Models are showing there is a persistent signal in favour of a normal monsoon this year that seems to be amplifying as the season progresses. Today’s models correctly project the departure from normal, but not the quantum. There is a high chance that the monsoon will be between 104% and 110% of the long-period average. The long-period average is 89 cm for June, July, August and September over the last 130 years. There is a 10% chance of an excess monsoon, but least chances of a drought.
This monsoon will most probably be like the one in 2013. Monsoon in that year was 106% of the average. The confidence level of this forecast is 80%. Although monthly scales are hard to predict, models indicate cumulative rainfall for July and August will be between 105% and 110% of their respective monthly averages. This is so because July and August are the months to receive the bulk of monsoon rain followed by September when the monsoon sets to withdraw.
In such a scenario, we can speculate that extended monsoon dry spells for more than five days in a row might be few. Skymet’s models and research suggest that monsoon in central India will be above normal 105-110%. Rainfall in south and east and north-east India, too, will be normal. Probability of a normal monsoon in north-west India is relatively less than central and south India, but much higher than in 2014. Punjab, Haryana and Uttar Pradesh had severe rainfall deficits last year.
The El Niño Southern Oscillation refers to a phenomenon where the water off the coast of Peru is either neutral, cool or warm. Warm El Niño correlates well with a drought in India and cool La Niña correlates with surplus rainfall. Such a signal is also favourable. After the El Niño of 2014, which caused a drought last year, equatorial Pacific will revert to near-neutral conditions. When this happens, there is statistically an 80% chance of a normal monsoon. In the last 130 years, there have only been four back-to-back droughts. If we put all the data together, there is only a 3% chance of a drought in 2015.
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