The US-based Weather Company, an IBM Business, has said that India should prepare for a slightly earlier-than-normal onset (May 31) and above-normal rainfall (105 per cent) during the 2020 monsoon.

Uncalibrated climate model forecasts suggest an unusually wet monsoon season this year, although The Weather Company’s calibrated and bias-corrected model suggests a lower degree of dryness. India’s national forecaster, the India Meteorological Department (IMD), is expected to come out with the monsoon long-range forecast later this month.

Rain wave along West Coast

The Weather Company expects anomalous heavy rainfall threat for the West Coast. “Yes, we expect the West Coast to have the most anomalous rainfall this season, especially the South-West,” Todd Crawford, Chief Meteorologist at the US-based forecaster, told BusinessLine in an email interaction. Going by this, Kerala and Coastal Karnataka should brace for another busy season this year.

“We are expecting a transition from weak El Nino conditions towards La Nina conditions as we progress through the monsoon season, which will favour a large-scale atmospheric pattern that will become increasingly conducive to heavier rainfall later in the season,” the company’s seasonal forecast earlier made available exclusively to BusinessLine said.

Drier climes to North, East

However, the Indian Ocean Dipole (IOD) signal will likely not be as positive as last year; if it is positive at all, it may limit the chance of a repeat of the 110 per cent of the normal season that India experienced in 2019.

But the private forecaster said that the forecast should also factor in a multi-decadal dry signal (possibility for less-than-normal rainfall happening in decadal intervals), which also skews expectations a bit towards the drier side. The seasonal forecast shows dryness over most parts of North-West India, adjoining East India and North-East India as depicted in the graphic.

Trending towards La Nina

Responding to questions, Crawford said that The Weather Company’s forecast calls for drier-than-normal conditions across the North, with above-normal rainfall in other locations (see map). “This does not mean there will not be dry spells in other regions; just that we expect the season as a whole to be generally wet in most regions outside of the North. We expect it to be a rather wet monsoon season in most areas; parts of the North may be a bit dry as mentioned above.”

It is expected that a trend towards more La Nina type conditions will materialise as the monsoon season progresses, which should favour heavier rainfall later in the season across all areas. “Unlike last year, we do not expect a very strong IOD; so it may be difficult to get back to the 110 per cent levels that we saw last year.”

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