Localized Dense Fog Affecting the Airport

Dense fog caused diversion of 13 Hong Kong-bound flights in the morning of 6 April 2008. While fog would typically form at HKIA under light wind conditions or the influence of cold fronts, it was a weak anticyclone covering the Pearl River Estuary that brought the fog to HKIA in that morning. Visibility at HKIA fell to around 2000 m in the small hours of that day, and it suddenly dropped sharply to about 100 m at around 0430 HKT (Fig.1 and Fig.2). Macao and Shenzhen also experienced a sudden drop of visibility in the small hours, while visibility at Guangzhou generally stayed above 1500 m in that morning.

Based on past records since airport opening, there were only a few days with visibility dropping to 200 m or below at HKIA. While the Observatory will continue to enhance observation and forecasting techniques for low visibility, it will still be a challenge to forecast the sudden drop of visibility for such an atypical rare event.

Fig.1: A photo taken at the HKIA in the early morning of 6 April 2008.

Fig.2: Time series of visibility reading for Chek Lap Kok on 6 April 2008.