What is a tropical upper tropospheric trough (TUTT)?

TUTTs can form in tropical regions of the Atlantic, Pacific and Indian Oceans. While they can occur during any time of the year, these features are more common during the warmer months.

A Tropical Upper Tropospheric Trough (TUTT) is an elongated region of low pressure in the upper atmosphere that can form when there is a significant gradient of sea temperatures or sudden changes in pressures or wind patterns.

TUTTs can form in any tropical region of the Atlantic, Pacific and Indian Oceans and are primarily known as hurricane killers.

These areas of low pressure can create strong upper-level winds that disrupt the vertical structure of a tropical cyclone, lead to dry air intrusion and cause widespread stability.

While they can occur during any time of the year, these features are more common during the warmer months.


During the 2021 hurricane season, a large TUTT established itself in the southwest Atlantic and acted as a protective barrier for much of the East Coast.

The Bahamas, eastern Florida and Carolinas were free from a direct strike, with more powerful cyclones occurring outside of its realm of influence.

Wind shear is greatest on the southern and eastern sides of a TUTT, which are typically over or near what is known as hurricane alley.

The overall frequency of these cold-core features varies from year to year and can be unpredictable.

An average season in the Atlantic basin produces 14 named storms, seven hurricanes and three major cyclones, but the intensity and overall amount of formations can be reduced when significant TUTT features are in place. 

A large-scale TUTT in the Atlantic in 2022 caused a historically inactive period in the tropics. August finished without a named tropical cyclone for only the second time in the modern satellite era.


In unique cases, a TUTT can help to enhance a tropical cyclone’s outflow, but the storm system and the upper-level feature must work in tandem, or else it’ll become sheared.

TUTTs tend to be more common in the Atlantic during El Niño events versus in La Niñas.

During periods of enhanced instability, multiple TUTTs can coexist in a basin, leading to extremely hostile conditions for significant tropical organization.