Traffic distribution in a wireless mesh network (WMN) is so dynamic due to resource sharing by a majority of mesh nodes and traffic relay cooperation. Conventional field based anycast routing (FAR), which is a hybrid form of geographic routing and back-pressure routing, achieves load balancing, delay reduction, robustness, and scalability in a WMN. However, FAR is vulnerable to a dynamic traffic environment because a tuning parameter, manipulating the reflecting ratio of both schemes, is fixed only for a specific environment. In this paper, we investigate the conditions of the tuning parameter to support dynamic traffic in a WMN. For this purpose, we analyze mathematical forms for the tuning parameter reviewing constant, linear, exponential, log, and Gaussian functions. Numerical analyses and simulations provide a solution to develop advanced FAR which autonomously reacts to dynamic traffic.