A yellow alert indicating heatwaves at isolated places has been issued for Mumbai, Thane and Raigad for Wednesday. The coastal belt in the state is reeling under the heat wave since Sunday.
For the fourth consecutive day, Mumbai recorded above normal maximum temperature. On Tuesday, the maximum temperature dropped by three degrees to 37.5 degrees C, and yet, it was five degrees above normal. On Monday, the highest maximum temperature for the year was recorded with day temperature touching 39.4 degrees Celsius which was seven degrees above normal. As per the 48-hour forecast issued by IMD, Mumbai, the temperature is likely to remain 39 degrees Celsius.
The current rising temperature over the Konkan region, which includes Mumbai, is due to the direct lower-level winds from Saurashtra and Kutchh in Gujarat which is reeling under a severe heat wave for the past few days, over the Konkan region. Mumbai is likely to get respite from the heat over the weekend, with the day temperature expected to drop to 36 degrees C.
The night or the minimum temperature also remained above normal on Tuesday. At IMD’s Santacruz observatory, the minimum temperature recorded was 23 degrees C, which was two degrees above normal. As per the 24-hour forecast issued by IMD, Mumbai, the night temperature will remain above normal at 23 degrees C.
Based on IMD’s heat wave definition, between 1973 and 2020, 10 heat waves and two extreme heat wave events were observed in Mumbai. Heat wave is defined based on the temperature thresholds over a region in terms of actual temperature or its departure from normal. For coastal cities like Mumbai, when the maximum temperature departure is 4.5 degrees C or more from normal, and the temperature is above 37 degrees C in at least two stations, a heat wave alert is issued. When the departure is above 6.5 degrees C, a severe heat wave alert is issued.
As per a study conducted by WRI India on Mumbai’s vulnerability assessment for the Mumbai climate Action Plan, the years in which a heat wave event was observed are 1977, 1981, 1985, 1989, 1995, 2005, 2009, 2013, 2014 and 2018. Extreme heat waves were observed in 2004 and 2011.
The analysis shows that from 1973-to 2020, more than half of the observed heat wave events (7 of 12) have occurred in the last 15 years while one-third of them have been frequently observed in the last 10 years.