In this chapter, we examine the wide-variety of synoptic and mesoscale weather systems that affect the tropics, including, tropical easterly waves, upper tropospheric troughs, subtropical cyclones, and monsoon depressions. Extratropical interactions, such as those caused by Rossby wave trains and the MJO, are examined. This chapter presents a review of thunderstorms and lightning. The structure, formation mechanisms, and hazards of mesoscale convective systems are examined. The distribution of lightning globally and within mesoscale systems is examined. Mesoscale and local circulations, such as sea-breezes, are explored. The final section focuses on supercells, tornadoes, and waterspouts.