The atmospheric wave pattern that causes large north–south meanders in the jet stream is a Rossby wave.
Rossby waves are large-scale planetary waves caused mainly by Earth’s rotation and the change in the Coriolis effect with latitude. In the atmosphere, they commonly appear as broad ridges and troughs in the westerly flow of the mid-latitude jet stream.
These waves move more slowly than the air flowing through them and can steer weather systems for days or weeks. A ridge generally favors sinking air and often calmer or warmer conditions, while a trough favors rising air and can help bring cooler air, clouds, and storms. Very large-amplitude waves can produce persistent weather patterns.
The waves are named after Swedish-American meteorologist Carl-Gustaf Rossby, who explained their dynamics in the 1930s. Rossby waves also occur in oceans. They should not be confused with ordinary small ripples in wind or with Kelvin waves, which have different dynamics and geographic behavior.