Heavy to very heavy rains have lashed Northeast India over the past 48hr with 3 digit rainfall in 24hr at some places. Rains have been more intense over Sikkim, Assam, Meghalaya and Arunachal Pradesh. Nagaland, Manipur, Mizoram and Tripura have received light to moderate showers. The chief amounts of rainfall recorded in the past 24hr are Darjeeling: 111mm, Cheerapunji : 174mm and Passighat: 77mm.
Monsoon trough has now shifted entirely along the foothills with meteorological conditions of ‘break monsoon’. Such situation becomes conducive for heavy downpour over northeast region. Sikkim, Sub Himalayan West Bengal, Arunachal Pradesh and locations on either bank of Brahmaputra become vulnerable for extremely heavy rains. Mountainous terrain of Meghalaya accentuates the weather activity and the ferocious rains over Shillong, Cheerapunji, Barapani, Nongpoh and Tura invariably lead to landslides disrupting communication and connectivity.
Break monsoon conditions are likely to cease in the next 72hr and the rain intensity will reduce to moderate at most places. A cyclonic circulation is expected to form over Northwest Bay of Bengal on 27thAug and pick up strength in the subsequent 24hr. There is possibility of formation of low pressure area, albeit a feeble one, on 28-29 August over Bay of Bengal, off Odisha coast. This feature will pull the eastern end of monsoon trough southward, ending break monsoon over northeast India to start with. Subsequently, the entire monsoon trough is likely to shift south of its normal position at mean sea level, all along its stretch. This condition will arrest heavy rains over northeast India from 29thAug onward and weather activity will remain mild thereafter at least for one week.
Northeastern states are rain deficit in this monsoon season. More prominently, state of Manipur has a large deficit of 58%, followed by Nagaland and Arunachal Pradesh with respective shortfall of 25% and 24% between 01stJune and 25thAugust. The other states have deficiency of 20% or less for the season. This wet spell will help recover the deficiency, though marginally. However, subsequent spell of weak rainfall may again raise the seasonal shortfall across the entire region.