Shortwave Trough
A shortwave trough is a small-scale disturbance in the upper-level wind flow — a localized area of cyclonic curvature in the jet stream that moves faster than the larger-scale pressure pattern. Shortwave troughs are primary triggers for surface weather development, including thunderstorms and precipitation.
How Shortwave Troughs Generate Weather
As a shortwave trough moves through the jet stream, it creates upward motion on its downstream (east) side. This divergence in the upper atmosphere draws air upward from below, reducing surface pressure and creating surface low-pressure development. Coupled with moisture and instability at low levels, this lifting mechanism triggers convection, precipitation, and potentially severe weather.
Aviation Significance
- Shortwave trough passage is a reliable trigger for convective development
- Watch for new surface lows developing ahead of shortwave troughs — rapid weather development possible
- Embedded shortwave troughs can produce unexpected convection within a general cloud mass
- GFA synoptic charts and upper air analyses depict shortwave troughs
On the TC Written Exam
Shortwave troughs appear in upper-level meteorology and weather development sections of CPL exams. Know: they trigger weather by creating upward motion; they move within the larger flow; they are visible on upper-level charts.
Related Terms
See also: Trough, Jet Stream, Thunderstorm.