New Delhi, Oct 31 (IANS): Stubble burning in Punjab and Haryana reached its peak this season extending the toxic air quality in Delhi for the third day on Thursday as persisting calm surface winds prevented dispersion of pollutants.

According to Safar India, with an air quality index (AQI) of 412, the overall air quality in the national capital continued to be in the severe category -- most polluted.

The calm surface wind prevailing over the last two days over Delhi has led to strong surface nocturnal inversion and accumulation of pollutants.

The effective stubble fire counts in Northwest India (Punjab and Haryana) increased from the previous day's 1,057 to 2,396, as is evident from SAFAR-multi-satellite fire product.

The stubble fire percentage contribution to Delhi's air quality which touched the season's highest share on Wednesday was 35 per cent, is predicted to be 27 per cent on Thursday and 25 per cent on Friday.

According to Safar India, the transport-level wind direction is forecast to be Northwesterly for the next three days and favourable for plume transport.

An increase in surface wind speed is expected by Thursday when AQI is forecast to slightly improve.

A fresh western disturbance with a trough between 3.1 & 3.6 km above mean sea level runs roughly along the Afghan-Pakistan border as of Thursday. It will approach northwest India by Saturday.

The Western disturbance is likely to influence Delhi's air quality positively. An improvement to the lower end of the very poor category is expected by November 2.