Abstract:This paper analyses the convergence characteristics of explosive spiral cloud band of Typhoon Saola by using variety of observation data, wind decomposing, Shuman Shapiro filtering and TREC (Tra cking Radar Echoes by Correlation) wind inversion methods. The results indicate that spiral cloud band formed in the background of large scale convergence from the mesoscale filter wind, variation wind and divergent wind after decomposition. The low level rotational wind was the major contributor to the horizontal kinetic energy input, which strengthened the low layer momentum accumulation. Besides, the divergent wind strengthened the convergence. The upper divergent wind was the major contributor to kinetic energy output, which strengthened the upper divergence. The rotational and divergent wind strengthened the vertical motion, promoting the development of severe spiral cloud band. After surface mesoscale filtering, we could see obvious mesoscale convergence or vortex in the two areas, which were also reflected in higher levels. Thus, the mesoscale convergence zone and spiral cloud band affect each other.