Southwest monsoon has been having a sleep walk for the last ten days. Pan India daily rainfall has been persistently less than the normal from 04thAugust onward. Last 2 days, rainfall deficiency has exceeded 65%. Southwest monsoon has gone from ‘above normal’ on 03rdAugust to ‘below normal’ by 15thAugust 2023. The season’s long period average (LPA) stands at 95%, a shortfall of more than 26mm so far. Month of August reel with a huge deficit of 35% and may reach 37% today, the highest so far in the core monsoon months.
There is a small hope for the monsoon activity to pick up, but only in limited areas. A cyclonic circulation is marked over head Bay of Bengal and adjoining Bangladesh. It is likely to consolidate over the same area in the next 24hours. Under its influence, a monsoon low is likely to form over North and Northwest Bay of Bengal within 48hours. It is not expected to be a strong system and will predominantly be manifested as cyclonic circulation, extending up to higher levels of the atmosphere. Nevertheless, some decent showers can be expected for eastern and northeastern parts of the country.
‘Break in monsoon’ is invariably followed by formation of monsoon system over Bay of Bengal. Such a situation revives the monsoon and brings it on track, with active to vigorous conditions over most parts of the country. However, potential low pressure area coming up over head Bay is not promising a big revival. There are two reasons to defy the revival. Formation of system invariably restores the monsoon trough with easterly winds streaming from Bay of Bengal and sweeping Indo Gangetic plains. It is not happening. The low pressure areas mostly move along the monsoon trough. However, in this case, the monsoon trough itself is not getting placed in its normal position. Therefore, the low pressure area, when moves inland on 18thAugust, has a tendency to meander over the eastern parts for the subsequent 3-4 days. It is going to weaken after moving inland and broad cyclonic circulation will remain over Odisha, Jharkhand and Chhattisgarh. Peripherals of this feature, as convergence zone, will extend further to reach East Madhya Pradesh, South Bihar & East Uttar Pradesh and outer lines of Vidarbha in Maharashtra.
Partial revival of monsoon is likely between 18thAug and 24thAug. The beneficiaries will be West Bengal, Odisha, Bihar, Jharkhand, Uttar Pradesh and Madhya Pradesh, but not in the same order of priority and share of rainfall. Weather activity will be staggered over these parts during this period. The low pressure area, after wandering over the eastern parts will have a tendency, once again to move towards the foothills of East Uttar Pradesh and Bihar. It is likely to break up along foothills of Nepal anytime between 25th-26th August. Monsoon trough is likely to get aligned once again along the foothills and therefore limiting the monsoon activity.