Delhi and its neighbouring areas witnessed thunderstorms and heavy overnight rain, making Monday the wettest October day in four years, according to India Meteorological Department (IMD). The temperature also dropped to 18.7 degrees Celsius at Delhi’s base station Safdarjung, which is 2.3 degrees below normal. The rain occurred even after the withdrawal of southwest monsoon from the region. According to IMD, monsoon’s retreat doesn’t mean a region will not witness rainfall, adding that there are several factors at play, including other weather systems, changes in wind patterns and moisture in the atmosphere.
The IMD’s October 11 bulletin points to three factors from an active spell of unsettled weather across north India warning of rain in the region. These include a trough extending from northwest Rajasthan to northeast Madhya Pradesh, another trough stretching from a cyclonic circulation over central Pakistan towards north Madhya Pradesh, and a western disturbance over Himachal Pradesh.
A western disturbance is a weather system that originates in the Mediterranean region and moves eastwards, bringing moisture and unsettled weather to parts of north India. It is particularly associated with winter rain over northwest India but can also affect the region during the post-monsoon period.
The IMD bulletin also mentions two troughs. These are elongated zones of relatively low atmospheric pressure, while a cyclonic circulation involves winds rotating around a low-pressure area. Such features can encourage air to rise, leading to cloud formation and, when atmospheric moisture and other conditions are favourable, rainfall and thunderstorms.
Is This A One-Day Spell Or Could Rain Continue?
The IMD’s October 11 forecast expected isolated to scattered rainfall over Haryana, Chandigarh and Delhi from October 11 to 15, with thunderstorms, lightning and gusty winds also likely during October 12-15. It predicted isolated heavy rainfall over Delhi and neighbouring areas on October 11.
The weather department has recomended regulating tourism and recreational activities, including helicopter services, in the Delhi-NCR region. It also said that both onshore and offshore activities need to be judiciously regulated.
