TUTT explained, from NOAA:

A "TUTT" is a Tropical Upper Tropospheric Trough. A TUTT low is a TUTT that has completely cut-off. TUTT lows are more commonly known in the Western Hemisphere as an "upper cold low". TUTTs are different than mid-latitude troughs in that they are maintained by subsidence warming near the tropopause which balances radiational cooling. TUTTs are important for tropical cyclone forecasting as they can force large amounts of harmful vertical wind shear over tropical disturbances and tropical cyclones. There are also suggestions that TUTTs can assist tropical cyclone genesis and intensification by providing additional forced ascent near the storm center and/or by allowing for an efficient outflow channel in the upper troposphere.

Hope that helps...