The warning system to be composed of infra-sound sounding net and single thunder warning station by use of VLF and IF-sound emitted from lightning was developed in 1995.After that,during three years(1995~1997) the system ran on in the 4~6 months every year and forecast 21 strong thunder storms.The convection 17 m/s gale had been happened in Northern Bay of South China Sea since the IF-sound signal appeared 3~6 hours in advance.From April to June 1997,the seven catastrophic convection thunderstorms had been forecasted by the authors and had been protected by NHOC before it appeared 40 minutes ago.The nowcast decreased the loss about seventy million RMB predicted.In the strong convection weather system,the strong turbulence exists in the beginning,a lot of the vapor phase changes and water drops increase and grow up with the turbulence in the unstable cloud,and the charge accumulate or release go on,the drops grow up with collision and electric attraction again and again,turbulent and entrainment motion might be caused selforganization and positive feedback.Consequently the turbulent motion would evolute to some single direction motion(prosconvection) and then emit the IF-sound if the conditions exist for very strong extra-unstability and more moisture exchange.By the time the turbulent motions develop to the convection that can emit another long period IF-sound.The results show that the pros 1~2 seconds period IF-sound wave of the turbulence is different from 5~100 seconds period of IF-sound waves of the convection,besides,the waves pattern don't show dispersion and always appear in half amplitude form.The mechanism has been discussed.