Satellite pictures don't aid cyclone tracking: Experts

Trail of destruction left by cyclone Thane was unexpected

Satellite pictures are not of much help in tracking cyclonic storms as they move closer to the coast when greater precision and detailed data is needed to save human lives, weather experts have said.

“Met satellites” may be good for “general weather monitoring”, but the latest “Thane” tropical experience, which devastated parts of North Tamil Nadu and Puducherry, has proved the resilience and greater reliability of the “Doppler Weather Radars (DWR)” of the Indian Meteorological network.

Sharing their experience at a “Review of the 2011 Monsoons” (both South-West and North-East) at the Regional Meteorological Centre (RMC) here on Wednesday, S P Thampi, senior scientist at the DWR station in Chennai said satellites, unable to pierce the cloud formations, were at best able to give pictures of evolving storms “one hour before”.

But it was the DWR—the one commissioned in Chennai by IMD completes ten years in service on February 20—which saved the situation for the weathermen this time in tracking the “Thane” cyclone from December 28, tailing its movement “every ten minutes”, and in capturing the finer details of the “spatial and temporal dynamics” of the storm system.

The radar pictures precisely showed how the eye of the “very severe cyclonic storm,” as it moved towards the coast “gets narrower and narrower.” Thus, the RMC here was able to furnish virtually minute-to-minute information for All India Radio’s hourly bulletins, and to government authorities in Tamil Nadu and Puducherry to take relief steps.

Despite the “La Nina” (the wider ocean atmospheric phenomenon and the counterpart of
“El Nino” that influences surface sea temperatures) conditions persisting during the “Thane” cyclone, the season ended with “excess rainfall” in Tamil Nadu, said Y E A Raj, Deputy Director General of Meteorology, RMC.

Stating that the North-East Monsoon (NEM) from 2004 to 2011 (officially declared to have ended on January 12), have been “unusually above normal”, Raj said: “We did not expect the NEM to go into an excess mode last year. But ‘Thane’ changed all that. It was a very complex relation how phenomena like ‘La Nina’ impact Indian monsoons.”

If the sea surface temperature had been lower, “Thane” while approaching the coast could have weakened. But the temperature then was 26 degrees Celsius and had it been higher, say 30 degrees, “Thane” could have turned into a “super cyclone,” said Dr S R Ramanan, Director, RMC.

Strangely, for all the excess and bountiful rainfall the tropical cyclone had brought to other parts of peninsular India until it went over to the Arabian Sea side, the NEM for the entire season in October-December 2011 was “vigorous and active” only for 20 days, pointed out Dr S Balachandran, another scientist at RMC. This in turn points to climate change patterns.

“Though we were warned sufficiently early about ‘Thane’ cyclone, nobody anticipated the extent of destruction caused by it, particularly the complete collapse of the electricity infrastructure in Cuddalore and parts of Villupuram district,” said K Gnanadesikan, Relief Commissioner, Tamil Nadu.