​ Tamil Nadu chief minister MK Stalin on Tuesday said the India Meteorological Department (IMD) failed to issue timely warnings about the extreme rainfall that battered four southern districts in the state between Saturday and Monday and added that the agency issued a red alert two days after the downpour began.

The Chennai regional meteorological centre (RMC) issue a warning about the rainfall on December 17, by which time large parts of Tamil Nadu had gone underwater as record showers lashed the state’s southern districts.

Read here: Proper measures for rescue and relief operation carried out despite late warning: CM Stalin

“It rained several times higher than what was forecast by the meteorological centre. It was unprecedented,” Stalin told reporters in Delhi.

IMD’s inability to accurately predict the showers and their crippling after-effects on a state that was already contending with the impact of Cyclone Michaung have called into question the weather department’s methods and processes.

Four southern districts in Tamil Nadu — Thoothukudi, Tirunelveli, Tenkasi and Kanniyakumari — were engulfed by ceaseless rain on December 17 and 18, which was the region’s wettest spell since 1871, said Stalin.

The weather office issued a red alert on Saturday evening for rainfall above 21cm, but Kayalpattinam in Thoothukudi district alone received 95 cm rainfall on that day, showed IMD data. In fact, Kayalpattinam received more rain in a day than the 70cm the entire district receives on average in a year, according to the data.

“Though we received the warning from the meteorology department a bit late, and though it rained more than what was forecast, Tamil Nadu had taken precautions,” Stalin said, listing the relief and rescue measures.

A correct weather forecast on the severity of the situation may have reduced loss and damage, said Mano Thangaraj, the state’s dairy development minister.

“It’s important to acknowledge that the unforeseen severity and impact of these events could have been mitigated with more precise and timely forecasts from the India Meteorological Department (IMD),” Thangaraj posted on X (formerly Twitter). “A significant issue was the Time Discrepancy in the weather alerts. The gap between the issuance of the Red Alert and the actual flooding was much shorter than what could have been ideal as some western models exhibit in those countries.”

The cyclonic circulation over Comorin area in south-east Sri Lanka brought heavy rains in the southern parts of Tamil Nadu, said S Balachandran, head of RMC in Chennai. “There was more moisture inside the system than anticipated, which brought widespread rain. This (system) has given more rain than a cyclone,” he said. “We have to expect such types of extreme events because of the climate crisis.”

This magnitude of rain was not expected from such a weather system, said M Rajeevan, former secretary, ministry of earth sciences. “During northeast monsoon, we do see heavy rainfall events, but this was not really expected. So, it’s quite possible that IMD or other agencies did not predict this magnitude of rains,” he said. “Forecasts are made based on dynamic settings of the atmosphere. Moisture played an important role. Sometimes mesoscale systems cannot be seen in typical weather charts. This was seen in the 2005 Mumbai floods.”

Some meteorological parameters and wind convergence over some regions were anomalous, according to Roxy Mathew Koll, climate scientist at Indian Institute of Tropical Meteorology. “There were strong easterly winds, which brought in a lot of moisture. But these rains matched with 2005 Mumbai floods, which was unexpected,” Koll said.

Stalin, who was in Delhi for the opposition INDIA bloc’s meeting, also met Prime Minister Narendra Modi on Tuesday, appraising him of the flooding in the southern districts as well as on the damage wrought by Cyclone Michaung, which submerged Chennai on December 4.

He also wrote to defence minister Rajnath Singh, urging him to deploy more Indian Air Force (IAF) helicopters for relief.

Rescue efforts continue; 800 rescued from train

Authorities and volunteer groups continued rescue efforts across the state’s inundated southern districts, as the water receded amid a pause in the rain.

Meanwhile, 800 passengers who were marooned in the Tiruchendur-Chennai Express at the submerged Srivaikuntam railway station in Thoothukudi for two days were pulled out in batches on Tuesday by IAF and Southern Railway teams.

Read here: CM Stalin says IMD failed to predict the rains correctly

So far, 10 people have died in southern Tamil Nadu, said state chief secretary Shiv Das Meena. Of them, seven were in Tirunelveli and three in Thoothukudi. He added that 12,653 people have been evacuated and moved to 141 relief shelters.

IAF said they rescued four people stranded in Tirunelveli, while the Indian Coast Guard rescued 80 in the district.