Heat wave warning for Friday, AQI slides

Daytime temperatures on Friday are likely to touch 38 degrees Celsius in the suburbs and 37 degrees in South Mumbai

MUMBAI: Mumbai may experience heat-wave conditions on Friday less than a week after the monsoon withdrew from the city, according to the India Meteorological Department (IMD)

Heat wave warning for Friday, AQI slides

Daytime temperatures on Friday are likely to touch 38 degrees Celsius in the suburbs and 37 degrees in South Mumbai. “According to our definition, if the temperature varies more than 4.5 degrees Celsius from normal, it is considered a heat wave. Since we are expecting temperatures to rise to 38 degrees Celsius, we have issued a warning,” said Bikram Singh, head of the Regional Meteorological Centre (RMC), IMD, Mumbai.

Although temperatures will rise significantly, people may not experience much discomfort as humidity is low. “Unlike in May and June this year, when high humidity had made even temperatures in the range of 34 degrees Celsius difficult to bear, lower humidity at present will make it less uncomfortable,” said Singh.

The city sweltered on Thursday too. The maximum temperature at Santacruz was 37.6 degrees Celsius, 4.5 degrees above normal. Colaba logged 36.5 degrees Celsius, 3.9 degrees above normal.

Prof Gufran Beig, chair professor at the National Institute of Advanced Studies (NIAS) and founder director of SAFAR, said the current heat needs to be viewed in the larger context of the Super El Niño and changing atmospheric circulation. “This Super El Niño of the decade influences large-scale circulation, leading to a relatively warmer winter. This is further aggravated by a deficit monsoon, dry soil, and reduced cloud cover, which allows more solar heating,” Beig said.

Sushma Nair, scientist with the Regional Weather Forecasting Centre (RWFC), said the current heat is due to an anti-cyclonic circulation in the region. “These conditions do not allow air to rise; they stall sea breeze; and cause temperatures to rise, thereby preventing dispersion of pollutants that get trapped near the earth’s surface. This leads to a drop in air quality,” Nair said.

Anti-cyclonic circulation also prevents cloud formation. “With less cloud cover and a delayed sea breeze, daytime temperatures rise and the accumulated heat takes longer to dissipate. This is why the heat can feel particularly intense despite October being a transition month,” said a senior IMD scientist.

Air getting poor

The overall Air Quality Index (AQI) in Mumbai slipped to 120 (moderate) on Thursday, the highest this month. PM2.5 and PM 10 were the prominent pollutants. The last time AQI had dipped close to this number was on October 2, when it reached 110. Although in the moderate zone, the SAFAR app warned that this could cause breathing discomfort for people with asthma, lung and heart disorders. In September, AQI in the city stayed between 36 and 75 (good).

Of the 20 air quality monitoring stations, 14 logged moderate AQI on Thursday. Worli recorded maximum AQI at 159, followed by Deonar at 153 and Siddharth Nagar in Worli at 152. Kandivli (west) registered the best or lowest AQI at 74.

AV Shenoy, a Grant Road resident and transport analyst, noticed a thick layer of smog in the afternoon. “It was so hazy around 12.30pm that I could not see the South Mumbai buildings from the Sea Link, which is unusual,” he said. Under treatment for asthma, the 79-year-old said he now takes two puffs on his inhaler twice a day, up from only one puff at night until recently.