“The rainfall in September has been quite good, the country as whole received 9% above the normal benchmark (long period average) rainfall so far,” Mohapatra said.
After scanty monsoon rains in August which was also the lowest since 1901, rainfall this month has been surplus, erasing the deficiency to an extent. India Meteorological Department (IMD) in May predicted normal rainfall during June-September period despite strong possibility of development of El nino during the season. Mrutyunjay Mohapatra, Director General, IMD spoke to Sandip Das explaining how the initial forecast of normal rainfall would hold good despite fluctuations in rains across months.
Q: How do you assess monsoon performance this season so far?
The rainfall in September has been quite good, the country as whole received 9% above the normal benchmark (long period average) rainfall so far. It has compensated for the large deficiency in the rainfall in August to a large extent. This season started with deficient June and followed with surplus rainfall in July and then a hugely deficient August. If we look at September rains, it is contributed by positive Indian Ocean Dipole (IOD) which essentially give a boost to rains, even if El Nino has become strong this month. It clearly indicates what we had shared in the beginning of the season, El nino is not the only factor which influences rains during monsoon months (June-September).
Q: What are the factors which impacted the monsoon rains this month?
It is because of a phenomenon called Madden Julian oscillation (MJO), which causes intra-seasonal variability in the tropical atmosphere and positively influences the monsoon performance. MJO amplifies the monsoon clouds and helps in rainfall. In July, the atmosphere was not responding to the development of El Nino while in August the atmosphere responded to El Nino. This was not countered by MJO, thus there was a huge deficiency in the rainfall in August. There are many large scale factors which influence Indian monsoon. One of them is El nino besides IOD and Euro-Asia sown cover which was less this year thus favourable to the monsoon.
Q: What are the areas which would have deficient monsoon rains and prospects of rainfall till end of this month?
In the rest of the current month, we expect good rainfall mainly in the central and southern regions. Deficiency is higher over paddy growing eastern parts of the country – eastern Uttar Pradesh, Bihar, Gangetic West Bengal and Jharkhand. The paddy dependent area of the eastern region, rainfall has been less and it was around 50% less against the benchmark – long period average till the end of July. In August-September this area received rains. and now the deficiency in these areas have been reduced to 20% of the normal benchmark. We had anticipated below normal for August, but it is difficult to predict extreme weather conditions like scanty rainfall in August.
Q: IMD had predicted normal rainfall for the season at 96% of benchmark. What is your current assessment?
Overall rainfall in June-September period will end up as predicted at 96% of benchmark with error % of +/- 4%. We are sticking to the May forecast of a normal monsoon and It’s not a deficient year. Whatever apprehension was there in the beginning of the season like drought year as El Nino is coming, has been put to rest. Currently there are moderate El Nino conditions prevailing. Another aspect of the monsoon is the El Nino favours north-eastern monsoon rains (October-December), which covers Tamil Nadu, southern Karnataka, Rayalaseema and Kerala.
Source:financialexpress.com