The article presents the results of an application of K1/3 weather coefficient to tropical cyclone avoidance manoeuvre on the example of a tropical cyclones GASTON in the North Atlantic in. Avoidance manoeuvre was planned with the use of the Bon Voyage ORS (Onboard Routing System) of the AWT and also with the use of the programme CYKLON. The routes considered in the Bon Voyage system were generated by the route optimization algorithms of the system and routes programmed manually were generated by the system operator. Weather coefficient K1/3 was utilized as an index of safety of navigation in decision making regarding the ultimate route choice of all route variants generated and programmed in both decision making support systems. Results obtained point at the legitimacy of utilizing several decision support systems in solving the problem of tropical cyclone avoidance manoeuvre.