Land-based High Frequency (HF) surface wave radars have become an effective tool for sensing currents, winds and waves, and many types of HF radars are in operation around the world. Being different from land-based HF radars, this paper proposes a concept of shore-to-air bistatic HF radar for ocean observation. The configuration of shore-to-air bistatic HF radar is introduced in the paper, and the first-order scattering model is also presented. The paper studies and analyzes the average scattered cross section per unit area at different operating frequencies and with various wind speeds via simulation. Simulations demonstrate that the average scattered cross section per unit area varies along with frequency, wind speed and scattering direction. The proposed model will help develop shore-to-air bistatic HF radars for ocean observation.