whereby the sides of interfering body 6 slope inwards from the base of interfering body 6 is a novel feature of the current invention when air flows through sensor 2 the inward sloping of the walls of interfering body 6 generates a pattern of airflow which characteristically includes a turbulent boundary layer around the base of interfering body 6 as will be well known to one familiar with the art the interfering body of existing differential pressure airflow sensors is designed so as to facilitate laminar airflow through the sensor and specifically avoid turbulence as such the sides of the interfering body are essentially parallel to each other a design feature that is aerodynamically advantageous for the purpose of minimizing turbulence both within and outside of the boundary layer of airflow a point of novelty of the current invention lies in fashioning interfering body 6 with sloping that is non parallel or converging sides so as to deliberately encourage turbulent airflow within sensor 2 this design feature results in an area of turbulent airflow within the boundary layer at the base of interfering body 6 as water precipitation is enhanced in turbulent as opposed to laminar boundary layers droplets of water tend to precipitate at the base of interfering body 6 rather than in pressure.