Tropical Upper-Tropospheric Troughs and Tropical Cyclones: Past, Present, and Future

The Tropical Upper-Tropospheric Trough (TUTT) is a seasonal atmospheric phenomenon that occurs over the world's subtropical oceans. Concentrated areas of vorticity often develop in these troughs that persist as upper-tropospheric cyclones, or “TUTT cells.” Since the early years of atmospheric streamline analyses over the tropical and subtropical oceans, the TUTT has been observed to play an important role in the synoptic and large-scale interactions between the tropics and midlatitudes. Tropical cyclones (TCs) are routinely influenced by upper-tropospheric phenomena, which have been shown to affect TC development and behavior, particularly TC intensity change. As we seek to advance our understanding of TCs and to improve TC track and intensity forecasting in an era of high-resolution, high-quality global modeling, a review of over 40 years of observational and theoretical studies of TUTTs and TUTT cells (TUTTcs) is appropriate.

TUTTc characteristics and dynamics are discussed, with an emphasis on their interactions with TCs. The effects of TUTTcs on TC intensity change remain poorly understood, especially with respect to the relationships between their structures and TC asymmetries. Quantitative analyses of TC-TUTTc interaction remain elusive, and present understanding of TUTTc influences on TCs is mainly subjective and often anecdotal. Yet, advancement in TC intensity forecasting requires a quantification of TUTTcs and their influence on TCs. Development of an objective TUTT cell tracking method is currently underway, which will enable statistical stratifications of TUTTc structure and TC-TUTT interactions. Preliminary results of the developmental TUTT cell tracking methodology will be presented.