Typhoon warning signals are divided into several grades.

Typhoon warning signals are divided into four grades: blue warning signal, yellow warning signal, orange warning signal and red warning signal.

1, blue warning signal

The standard of blue warning signal is that it may or has been affected by tropical cyclones within 24 hours, and the average wind force along the coast or land is above 6, or the gust is above 8 and may continue.

2. Yellow warning signal

The standard of yellow warning signal is that it may or has been affected by tropical cyclone within 24 hours, the average wind force along the coast or land is above 8, or the gust 10 is above and may continue.

3, orange warning signal

The standard of orange warning signal is that it may or has been affected by tropical cyclones within 12 hours, the average coastal or land wind force is above 10, or the gust is above 12 and may continue.

4. red warning signal

The standard of color warning signal is that it may or has been affected by tropical cyclone within 6 hours, and the average coastal or land wind force 12 or gust 14 or above may continue.

The structure of typhoon is briefly described as follows:

1, typhoon eye area

The typhoon eye area is very strange, where the wind is very small and the weather is sunny, with an average diameter of 40 kilometers. The sailors involved humorously called Typhoon Eye "Xanadu".

2. Cloud wall area

The cloud wall area around the typhoon eye is dozens of kilometers wide and tens of kilometers high, which is also called the eye wall. The cloud wall is towering here, the wind is howling, the rain is pouring, the sea is churning, and the weather is the worst.

3. Spiral rain belt area

Outside the cloud wall is a spiral rain belt. There are several rain (clouds) bands that gather spirally around the eye wall. The bandwidth of rain is tens to hundreds of kilometers, and it is several meters long in Qian Qian. There will be showers and windy weather where the rain belt passes.

Baidu Encyclopedia-Typhoon