'Red alert' in these states: What's behind India's widespread rainfall
The India Meteorological Department (IMD) on Friday issued a red alert for extremely heavy rainfall in several states. Isolated areas in Konkan and Goa, Madhya Maharashtra, Telangana, South Interior Karnataka, Coastal Karnataka, Gujarat, Coastal Andhra Pradesh and Yanam, Vidarbha, southern Chhattisgarh, and South Odisha are expected to witness extremely heavy rainfall. Additionally, orange and yellow alerts for very heavy and heavy rain respectively have been issued for various states in northern and central India.
Southwest monsoon active over large portion of India
Notably, for the first time this season, the southwest monsoon has become active over a large portion of India, with widespread rainfall reported in at least 80% of the country last week. The monsoon, which was subdued during mid-June, gained momentum toward the end of June and covered the entire country by July 2. This is six days ahead of its normal schedule. Let's take a look at what is causing this extensive rainfall.
Westerly winds leading to rains
Over the last few days, heavy to very heavy spells of rain have been reported in Assam, West Bengal, Uttar Pradesh, Uttarakhand, Gujarat, coastal Maharashtra and Karnataka, Kerala, and Lakshadweep. Delhi, Punjab, Uttarakhand, Uttar Pradesh, Himachal Pradesh, Rajasthan and Jammu and Kashmir also received the monsoon spell in early July. The widespread rainfall is a result of the continuous incoming of moisture-laden strong westerly winds from the Arabian Sea.
Monsoon trough, other weather systems enhance rainfall
The position of the monsoon trough—a semi-permanent low-pressure area extending between Pakistan and the Bay of Bengal during the monsoon season—is another factor contributing to the enhanced rainfall. When it moves southward, more rainfall can occur in central, eastern and peninsular India. Other systems—an off-shore trough between south Gujarat and north Kerala, intermittent development of a wind shear zone between central and peninsular India, and a low pressure system over the west-central Bay of Bengal—have also contributed to widespread rainfall.
Rainfall statistics show near-normal monsoon season
The IMD's rainfall statistics indicate that all-India rainfall increased from 242mm on July 9 to 305.8mm on July 17. The country's rainfall stands at 97% of normal for this time of season. Seventeen states have either received normal or above-normal rainfall this season, while some states including Odisha, Haryana, Chandigarh, Himachal Pradesh, and Jharkhand have seen deficient rainfall so far.
Flash flood alert issued due to heavy rainfall
The IMD has issued a flash flood alert for south and central India due to heavy rainfall. The return of the El Nino-Southern Oscillation (ENSO) to a neutral phase and expectations of the cooler La Nina phase forming in the latter half of the monsoon season are contributing to heavy downpours. The IMD has also issued a red alert for Maharashtra, Goa, Kerala due to very heavy rainfall and thunderstorms.
Increased monsoon activity predicted for Central India
The weather service predicts increased monsoon activity in the Peninsula and surrounding central India over the next four to five days. The southwest monsoon is expected to remain active all through this week over south peninsular eastern India and over the Himalayan states. A fresh low pressure system will develop over northwest Bay of Bengal around Friday, which will keep the monsoon momentum high with rainfall persisting over eastern and central India regions during next five days.
