Bengaluru is typically known for pleasant weather conditions during November and December. Mild wintry conditions during night and early morning and turning into pleasantly warm days remain the special features of the capital city. Climatologically, January is the coldest month with a mean minimum temperature of 15.8°C which rises by over 2°C in February. Northeasterly winds, moist in nature sweep the city and neighbourhood, throughout during November to January. A combination of moderate breeze and high humidity brings the chill factor. Despite the northeast monsoon season, the city is not known for observing any heavy rainfall during this period. The aviation hazards, having the potential to trouble the aviators, albeit for limited durations, are fog and low clouds during the winter months.
Bengaluru is situated on a plateau with an average elevation of 3,000 feet. Therefore, the day and night temperatures are lower than the adjacent parts of the state. Courtesy, high humidity during the night and early morning, the dry bulb and wet bulb temperatures remain very close to each other. All these factors favour fog formation, invariably dense, surrounding all the airfields like International Airport Devanahalli, city airport HAL (Hindustan Aeronautics Limited) and Air Force airfield at Yelahanka.
The dense to very dense fog formation occurs after midnight and lasts, till early morning. The horizontal visibility reduces to less than 100 meters and occasionally Nil, simultaneously at all locations. The weather conditions for air operations get further compounded with the presence of a layer of very low clouds, between ground and 500 feet, above ground level. Practically, the meteorological conditions lead to suspension of air operations.
But, the good thing is that these adverse weather conditions improve rapidly after the sunrise. Latest by 8 a.m or give another half an hour, the conditions improve phenomenally and become fit for all air operations. However, during that window of 4-5 hours, between 02:00hr-07:00hr, both, the incoming and outbound flights may find diversions and delays, respectively. A similar situation occurred during the last weekend wherein, the flights were either diverted or got stranded at the respective airfields. Exercise needs to be cautioned, both by the operators and flyers, while planning and undertaking air operations during this period.