The delayed intense spell in September helped Kerala reduce the southwest monsoon rainfall deficit significantly, much to the delight of the State which was staring at a drought-like condition until recently. However, the four-month season draws to a close with 34% deficient rains, third largest monsoondeficient year in the 123 years of recorded weather history of the Kerala, whereas the monsoon over the country as a whole was normal with the country receiving 94% of the long period average (LPA).
The State received 1326.1 mm rainfall till September 30 this year against the LPA of 2018.6 mm. This is the 15th deficient southwest monsoon for the State in over a century. The highest deficient monsoon in recorded history was in 1918 with 1104.3 mm of rains, followed by 1297 mm of rain in 1976. In 2016, the year when the State witnessed one of the worst droughts in recent history, the State received 1353.3 mm rainfall. The extremely low monthly rainfall in August coupled with the weak onset in June has aggravated the situation in Kerala.
Cyclonic storm Biparjoy, formed in the Arabian Sea in the first week of June and spent around eight days in the sea before making landfall in northwestern India and southern Pakistan on June 15, had upset the monsoon pattern over Kerala, leaving a 60% deficient rain in the opening month. Though July witnessed relatively normal rainfall, August witnessed extremely low rainfall with a drop of 87% monthly rain due to the adverse effect of El Niño over the equatorial Pacific region.
Meanwhile, the approaching northeast monsoon holds promise for Kerala with a positive Indian Ocean Dipole (IOD) under way, identified by above normal sea surface temperature over the Arabian Sea. The IOD index is +1.45 °C for the week ending 24 September. This is its sixth week above the positive IOD threshold (+0.40 °C), according to Bureau of Meteorology, Australia. When a positive IOD and El Niño occur together, the drying effect of El Niño will be weaker along the west coast of India. The long-range forecast issued by the India Meteorological Department (IMD) also forecasts above normal rainfall for Kerala during the northeast monsoon period including October.
Low storage
Considering the precarious storage levels in the reservoirs under the Kerala State Electricity Board (KSEB), the State desperately requires above normal precipitation in October. Despite the late surge, Idukki reservoir which accounts for the bulk of hydel power production in the State has a storage of 37% as of September 30, against 79% during the same period last year. Pamba and Idamalayar, two other major reservoirs, have a storage of 54 and 53% water, respectively, against the previous storage of 76 and 86%, respectively, last year.
