An EF3 tornado occurred in the spiral cloud belt surrounding Typhoon Rainbow on October 4, 2015. We performed six nested numerical simulations with horizontal resolutions of 4050, 1350, 450, 150, 50 and 15 m to analyze the structure and mechanisms of formation of the tornado. The typical structure of the tornadic supercell was simulated at a resolution of 444 m. The tornado-like vortex system developed until the grid spacing was ≤148 m. The suction vortex inside the tornado were captured at a resolution of 15 m. These suction vortices developed and rotated rapidly before being organized into the main vortex of the tornado. We used the vorticity equation to analyze the vorticity budget of the suction vortex. The main contribution to the vorticity was the solenoidal term. The horizontal convergence term mainly influenced the high-level outflow, whereas the tilting term affected the mid-level updraft. The frictional term mainly affected the lower levels where the suction vortex developed. We propose a conceptual model based on our results. Influenced by the frictional force, the suction vortex generated, developed and merged into the tornado vortex near the surface. The vertical circulation of the strong spiral region was influenced by convergence at higher levels and inflow at the lower rear of the tornado. Tilting of the vorticity tube and merging of the suction vortex caused the hydrometeors to aggregate and fall at the location where the tornado was generated.

2015 年 10 月 4 日，台风彩虹周围的螺旋云带发生 EF3 龙卷风。我们进行了 6 次嵌套数值模拟，水平分辨率分别为 4050、1350、450、150、50 和 15 m，以分析台风彩虹的结构和形成机制。龙卷风。以 444 m 的分辨率模拟了龙卷风超级单元的典型结构。直至网格间距≤148 m，形成类龙卷风涡旋系统。以 15 m 的分辨率捕获了龙卷风内部的吸力涡旋。这些吸力漩涡在被组织成龙卷风的主漩涡之前迅速发展和旋转。我们使用涡量方程来分析吸涡的涡量预算。对涡量的主要贡献是螺线管项。水平收敛项主要影响高层流出，而倾斜项影响了中层上升气流。摩擦项主要影响吸涡发展的较低水平。我们根据我们的结果提出了一个概念模型。受摩擦力的影响，吸力涡在地表附近产生、发展并汇入龙卷风涡中。强螺旋区的垂直环流受到高空会聚和龙卷风后下部流入的影响。涡流管的倾斜和吸入涡流的合并导致水凝物聚集并落到龙卷风产生的位置。吸力涡流在地表附近产生、发展并合并为龙卷风涡流。强螺旋区的垂直环流受到高空会聚和龙卷风后下部流入的影响。涡流管的倾斜和吸入涡流的合并导致水凝物聚集并落到龙卷风产生的位置。吸力涡流在地表附近产生、发展并合并为龙卷风涡流。强螺旋区的垂直环流受到高空会聚和龙卷风后下部流入的影响。涡流管的倾斜和吸入涡流的合并导致水凝物聚集并落到龙卷风产生的位置。