Xinyang, Henan Province was raided by heavy rain, with the maximum rainfall exceeding 2 12mm. Why is it so heavy?

Mesoscale ground convergence line and MCS triggered by mesocyclone are the direct influence systems of this process; The intrusion of dry air in the middle and upper layers is beneficial to the formation and development of convective unstable stratification, which leads to convective rainstorm. The center of heavy precipitation appears in the stage of convective clouds from strong to mature, and the falling area is located near the MCS center or the head boundary. At the same time, the forced upward movement caused by terrain obstacles promoted and strengthened the development of MCS.