India Meteorological Department (IMD) has said that a low-pressure area has formed on Monday morning off the South Odisha coast over the Bay of Bengal, and this will likely be followed up by another ‘low’ over the next five days (by Friday), lending a sudden but expected boost to the monsoon as it enters the second half of July, normally the rainiest of the four months.

Such a denouement was in the offing after the West Pacific/South China Sea next door to the Bay of Bengal and across Indochina got activated, generating helpful westward-moving ‘pulses’ that land up in the Bay only to get intensified as full-fledged low-pressures areas ((low’s). Short-to-medium guidance from India Meteorological Department (IMD) had pointed to this prospect.

Ideal conditions spawn

This also brought the main monsoon trough over land that lay extended on Monday from Jaisalmer, Kota, Guna, Damoh, Pendra Road, Sambalpur and Puri before dipping into the Bay where the ‘low’ has formed. This alignment of the trough over land linked with a ‘low’ in the Bay sets up most ideal conditions for the monsoon to train moisture from the sea into land and drive rain into the farming interior. Heavy rain and floods are to be expected over Central and North-West India as the ‘low’ navigates the trough. The stakes are high since a follow-up ‘low’ is expected to tread more or less the same path over land.

A combined outlook from the Climate Prediction Centre, National Centres for Environmental Prediction and the National Oceanic and Atmospheric Administration of the US tends to agree suggesting enhanced rainfall over Central, West and East India during July 17 to 23 coinciding with roaring activity in the South China. This will generate one ‘low’ after the other, it now transpires. 

Active South China Sea

The IMD projections drop enough hints suggesting a monsoon ‘pulse’ originating from the South China Sea wending its way West across Indochina into the Bay where it is seen as dropping anchor and evolving as a full-fledged ‘low’ (even depression). It would gradually guide itself towards the Odisha-Andhra Pradesh coast, buffeted as it would be by strong easterly winds from the Bay..

Activity would be muted over Peninsular India, especially extreme South Peninsula, before returning to normal during the week that follows (July 24 to 30) when the South China Sea may tone down pitch by a notch, with corresponding cool-off in monsoon intensity over India and most of the rainfall getting confined to Central India (Gujarat-Madhya Pradesh-Chhattisgarh-Odisha). 

Helpful monsoon features 

Meanwhile on Monday the IMD identified the monsoon-driving features as the main trough over land lying South of its normal position, indicating active monsoon conditions. It is likely to stay in this alignment for the next four-five days. To the West, the offshore trough ran near-full-blown from South Gujarat to North Kerala coasts. Expected arrival of a western disturbance into North-West India and its movement into the plains to meet up with monsoon south-easterlies will bear some watching.  

Heavy to very heavy rain 

A five-day outlook said heavy to very heavy rainfall is likely over Konkan & Goa; Kerala & Mahe; Coastal and South Interior Karnataka; Madhya Maharashtra; and Gujarat. Isolated extremely heavy rainfall is likely over Konkan & Goa and the ghats of Madhya Maharashtra on Monday and Tuesday; and over Coastal Karnataka, South Interior Karnataka and Kerala & Mahe on Monday. It will be isolated very heavily over Vidarbha; Telangana; Coastal Andhra Pradesh & Yanam; North Interior Karnataka; and Marathwada.

Towards East India, the IMD sees the possibility of heavy rainfall at isolated places over Odisha on Monday, Wednesday and Thursday; over Arunachal Pradesh for three days from Monday; Assam & Meghalaya; hills of West Bengal & Sikkim; and Bihar on Monday; and over Nagaland, Manipur, Mizoram & Tripura on both Monday and Tuesday. Isolated heavy rainfall is likely over Uttarakhand and East Rajasthan for five days from Monday; and over East Uttar Pradesh on Monday and Thursday. 

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