The New Secretariat blaze has temporarily affected the Alipore Met office's ability to accurately track atmospheric formations real time.

The disruption in power supply following the fire shut down the radar system enclosed within the giant ball on the roof of the Strand Road landmark that helps the weather office predict rain in the city.

The signature football-like structure that helps many identify New Secretariat from a distance is a fabric dome containing a dish antenna connected to a doppler radar of the Met department.

The dome - Radome - protects the parabolic dish (24ft in diameter) from the elements, said Devendra Pradhan, the deputy director general of meteorology.

Officials said the radar on the New Secretariat roof was imported from Germany in 2002 at a cost of Rs 20 crore. It is one of 16 doppler radars in the country.

"The radar measures the height of clouds hundreds of kilometres away. Once the clouds form, it measures the velocity at which they are moving, their height and how much rain they may cause. The radar also provides a projection, making it possible to predict with considerable accuracy when rain will start and how long it will continue. It also throws up the expected wind speed," Pradhan said.

Case in point, the opening ceremony of the IPL at the Salt Lake stadium on Sunday. Scanning images of the New Secretariat radar, the Met department had correctly predicted that rain would come between 6.30pm and 7pm on the IPL opening night.

According to experts, the parabolic dish rotates 360 degrees on its axis while sending out electromagnetic signals and reaches an elevation of 30 degrees in one cycle of movement. It simultaneously receives signals from the targets.

The radar system became inoperative after the fire prompted CESC to switch off power supply to the building. The supply was restored in the evening following clearances from the fire department and the PWD.

Sources in the PWD said the supply to the entire building, except the blaze-affected seventh floor, would be restored by Friday night, which means the radar should be functional by early on Saturday.

Met department officials in Calcutta said they had other means to make short-term predictions but not as accurately as they do with the help of data from the doppler radarÿ.