A communications node for transmitting and receiving beyond line of sight (BLOS) communications through an evaporation duct (ED) environment proximate to a body of water (e.g., coastal, littoral) models environmental conditions (e.g., duct heights) based on current climate data for the ED environment. Based on the modelled ED conditions, the node generates signal propagation models for each of a set of possible transmitting frequencies (e.g., likely signal loss, transmission range). Based on the most current ED signal propagation model, the node selects the optimal transmission frequency for BLOS communications through the evaporation duct.