New Delhi, Nov. 14 -- The Capital recorded a third consecutive day of 'severe' air on Thursday, with AQI readings consistently above the 400 mark. This, despite the Centre's Early Warning System (EWS) - the model that triggers Grap measures - forecasting 'very poor' air for Tuesday, Wednesday and Thursday, underscoring a widening gap between projections and actual pollution levels. On Tuesday, despite an earlier EWS forecast that the AQI would stay in 'very poor', Delhi recorded the first 'severe' day of the season. Since then, it has stayed above 400 ('severe') for three days despite EWS's forecasts. Meanwhile, a 50-point improvement was seen Gurugram's air quality index (AQI) which stood at 300 on Thursday as compared to 350 on Wednesday, according to CPCB's 4pm live feed. According to the Central Pollution Control Board (CPCB), an AQI of above 400 falls under the 'severe' category. Between 301 and 400 is classified under 'very poor'; 201-300 under 'poor'; 101-200 under 'moderate'; and 51-100 under 'satisfactory'. The EWS is operated by the Indian Institute of Tropical Meteorology (IIT-M), Pune, under the Union ministry of earth sciences. IIT-M also manages the Decision Support System (DSS), which estimates the contribution of various sources, such as stubble burning and vehicular emissions, to Delhi's pollution. IIT-M officials did respond to HT's requests for comment. Experts said multiple factors may explain the gap between the projections and the current situation, including assumptions within the model that on-ground enforcement of anti-pollution measures would reduce pollution. On Tuesday, the Commission for Air Quality Management implemented Stage 3 measures, for AQI above 400, under its Graded Response Action Plan (GRAP). "The model assumes certain actions will kick in under Grap, leading to some improvement on that front. So this shows that some sources have not been cut down effectively as they should have," said Sunil Dahiya, founder and lead analyst at the environmental think-tank Envirocatalysts. "We have also seen that DSS and EWS are reliant on an older emissions inventory, meaning despite dynamic weather forecasts, the overall end product is inaccurate." CPCB data showed that, apart from Delhi (404), only two other cities in India recorded 'severe' pollution on Thursday - Bahadurgarh (466) and Rohtak (430) in Haryana. Meteorological conditions have remained unfavourable since Tuesday, compounding the situation. Slow wind speeds and low temperatures have triggered inversion - when a layer of warm air lies above cooler air near the surface, thereby trapping pollutants and preventing their dispersion. "Winds were expected to increase marginally on Thursday, but that did not happen. They stayed between 5-7 km/hour through the day and became calm again at night," said Mahesh Palawat, vice president at Skymet. No significant change in wind speed or temperature is expected over the next few days, he added. The EWS bulletin on Thursday said Delhi's AQI is expected to remain 'very poor' from Friday to Sunday. "The outlook for the subsequent six days from Sunday says the air quality is likely to be between 'very poor' and 'severe' categories," it said. According to IMD, Gurugram's minimum temperature on Thursday stood at 10degC, meanwhile, the maximum was at 26degC....