Training (meteorology)

In meteorology, training denotes repeated areas of rain, typically associated with thunderstorms, that move over the same region in a relatively short period. Training thunderstorms are capable of producing excessive rainfall totals, often causing flash flooding.¹ The name training is derived from how a train and its cars travel along a track (moving along a single path), without the track moving.²

Showers and thunderstorms along thunderstorm trains usually develop in one area of stationary instability, and are advanced along a single path by prevailing winds. Additional showers and storms can also develop when the gust front from a storm collides with warmer air outside of the storm. The exact process repeats in the new storms until overall conditions in the surrounding atmosphere become too stable to support thunderstorm activity. Showers and storms can also develop along stationary fronts, and winds move them down the front. The showers that often accompany thunderstorms are usually thunderstorms that are not entirely developed.

A series of storms continually moving over the same area, dumping heavy rains, can cause flash flooding.¹ Each storm usually produces heavy rain, and after a significant amount of rain falls from the storms which have moved over the same area, flooding occurs.

Thunderstorm training is used to refer specifically to training occurring with thunderstorms. It forms when storms tend to back build. This type of training can quickly cause flash flooding, especially if the thunderstorms are strong.

A linear rainband is an elongated, narrow area of precipitation in which rain clouds or thunderstorms are organized in a line. Linear rainbands may occur along fronts, convergence zones, tropical cyclones, or other regions where moist air is forced to rise. When the individual rain cells within a linear rainband repeatedly move over the same area, the process is known as training.

Linear rainbands can produce heavy rainfall over a relatively small area, especially when the band remains nearly stationary or when new convective cells continuously form on the upstream side of the band. In such cases, rainfall totals can increase rapidly and may lead to flash flooding, river flooding, landslides, or other rainfall-related hazards.

In Japan, a similar phenomenon is commonly referred to as a senjo-kousuitai or linear precipitation zone, in which developed cumulonimbus clouds form a line and bring intense rainfall to the same area for several hours.