is less than 90% of LPA)

• According to the IMD's forecast, La Nina conditions have changed to Neutral conditions over the equatorial Pacific region. The latest model forecasts indicate that El Niño conditions are likely to develop during the monsoon season.

That said, "all El Niño years are not bad monsoon years", the IMD said at a media briefing for forecasting the southwest monsoon rainfall.

• Key oceanic and atmospheric variables are consistent with ENSO-neutral conditions, according to Skymet. Likelihood of El Niño is increasing and its probability to become a dominant category during the monsoon is growing large. 

El Nino return may presage a weaker monsoon, according to Skymet.

The term El Niño refers to a warming of the ocean surface, or above-average sea surface temperatures, in the central and eastern tropical Pacific Ocean. 

IMD: At present, neutral Indian Ocean dipole conditions are present over the Indian Ocean and the latest Climate models forecast indicates that the positive IOD conditions are likely to develop during the south west monsoon.

Skymet: Indian Ocean Dipole has the potential to steer monsoon and negate the ill effects of El Nino, when sufficiently strong. IOD is neutral now and is leaning to turn moderately positive at the start of monsoon, according to Skymet.

The Indian Ocean Dipole is defined by the difference in sea surface temperature between two areas or poles—in the western and eastern Indian Ocean. The IOD affects climate and is a significant contributor to rainfall variability in the region.

IMD: The spatial distribution suggests normal to above normal rainfall likely over many areas of Peninsular India and adjoining East Central India, Northeast India and over some parts of Northwest India, according to IMD. Normal to below normal rainfall is likely over some areas of Northwest India and parts of West central India and some pockets of Northeast India.

Skymet: In terms of geographical prospects, Skymet expects northern and central parts of the country to be at risk of being rain deficit. Gujarat, Madhya Pradesh and Maharashtra will witness inadequate rains during the core monsoon months of July and August. Punjab, Haryana, Rajasthan and Uttar Pradesh , the agri bowl of North India, are likely to observe  less than normal rains during the second half of the season.  

A good monsoon at the start of the season may facilitate early kharif sowing while comfortable reservoir levels- 21% above 10-year average for the country, may help India tide over a progressively waning monsoon, stated a research note by Teresa John, economist at Nirmal Bang Institutional Equities.

 Both the forecasts point towards deficient rainfall, but the extent of deficiency is not as bad as was previously expected considering the El-Nino conditions, said Mitul Shah, head of research at Reliance Securities. The impact on agriculture as always would depend on the spatial and temporal distribution of rainfall over the season, he said.

Over the last few years, crop damage has occurred largely due to improper distribution of rainfall like late onset delaying sowing or less rainfall during the growth stage leading to lower yield. Late withdrawal of monsoon has also impacted the standing crop in the last few seasons. Shift towards less water intensive crops as well as irrigation would help mitigate the impact from deficient rainfall in the second half, Shah said.

"Our main concerns would be around Uttar Pradesh, which is expected to experience ‘below normal’ rainfall, with the state’s reservoirs also 10% below the 10-year average," said John. However, the risk of El Nino would be potentially negated by a positive IOD even in the latter half of the monsoon season, she added.