Then, the mesocyclone's lower part becomes tighter, increasing the speed of the wind.

接着，“中气旋” 靠下部分会更紧绷，以此给风加速。

Outside, cool, dry, sinking air starts to wrap around the back of this mesocyclone, forming what's known as a rear flank downdraft.

外部那些干冷下沉气体开始在 “中气旋” 后侧环绕，形成一个 “后侧下环流”。

This unusual scenario creates a stark temperature difference between the air inside the mesocyclone, and the air outside, building up a level of instability that allows a tornado to thrive.

这种情景使 “中气旋” 内外部气体间产生了非常明显温差，由此造成更高一级不稳定性使龙卷风更加猖狂。