Within a span of 48 hours, Pune has experienced two of the wettest days of the month, with the 24-hour rainfall data exceeding the month’s average rainfall both times. The city has already recorded 339 per cent surplus rainfall in the 18 days of this month. Why is Pune experiencing an extremely wet October this year? We explain. Is October a rainy month for Pune? The rainiest month in a calendar year for Pune is July, when the city records an average monthly rainfall of 186.6mm. The second rainiest is June, with average monthly rainfall of 138mm. In comparison, the city generally does not get heavy or very heavy (64.5 to 204.5mm in 24-hours) rainfall in October, and the India Meteorological Department (IMD) considers 67.8mm as the month's average. As October is the first month of the post-monsoon season, Pune remains under the influence of the Southwest monsoon, which normally withdraws after October 10. There are a few short but intense rain spells due to thunderstorms, mainly in the afternoon or evenings, but they don't last long. At other times, the weather generally stays hot and dry. However, there have been five other occasions since 1980 when the city recorded exceptionally high rainfall in October. These include 2020 (312mm), 1993 (268mm), 2019 (234.9mm), 2011 (206.7mm) and 1999 (200.5mm), the IMD rainfall data suggests. If rains persist in the coming days, which the IMD has forecast, October 2022 could feature among Pune’s wettest October months. How much has it rained? From October 1 to 18, Pune city (Shivajinagar) has recorded 263.9mm. By October 11, the city received 72.8mm rainfall, already higher than the monthly average of 67.8mm. Then came two major wet spells within four days. Under two hours of October 15, Shivajinagar recorded 74.3mm and the 24-hour rainfall data of October 16 was 78mm.Within 90 minutes on Monday (October 17), rains again lashed Shivajinagar and the rainfall figure touched 81mm. The 24-hour rainfall on Tuesday (October 18) was 104.5mm. To put this in better perspective, Pune’s surplus rainfall of 170 per cent on Monday jumped to 339 per cent by Tuesday for October so far. Notably, all the wettest October days by far have been recorded since 2010. What caused the deluge? Since last week, Maharashtra has been under the influence of moisture-laden winds from both Arabian Sea and Bay of Bengal. Initially, these winds gained strength due to the presence of a cyclonic circulation off the Maharashtra-Goa coast in the Arabian Sea, resulting in moderate to heavy rainfall all of last week over Madhya Maharashtra, including Pune, Marathwada, Vidarbha and Konkan. Once this cyclonic circulation dissipated, the rainfall continued owing to the enhanced moisture in areas where the Southwest monsoon is yet to withdraw. During the last weekend, a fresh cyclonic circulation developed and remained located off Kerala coast. This system once again kept the supply of moist winds over Maharashtra, which in turn, strengthened the development of cumulonimbus clouds over Pune and neighbourhood areas, both on October 15 and 17. The ongoing rainfall activity is mainly due to moderately strong Southwest monsoon affecting Maharashtra.
