Haryana, Chandigarh, Delhi and Punjab are likely to receive scattered heavy rainfall on August 17 and 18, while Himachal Pradesh and Jammu, Kashmir and Ladakh are expected to witness more intense rain.The IMD has also warned of isolated very heavy rainfall over the western Himalayan region.
The All India Weather Summary and Forecast Bulletin, issued by the National Weather Forecasting Centre at 8.57 am on August 17, said fairly widespread rain is likely over Haryana, Chandigarh, Delhi and Punjab on August 18. Scattered rain is expected over the other parts of northwest India.
The IMD has forecast scattered heavy rain over Haryana, Chandigarh, Delhi and Punjab on both August 17 and 18. The Day-1 warning for August 17 specifically lists these areas as at risk of heavy rain.
The rain is expected to cover more areas on August 18, with fairly widespread to widespread rain forecast over Haryana, Chandigarh, Delhi, and Punjab. The Day-2 warning still predicts heavy rain in some places over Haryana, Chandigarh, Delhi and Punjab.
The forecast is stronger for the western Himalayan region. The IMD has predicted scattered very heavy rain over Himachal Pradesh on August 17 and 18 and over Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad from August 17 to 19. Uttarakhand is also likely to get scattered very heavy rain on August 17.
For August 17, heavy to very heavy rain is very likely in some places over Himachal Pradesh, Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad, Uttarakhand and Uttar Pradesh, as well as Arunachal Pradesh, Chhattisgarh, East Madhya Pradesh, Gangetic West Bengal and Jharkhand.
Haryana, Chandigarh, Delhi and Punjab are separately listed for scattered heavy rain.
On August 18, heavy to very heavy rain is very likely in some places over Himachal Pradesh, Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad and East Uttar Pradesh, as well as Arunachal Pradesh, Jharkhand, West Bengal and Sikkim. Heavy rain is forecast in parts of Haryana, Chandigarh, Delhi, Punjab, Uttarakhand, and West Uttar Pradesh.
The IMD expects the rainy period in the western Himalayan region to continue through the week. Fairly widespread to widespread rain is likely over Himachal Pradesh, Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad and Uttarakhand during August 17-23.After the very heavy rain period on August 17-18, Himachal Pradesh is likely to get scattered heavy rain during August 19-23. Uttarakhand is expected to get scattered heavy rain during August 18-23. Heavy rainfall is forecast over Himachal Pradesh and Uttarakhand, while Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad could still receive heavy to very heavy rainfall at isolated places.Heavy rain is likely in parts of Himachal Pradesh and Uttarakhand on August 20 and 21. The forecast continues to list both hill states for scattered heavy rain on August 22 and 23.
The IMD has also issued a 24-hour flash-flood risk outlook valid till 5.30 am on August 18, showing a low to moderate flash-flood risk over some river areas and nearby places in parts of Himachal Pradesh, Jammu and Kashmir-Ladakh and Uttarakhand.
In Himachal Pradesh, the risk covers Chamba, Kangra, Mandi, Shimla and Sirmaur districts.
In Jammu and Kashmir and Ladakh, the districts/areas listed are Doda, Kathua, Udhampur and Ladakh (Leh).In Uttarakhand, the flash-flood risk covers the districts of Bageshwar, Chamoli, Champawat, Dehradun, Garhwal Pauri, Garhwal Tehri, Nainital, Pithoragarh, Rudraprayag, and Uttarkashi.
The IMD said water may flow on the surface or cause flooding over some fully soaked soils and low-lying areas in the affected regions due to expected rain over the next 24 hours.
The current weather is being affected by several weather systems. According to the IMD's analysis based on observations at 5.30 am on August 17, the previous day's clear low-pressure area over the northwest Bay of Bengal and nearby West Bengal-north Odisha coasts had moved almost northwest and strengthened into a depression.
The depression was centred over coastal West Bengal, adjoining Bangladesh, and the northwest Bay of Bengal, near latitude 22.5 N and longitude 88.3 E, close to Kolkata. It was about 80 km west-southwest of Satkhira in Bangladesh, 160 km southeast of Bankura in West Bengal and 180 km northeast of Baleshwar in Odisha.
The system is very likely to move northwest towards Jharkhand across Gangetic West Bengal during the next 24 hours.The monsoon trough at mean sea level was passing through Firozpur, Dehradun, Bareilly, Sultanpur, Daltonganj and Jamshedpur, then through the centre of the depression over coastal West Bengal and adjoining Bangladesh and the northwest Bay of Bengal before extending southeastwards to the northeast Bay of Bengal.An upper-air cyclonic circulation over northwest Uttar Pradesh persisted at 0.9 km above mean sea level. Another upper-air cyclonic circulation was present over Jammu Division and neighbourhood at 5.8 km above mean sea level, with a trough aloft.
Rainfall observations from 8.30 am on August 16 to 5.30 am on August 17 showed rain at most places over Punjab and Uttarakhand, and at many places over Jammu and Kashmir and Ladakh.
The IMD bulletin also clarified that a red-colour warning does not mean a "Red Alert"; the red colour means "Take Action." Forecasts and warnings for each day are valid from 8.30 am on that day until 8.30 am the following day.