Kerala nets 13% less SW monsoon rainfall, braces for above-normal northeast monsoon

Although the four-month southwest monsoon season drew to a close on a positive note with the country registering above-normal rainfall (108% of the long-period average), Kerala witnessed a shortfall of 13% in rainfall during the season.

This year the month-wise spatial distribution of rain in Kerala was in tune with the pattern of the long-period average with June and July recording the bulk of the southwest monsoon rain, followed by a gradual reduction in rainfall activity in August and September.

Similarly, the number of extreme and very heavy rainfall events was relatively less this year, with Kerala witnessing only three days of extremely heavy rainfall events (more than 21 cm in 24 hours), 16 days of very heavy rainfall (11–20 cm in 24 hours), and 37 days of heavy rainfall (7–11 cm in 24 hours).

For instance, the extreme rainfall events were 33 in 2018 followed by 163 very heavy rainfall and 607 heavy rainfall events during the flood year. There has been a gradual reduction in extreme weather events in Kerala since 2020.

Now, the State is hoping that the shortfall in southwest monsoon will be offset by above-normal rainfall in the northeast monsoon period, which begins by the middle of October and lasts till the end of December.

The long-range forecast issued by the India Meteorological Department (IMD) warns of excess precipitation in Kerala during the northeast monsoon period.

Although the withdrawal of the monsoon from northwest India was three days ahead of the normal withdrawal date and just on time in many States so far, the withdrawal is likely to be delayed in the next few days with two systems prevailing in the Bay of Bengal and the Arabian Sea.

The upcoming system in the Bay of Bengal is likely to intensify into a depression and cross the south Odisha and north Andhra Pradesh coast by October 3. The system will not have a major impact on the weather in Kerala.

However, this is likely to have a bearing on the onset of the northeast monsoon. As per the long-period average (1901-2021), the northeast monsoon will have to set in over Kerala on October 19 with a standard deviation of eight days. It means an onset between October 11 and 27 is considered normal onset.