In 15 days of July, Mumbai got 40% of monthly average rainfall

Fifteen days into July, the city has received 40% of the normal rainfall for the entire month

Fifteen days into July, the city has received 40% of the normal rainfall for the entire month. This comes to a total of 333.5mm of rain, against the monthly average of 827mm. The situation is in sharp contrast to the last year’s monsoon, when the city had recorded 927mm of rain by July 16, surpassing the seasonal normal.

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Officials said this trend is indicative of an erratic monsoon season — characterised by heavy, intense showers concentrated over fewer days — but clarified that there is no cause for alarm, as the city has recorded near normal levels of rainfall across the season (from June 1 to June 15).

“In total, there has been about 1295mm of rainfall since June 1, which is 97% of the seasonal normal of 1332.5mm up to the end of July. The long period average for only the first 15 days of July comes to about 402mm of rain. Mumbai’s monitoring station in the suburbs has received 333.5mm of rain, which is only a 17% departure from normal,” said a spokesperson with the India Meteorological Department’s (IMD) regional forecasting centre in Mumbai.

In all, the city has so far received 58.7% of the total seasonal rainfall expected up to the end of September. That’s 1295mm against the long period average of 2205mm. On July 16 last year, the city had received the same proportion of its seasonal average, the IMD official pointed out.

Akshay Deoras, an independent meteorologist and PhD researcher at the University of Reading, said, “The sum is the same, but rainfall distribution this year is skewed. This is not a new or alarming trend, and you can’t make any assumptions based on a single year’s experience, especially because inter-annual variability of rainfall is a normal phenomenon. This July though, Mumbai is likely to receive below-normal rainfall because the forecast for the remaining two weeks is not very promising.”

While this does not have very large implications for public life, but it does for water resources. The total level of useful content in the seven lakes which feed Mumbai, for example, is only 17.35% this year (as of July 14), while it was 23.98% in 2020. In absolute numbers, there are 251,119 megalitres of useable water available to the city currently, as against 347,123 megalitres around the same time last year.

After a particularly heavy spell early on Wednesday, Mumbai clocked in only 3.2mm of rain in eight hours on Thursday, according to the automatic weather station in Santacruz — which is taken as representative of the entire city. A slowdown in rainfall intensity (along with an increase in temperature) is expected to prevail over the next few days. This is the case for most of the state. “After witnessing many days of active monsoon conditions, most of Maharashtra is now expected to witness reduced or low-rainfall activities in the remaining days of July if one considers the current extended-range forecast,” Deoras said.

As per official forecasts, the maximum temperature over the next five days is expected to rise to 32 degrees Celsius (up from 30.6 degrees Celsius on Thursday evening), and the minimum temperature will rise to 26 degrees Celsius — up from 24.6 degrees Celsius on Thursday morning.