Only ghosts in horror films can be as unpredictable as rains in Kerala.
You expect them at a particular moment and they appear in all fury at the most unexpected time. Next time, mocking your anticipation, they startle you when you had just dropped your guard.
Since 2018, the year of the deluge, rains have behaved in the eeriest manner. That year, though the usual southwest monsoon months of June and July got normal rainfall, Kerala received its highest deluge-inducing showers in August. In 2019, the rains bunked June and July but made a frightening appearance in August.
The first COVID year, 2020, saw its highest rainfall not in August but in September. And this year, just when it was felt Kerala had entered the largely safe northeast monsoon phase, it burst upon Kerala in the middle of October like a ghost in a full shriek.
2021 October drowns 1999 record
This October, Kerala has received the highest rainfall recorded for the month in history (at least since 1901, the year India started documenting rainfall data). It received 589.9 millimetres of rain, more than the previous high of 566 mm recorded in October 1999.
All districts in Kerala, except Alappuzha, had received “large excess” rainfall in October. Large excess is defined as rainfall that is 60% above normal. Palakkad and Pathanamthitta, too, set new October records. If the former record for Palakkad was 446 mm of rain in October 1999, this time it was 575.2 mm. Pathanamthitta's old record was 792 mm in October 1999. This October, the district received 866.9 mm.
The severity of the showers was so scary that in October alone Kerala received nearly 100 mm more rain than what is expected for the 92-day northeast monsoon season from October 1 to December 31. The normal rainfall expected during the three months is 491.66 mm. By the end of October itself, Kerala was pounded by 589.9 mm of rainfall.
Multiplicity of cyclonic systems
The low-pressure formations over the Bay of Bengal in the east and the Arabian Sea on the west are said to be the cause for the vicious intensity of the October rains.
In October, there were five such cyclonic formations, both in the Arabian sea and the Bay of Bengal. One of them, low pressure over the Arabian Sea, had caused the devastating rains of October 16 that ravaged Kootikkal ad Kokkayar in Kottayam and Idukki.
Both the Arabian Sea and the Bay of Bengal have become warmer, triggering cyclonic systems. Rajeevan K, the meteorologist at Kerala State Emergency Operations Centre, said the Bay of Bengal was more prone because of the negative condition of the Indian Ocean dipole.
When this condition exists, the surface temperature over the Arabian Sea would be relatively lower than that over the Bay of Bengal. "A cyclonic formation that formed over the southeast Bay of Bengal has now moved to the Lakshadweep area," Rajeevan said.
Madden-Julian's provocation
However, Rajeevan said that it was usual for cyclone systems to form during the northeast monsoon season. The post-'southwest monsoon' season is also known as the cyclone season. "But it is the presence of an atmospheric system called Madden Julian Oscillation (MJO) that makes these cyclones potentially dangerous," Rajeevan said.
The MJO is the eastward progression of a band of clouds over the equator in specific time intervals. Its presence over India can enhance the potency of the cyclonic systems that are formed over the Bay of Bengal and the Arabian Sea.
No let-up in November
The IMD has therefore predicted heavy rains in November, too. Usually, Kerala expects 150 mm of rain in November. But by November 3 itself, Kerala has received 70 mm, nearly half the expected rains this month.
In fact, the monsoon behaviour in 2021 was highly erratic. Kerala had record rains in January, May and October, periods when rainfall activity is relatively weak, but suffered from a deficit during the monsoon months of June and July. Between June 1 and September 30, there was a rainfall deficit of 16% in Kerala.
And then in October, the clouds turned terrifyingly black.
