Abstract: A case study indicates that the circulation adjustment associated with the strong cold wave provides a favourable background for the explosive development of the cyclone. When the coupling of ultralong and long wave troughs occurs in the coast of east Asia, the cyclone beneath the southwest current of the trough will develop rapidly. The deepening of the trough accelerates the upper level jet obviously. Then the area of the jet stream expands downwards. The secondary circulation around the exit area of the jet strengthens with the speeding up the jet, which tends to faster the development of the cyclone. Most explosive cyclones, occur ahead of large-scale major trough at the north fringe of the exit area of jet.