Tropical upper tropospheric trough
A tropical upper tropospheric trough (TUTT), also known as the mid-oceanic trough, is a trough situated in the 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.
Source: Wikipedia — Tropical upper tropospheric trough (CC BY-SA 4.0)