Far above the weather we feel at the surface, enormous waves are constantly shaping the atmosphere. These waves, known as Rossby waves, help steer the jet stream and guide the pathways of cold surges, storms, heavy rainfall, and other high-impact weather events. When Rossby waves grow large enough, they can overturn and “break,” much like ocean waves.
Rossby wave breaking is one of the large-scale clues that weather and climate models use, directly or indirectly, to identify environments where extreme weather is more likely. If a model gets the frequency, strength, or location of these breaking events wrong, it may also distort the atmospheric signals linked to high-impact weather. As society increasingly relies on models to understand how extremes may change in a warming climate, getting these large-scale signals right becomes even more important.
To test whether this problem appears in forecasts, scientists from Florida State University examined Rossby wave breaking in two major global models, the European Centre for Medium-Range Weather Forecasts (ECMWF) model and the U.S. National Centers for Environmental Prediction (NCEP) model. They compared the forecast world with the real world, using each model's analysis as its best estimate of the actual atmosphere. They then tracked different types of wave breaking across several key regions and followed how the errors changed as the forecasts moved farther away from their initial conditions.
The results reveal clear and systematic drifts. In one Pacific region dominated by cyclonic wave breaking, for example, the forecast showed a drift of about −20.8% over 15 days.
“In plain terms, the model increasingly weakened this type of breaking as the forecast progressed, meaning that the broader atmospheric pattern associated with high-impact weather may become too weak in the forecast world compared with the real world.” Said Dr. Shuhang Xue, the lead author of the study published in Advances in Atmospheric Sciences .
The key to understanding these errors lies in the jet stream. Previous idealized studies have shown that wind shear near the jet can strongly influence how Rossby waves break. The newly published study supports this idea. Part of the forecast error may come from how models represent the background shear around the jet. When that shear is biased, the jet structure is distorted, and the model may favor the wrong type, strength, or location of wave breaking.
This also connects forecast errors to larger climate variability. Major climate modes—including the El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) pattern—can reshape the jet stream and alter the shear environment in which Rossby waves grow and break. A bias in jet shear can therefore echo through the whole forecast chain: from climate modes, to jet structure, to Rossby wave breaking, and finally to the large-scale signals used to anticipate high-impact weather.
“Our study shows that Rossby wave breaking errors are not random technical details, but systematic forecast drifts that vary by region and breaking type.” Said Xue. In this sense, misjudged wave breaking is a measurable pathway through which models may weaken or distort the atmospheric signals used to anticipate extreme weather.
The next step, according to Xue, is to use this dynamical link to improve forecast diagnosis and correction, so that models can better capture the atmospheric patterns that shape high-impact weather risk.
Advances in Atmospheric Sciences
Systematic Drifts of Rossby Wave Breaking in Medium-Range Forecasts over the Northern Hemisphere Cold Season
27-Jun-2026