Rain to bring back chill next week

EXPERTS SAY A western disturbance is likely to trigger showers and a thunderstorm after which the winter chill and dense fog will return

NEWDELHI: A western disturbance is likely to trigger some rain and a thunderstorm in the national capital on Tuesday according to the scientists at the Regional Weather Forecasting Centre (RWFC). This will bring back the winter chill that the Delhiites have been missing.

“We are expecting some rain and a thunderstorm on January 23. A western disturbance is approaching and this may trigger some rain in Delhi and other parts of northwest India,” said Kuldeep Srivastava, a senior scientist of the RWFC.

The last time Delhi received light rain was on December 11, 2017. The day temperature dropped by around five degrees.

“This time too we are expecting some drop in the temperature. If the western disturbance triggers snow in the hills, then we can hope to expect the chill to return,” he said.

The minimum temperature dropped from 9.1°C on Tuesday to around 5.6°C on Wednesday, which was one degree below normal. The maximum temperature also dropped to around 23.1°C from 25.5°C.

As relative humidity will also shoot up after the rains, Met officials have warned that dense fog may return to the city. Weather experts are expecting some dense fog on Thursday morning as the moisture level will increase and wind speed is dropping. On Wednesday morning, the city was engulfed by a moderate fog with visibility around 300 metres at 8.30 am.

“There could be dense fog on Thursday. Visibility could drop to less than 100 metres at Palam and this would require CAT-III operations,” said a senior official of the India Meteorological Department’s unit at IGI airport.

Officials said that south-easterly and easterly winds are blowing and this is helping the moisture level to shoot up. The wind speed has also dropped from around 15km/hour to around 10 km/hour over the last 48 hours.

“With low wind speed and high relative humidity, the air quality of Delhi has already started deteriorating. While the moisture is helping to trap pollutants, the low-velocity wind is failing to disperse them,” said D Saha, head of the air quality laboratory at Central Pollution Control Board.

The air quality, which had improved from ‘very poor’ category on Monday to ‘poor’ category on Tuesday, has once again deteriorated to ‘very poor’ levels on Wednesday. The AQI shot up from 256 on Tuesday to 347 on Wednesday. On a scale of 0-500, an AQI value below 300 is ‘poor’. If the value is between 301 and 400, it is considered ‘very poor’.

SAFAR, which is India’s official pollution forecasting system under the ministry of earth sciences, has warned that levels of particulate matter — PM10 and PM2.5 — would increase at least over the next two days.