What's the weather like at the warm front?

A, according to the moving direction of cold air mass and warm air mass in the picture and the slope of the front, it can be judged that the front is a warm front, so it is correct;

B, according to the moving direction of the cold air mass in the picture is opposite to that of the warm air mass, it can be judged that the front is a cold front, so it does not meet the meaning of the question;

C, the surface at the junction of cold and warm air masses is called the front. In this picture, the cold and warm air masses move in the same direction, which does not meet the meaning of the question;

D, according to the upward central airflow in the picture, the cyclone in the picture can be judged, so it does not meet the meaning of the question.

So choose: a