IMD puts heavy rain on 8 September over Bihar, Bengal, Odisha and the Northeast

The India Meteorological Department's evening bulletin on 7 September, issued at 16:39 IST, named 8 September as a day of isolated heavy rain across a long eastern arc: Arunachal Pradesh, Assam and Meghalaya, Bihar, East Madhya Pradesh, East Uttar Pradesh, Nagaland, Manipur, Mizoram and Tripura, Odisha, and West Bengal and Sikkim.

The driver is a low-pressure area over the central parts of Uttar Pradesh, working with the monsoon trough. Isolated very heavy rain had already fallen on 7 September over East Uttar Pradesh, Uttarakhand and West Uttar Pradesh. Bareilly recorded more than 20 centimetres. Parts of Uttarakhand, East Uttar Pradesh and Bihar reported 12 to 20 centimetres.

That matters in Bihar because the Ganga at Gandhi Ghat in Patna had already gone past the August 2016 mark. On 7 September the river stood at 50.57 metres, five centimetres above the 21 August 2016 high. Disaster officials have listed more than 22 lakh people across 12 districts. The 8 September warning sits on top of water that has nowhere left to go in the lowest wards.

Gangetic West Bengal is down for widespread rain from 7 to 10 September, Jharkhand from 8 to 11 September, Bihar from 8 to 10 September, and Odisha from 8 to 9 September and again on 11 September. Sub-Himalayan West Bengal and Sikkim have isolated heavy rain on 8 September and again on 11 and 12 September. Arunachal Pradesh is in for a longer spell, from 7 to 12 September. Assam and Meghalaya are named for 8 September and for 11 and 12 September.

Peninsular India is the exception. The same bulletin said subdued rainfall is likely there for the next six to seven days. The active belt has shifted north and east. Thunderstorms and lightning are listed for Gangetic West Bengal from 7 to 9 September and for Jharkhand on 7 and 8 September and again on 12 and 13 September.

A yellow warning covers parts of East Madhya Pradesh, East Uttar Pradesh, Bihar, West Bengal, Odisha and the Northeast. Isolated heavy rain is the official language. In practice that means a few stations can still record 7 centimetres or more while neighbouring blocks stay dry. The 7 September prints from Bareilly show how wide that gap can be inside a single state.

Northwest India is not empty. Isolated to scattered rain is listed for Jammu and Kashmir, Ladakh and adjoining areas from 7 to 13 September, Himachal Pradesh from 7 to 12 September, and Uttarakhand on 8 and 9 September, with isolated heavy amounts returning to Uttarakhand from 10 to 13 September. Haryana, Chandigarh and Delhi had already seen heavy rain in the previous 24-hour window.

The forecast is a planning document for district magistrates who already have kitchens and boats in the field. Bihar has been running 1,345 boats and 190 community kitchens. Another day of isolated heavy rain over a river that has beaten its 2016 record does not reset those numbers. It adds volume to channels that are already full.

The Northeast warning is separate from the Bihar problem. Arunachal, Assam, Meghalaya and the smaller hill states sit on steep catchments. Isolated heavy rain there is a landslide and flash-flood risk more than a river-gauge risk. The bulletin treats both belts in the same sentence. The ground does not.

What the 8 September map does not do is promise a break. The low over central Uttar Pradesh is still the organising feature. Until it moves or fills, the eastern and northeastern lists stay active. The next evening bulletin will say whether Bareilly's 20-centimetre print was the peak of this pulse or the first of two.