The person who first identified them, Carl-Gustaf Arvid Rossby, in 1939, noticed that warm air moving north would shift towards the east and that cool air moving south would move eastward.
Subsequently the southern hemisphere the waves still move to the east, due to the Coriolis effect, just the direction of the warm and cool are opposite.
Without knowing the term Rossby Waves, you are probably aware of terms like High-Pressure Ridge, or Low-Pressure Trough.
It is a delight for TV and streaming video meteorologist to mention as they can, put on a show, on a large map.
Living in the 30–60-degree latitudes, is where you are most likely to see weather change almost every day.
What you are seeing is a part of Rossby Waves.
At any given time, there can be zero waves to more than 6 around each of the northern and southern poles.
Due to the polar cooling ranges and the equatorial warning areas, Rossby Waves tend to stay in the 30-60 deg north and south latitudes. This is where the strongest flows of warm air masses will move towards the polls and the strongest flows of cool air masses move towards the equators.
Our spinning planet will cause Rossby Waves in the atmosphere but can also be seen in oceanic conditions. Rossby waves are partially the cause of the currents in the oceans. Taken a step further such phenomenon can be witnessed on other planetary fluid masses.
Some important observations of Rossby waves, in the sky are.
- Upper-level clouds shifting northeastward, while the lower-level clouds are moving in a different direction. (denotes an approaching low-pressure system.) Subsequentially upper-level clouds shifting to the south east denotes an approaching High-pressure system.
- Fast paced back winds, in opposition to current trends can be the influence of upper winds, and denote an approaching change, (this opposition wind can be utilized to note the approach as in the cloud movement by reversing that opposition wind at the surface and noting the direction as the forbearance to the incoming system.)
- Lack of or sluggish cloud movement or wind activity tells you that systems are not going to change soon (hours to a day)