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Heavy rainfall may trigger landslides in northeast, Bengal

Hindustan Times, New Delhi | ByJayashree Nandi
Jul 19, 2020 02:06 AM IST

The met department has issued a red category warning for most of northeast including Assam and Meghalaya, Arunachal Pradesh, Nagaland and sub Himalayan West Bengal on July 19, 20 and 21.

Extremely heavy rains in the northeast could accentuate existing flood conditions and lead to landslides in some areas of the north-eastern states and sub-Himalayan West Bengal, India Meteorological Department said on Saturday.

The met department has issued a red category warning for most of northeast including Assam and Meghalaya, Arunachal Pradesh, Nagaland and sub Himalayan West Bengal on July 19, 20 and 21 and an orange category warning for entire north and northwest India including Delhi, Himachal Pradesh, Uttar Pradesh, Bihar and Uttarakhand for the same period. Red category warning indicates that local and disaster control authorities take action to prevent any flooding or landslide disasters. An orange category warning indicates that disaster management and local authorities should prepare for disaster control.

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“We have started impact based warnings for 12 cities in India including Delhi, Mumbai, Shimla, Dehradun, Shillong, Guwahati and others. When we have a consensus on the likely impact, we issue an impact-based warning. For example, in the northeast particularly Assam, the rivers are already overflowing so landslides and flooding is likely based on our assessments. The World Meteorological Organisation (WMO) has been emphasising that we alert people on the weather will do. The assessment is based on a multi hazard approach,” said RK Jenamani, senior scientist, national weather forecasting centre.

According to WMO’s guidelines on multi-hazard impact based forecast, for impact forecast exposure is considered along with the hazard and vulnerability. These types of forecasts and warnings are designed to provide detailed information precisely on who or what is exposed. Jenamani gives the example of UK Met Office which uses past data of 30 years on natural calamities to issue impact based warnings.

IMD for the first time this month has started issuing impact-based warning in its daily bulletins so that common people understand the significance of a particular weather forecast and take precautions accordingly. Earlier this month when Mumbai faced extremely heavy rains, IMD had warned of localised flooding; disruption of traffic and utilities. On Saturday, IMD warned of landslides in upper reaches and flooding as the impact of extremely heavy rains in the northeast.

IMD in its Saturday bulletin said western part of monsoon trough lies south of its normal position and a cyclonic circulation lies over coastal Saurashtra and neighbourhood. This cyclonic circulation is likely to become less marked during next 24 hours. At the same time, the entire monsoon trough (line of low pressure) is also most likely to shift northwards closer to the foothills of the Himalayas between July 19 and 20. In addition, Interaction between mid-level westerlies and lower level easterlies from the Arabian Sea over northwest India is very likely to start from July 18. Convergence of moist southerly/southwesterly winds from Bay of Bengal over northeast and adjoining east India will also begin from Saturday. The combination of these factors will bring widespread rains to northeast and parts of northwest India, IMD said.

“Brahmaputra in Jorhat and Sonitpur districts and River Beki in Barpeta district are flowing in Severe flood situation with rising trend. Since most of the catchments in northeast India, Sub-Himalayan West Bengal and Sikkim are already saturated there is likelihood of continuation of floods in Severe to Extreme levels for the next 3-4 days. Maximum vigil has to be maintained along the banks of all rivers,” the Central Water Commission warned on Friday.

Monsoon rains in the country are 8% excess as on Saturday; 11% excess over east and northeast India; -17% deficiency over northwest India; 14% excess over central India; 17% excess over south Peninsular India.

“Its very good news that IMD has started issuing impact based forecasts. Until now their forecasts were based on meteorological parameters in terms of say how much it’s going to rain or how hot it may be. But now impact based forecast will consider local infrastructure and impact on people,” said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology (IITM), Pune.

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