Aviation weather provided the starting point for RAL's research work. Within the aviation application area, our current research emphases are: in–flight icing; snowfall and freezing precipitation; convective storm nowcasting and forecasting; atmospheric turbulence; numerical weather prediction; remote sensing; data assimilation; precipitation physics; ceiling and visibility; oceanic weather; verification methods; and advanced dissemination technology to users on the ground and in the air. Development of useful aviation applications requires a strong connection between our work and the needs of aviators. End–user requirements are considered at each step along the development path. Our work tends to be heavily oriented toward real–time operational systems and this focus leads to an emphasis on algorithm development, specialized graphical displays, systems engineering, operational demonstrations, and the associated scientific validations and user–oriented evaluations.