A tropical upper tropospheric trough (TUTT), also known as the mid-oceanic trough, is a trough situated in upper-level (at about 200 hPa) tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper level anticyclone. TUTTs are different from mid-latitude troughs in the sense that they are maintained by subsidence warming near the tropopause which balances radiational cooling. When strong, they can present a significant vertical wind shear to the tropics and subdue tropical cyclogenesis. When upper cold lows break off from their base, they tend to retrograde and force the development, or enhance, surface troughs and tropical waves to their east. Under special circumstances, they can induce thunderstorm activity and lead to the formation of tropical cyclones.