Why Delhi's hyperlocal forecasts are suffering: Doppler radars remain defunct during monsoon

Delhi rain

Despite the monsoon arriving in Delhi nearly two weeks ago, two of the capital's three Doppler weather radars (DWRs), essential for tracking rain clouds and predicting rainfall, are currently non-functional.

The India Meteorological Department (IMD) relies on three DWRs located at Palam, Lodhi Road and Ayanagar, with ranges of 400km, 250km and 100km, respectively. However, the radars at Lodhi Road and Ayanagar have been out of operation for over a month, leaving forecasts dependent solely on the Palam radar, according to the Hindustan Times.

While IMD officials attributed the shutdowns to routine maintenance, meteorologists warned that the absence of the two radars could impact short-term, localised rain predictions. The Palam radar, though covering the largest area, is less precise for hyperlocal forecasts compared to the Lodhi Road and Ayanagar radars, which help track cloud movement and storm intensity more accurately.

“Lodhi Road has been out of operation for nearly two months now. Ayanagar has also been out of operations for over a month,” said Ashwary Tiwari, a meteorologist who runs the page IndiaMetSky on X. “If one has at least Lodhi Road available alongside Palam, forecasts, along with the possible impact time and the area being affected, become more precise,” he added.

DWRs operate on different microwave bands - S, C and X - with varying wavelengths to detect weather systems. The Ayanagar radar uses an X-band, Lodhi Road operates on C-band and Palam uses an S-band.

IMD director general M Mohapatra, however, downplayed concerns, stating that forecasting for Delhi’s monsoon has not been affected. “We will operationalise Ayanagar soon,” he said, as quoted by HT.

Last year, Delhi faced a similar situation when only the Ayanagar radar was functional during heavy rains. The IMD failed to predict an intense downpour that brought 91mm of rain in an hour and over 228mm in 24 hours, highlighting the limitations of relying on a single radar with a shorter range.