Influencing factors of aviation weather forecast

The minimum standards for aircraft take-off and landing, that is, the basic standards that must be met, are actually weather standards, including wind power, visibility and cloud bottom height. For different airports, runways, aircraft types, aircraft performance and different captains, the standards for aircraft take-off and landing may be different. Sometimes, passengers see some planes take off, but their own planes can't take off. Maybe it's because the takeoff and landing standards are different.

Among many weather phenomena, thunderstorms, low visibility, low clouds, low-altitude wind shear, typhoons, bumps, ice accumulation and volcanic ash clouds are the main threats to flight safety.

Thunderstorm is one of the worst and most dangerous weather encountered by aircraft in flight. Thunderstorm area has always been regarded as a "forbidden area" for flight activities. If the only way is blocked by Lei Yun, then the plane can't take off. Therefore, sometimes the take-off airport and landing airport are both clear-sky Wan Li, but the delay or cancellation of the plane may be due to bad weather such as thunderstorm on the flight route.

Low visibility weather has a great influence on the take-off and landing of aircraft. Rain, clouds, sandstorms, floating dust, smoke, fog and haze will reduce visibility and affect flight. The visibility on the ground is low, and it is easy to yaw and get lost, which affects the take-off and landing. When the visibility of the airport is less than 350 meters, the plane cannot take off; When it is less than 500 meters, the plane cannot land; If the visibility is less than 50 meters, the plane can't even taxi, and improper operation by the pilot can easily lead to flight accidents.

Low cloud is also one of the dangerous weather that endangers flight safety, which mainly affects the landing of aircraft. If the airport is covered with low clouds, the plane will be very close to the ground after flying out of the low clouds. If the plane is not aimed at the runway at this time, it is often too late to correct it, which is easy to cause a go-around. Sometimes, due to improper command or operation, the plane may collide with obstacles on the ground, causing accidents.

Low-altitude wind shear refers to the sudden change of wind direction and wind speed in a short distance below 600 meters near the ground. Strong wind shear will make the plane go around prematurely or forcibly, and under certain conditions, it will also cause the plane to stall and be difficult to control, and even lead to flight accidents. Low-level wind shear is formed under certain weather background and environmental conditions. Strong convective weather such as thunderstorms and tornadoes can easily lead to strong low-level wind shear; Strong low-level wind shear often exists on the front, especially in the windy area after the strong cold front and the strong cold front. In addition, complex terrain is also prone to wind shear, such as Linzhi Milin Airport, Jiuzhai Huanglong Airport, Hong Kong International Airport, and Juneau Airport in Alaska, USA. The terrain is complex and the wind shear is obvious.

Ordinary people have many questions about flight safety, delay and cancellation. For example, the city where the destination airport is located has good weather conditions and good visibility, and the airport is also taking off and landing normally. Why is it still delayed because of the weather? Why wait until the destination airport informs you that you can't land because of the weather, you can alternate to other airports or return, and some planes can land normally? Sometimes when the plane is flying, it will bump for a moment or for a long time. Why?

Zhou Jianhua, deputy director of the Civil Aviation Meteorological Center, said that normal flights are affected by the weather at the departure airport, the weather at the destination airport and the weather on the route, and different routes are affected by the weather to different degrees.

Although the meteorological department of civil aviation will rely on advanced equipment to continuously issue more accurate weather change trend forecasts to facilitate flight operation and scheduling, the weather conditions are constantly changing and it is difficult to accurately judge. This will lead to a sudden deterioration of weather conditions when landing, making it impossible for the plane to land. For safety reasons or fuel shortage, the plane will have to alternate to other airports.