Southwest monsoon remained mostly on backfoot over Indian region during the core monsoon month of August. Pan India deficit area has increased from 15% to 25% and the excess rainfall area has decreased from 26% to mere 8%, between 01st and 28thAugust 2023. The surplus seasonal rainfall of 105% of long period average (LPA) at the beginning of the month has now nosedived to huge shortfall and is below normal at 92% of LPA, till 28th August. It make take a deep dive in the remaining 3days of the month.
Monsoon systems over the Indian Seas, more so, the Bay of Bengal and the semi permanent feature of monsoon trough are the main drivers of seasonal rains. Storms and typhoons in the western Pacific and South China Sea have a direct impact on the performance of Indian monsoon. El Nino conditions in the eastern and central Pacific Ocean has a strong bearing on development of cyclones around the globe in the tropical region. Warming of ocean surface due to El Nino in the eastern Pacific trigger more number of storms and hurricanes. However, the frequency of hurricanes reduce in the North Atlantic during the hurricane season, lasting from May to November. Currently, there are 3 significant storms in the close proximity of Nino region in the Pacific Ocean. Hurricane ‘IRWIN’ is placed over Eastern Pacific, storm ‘IDALIA’ is heading for Carribeans, hurricane ‘FRANKLIN’ located in the close proximity of Florida and there is another ‘Invest’ area as a potential storm sailing the ocean waters. On to the Western Pacific, there is powerful typhoon ‘SAOLA’ heading for southeast coast of China, storm ‘HAIKUI’, a little distance away may possibly ram Japanese and Korean waters and yet another extra tropical storm ‘08W’ in the open sea heading for higher latitudes.
Storms and typhoons over Western Pacific, South China Sea, Philippines Sea are considered detrimental for the health of southwest monsoon. These oceanic disturbances, may be hundreds of miles away, can impact the monsoon stream across the Indian Seas. Factually, they sap the monsoon current running across the Arabian Sea and Bay of Bengal. The remnants of some of these storms as weak low pressure area may approach the Bay of Bengal to trigger active monsoon systems, to accentuate monsoon activity. But, such occasions remain infrequent and rather far and few. These storms drag the monsoon trough far to the north, close to the foothills, as is the current scenario as well.
Month of August has witnessed a prolonged monsoon ‘break’. The first one for nearly 2 weeks, during 1st half of the month and the 2nd one following closely, and is likely to persist for another 4-5 days. There is likelihood of monsoon circulation coming up over Bay of Bengal, entering from Myanmar region. It may become a low pressure area over Northwest and North Bay of Bengal on 04thSeptember. Degree of confidence remains low at this moment, predicting its track and impact. Spread and intensity of monsoon will increase over the eastern and southern parts. Monsoon activity will pick up over West Bengal, Odisha, Jharkhand, Chhattisgarh, East Madhya Pradesh, North Telangana, Coastal Andhra Pradesh and Vidarbha. The Southern Peninsula lying dormant for last many days will also experience moderate showers over most sub divisions. These conciliatory showers are expected in a staggered manner, occurring between 30st August and 07thSeptember.