Color division of rainstorm warning grade

The rainstorm warning signal is divided into four levels, which are represented by blue, yellow, orange and red respectively.

Blue rainstorm warning signal:/kloc-within 0/2 hours, the rainfall will reach more than 50 mm, or it has reached more than 50 mm, which may or has affected and the rainfall may continue.

Yellow rainstorm warning signal: Within 6 hours, the rainfall will reach more than 50 mm, or it has reached more than 50 mm, which may or has affected and the rainfall may continue.

Rainstorm orange warning signal: within 3 hours, the rainfall will reach more than 50 mm, or it has reached more than 50 mm, which may or has already caused a great impact, and the rainfall may continue.

Rainstorm in red warning signal: within 3 hours, the rainfall will reach 100 mm or above, which may or has already caused serious impact, and the rainfall may continue.

Causes of rainstorm formation

The main weather systems that cause large-scale rainstorm in China are fronts, cyclones, shear lines, eddies, troughs, typhoons, easterly waves and intertropical convergence zone. In addition, thermal thunderstorms will also cause short-term and small-scale heavy rains in arid and semi-arid areas.

In China, the water vapor of rainstorm comes from the South China Sea or the Bay of Bengal. Second, from the East China Sea or the Yellow Sea. Sometimes, in a rainstorm, water vapor comes from the east and south, or mainly from the south in the early stage and from the east in the later stage. The spread of "southeast wind, rain ancestor" in the Central Plains is an objective reflection of the precipitation law.

Like running water, the motion of the atmosphere often produces fluctuations or eddies. When two air streams from different directions or different temperatures and humidity meet, fluctuations or vortices will occur. The largest is several meters in Qian Qian, and the smallest is only a few kilometers. In these fluctuating areas, with the operation of air flow, upward movement often occurs, and horizontal water vapor quickly concentrates in the same area, forming a rainstorm center.