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Rossby wave packets (RWPs) are one of the dominating midlatitude atmospheric phenomena. A realistic representation of RWPs is essential for a skillful prediction of the day-to-day weather and its extremes. Using an objective RWP tracking technique, this study verifies the representation of RWPs for all models in the Subseasonal to Seasonal (S2S) Prediction Project Database. Consistent with reanalyses, the reforecasts show one RWP every 4 days. The three models with the coarsest grid spacing tend to overestimate the propagation distance due to a negative RWP decay frequency bias over the Atlantic-European sector. A verification of atmospheric blocking suggests that this bias is related to a negative blocking frequency bias in the same region. The biases are reduced in models with finer grid spacing. However, that this bias reduction is not only dependent on the grid spacing highlights the effect of the different representation of key physical processes on RWPs and blocking.

Plain Language Summary Equatorward and poleward perturbations propagating eastward along the fast flowing air currents in the upper troposphere are commonly referred to as Rossby wave packets (RWPs). These packets have been linked to extreme weather events such as intense low-pressure systems, extreme temperatures, and precipitation. Hence, an adequate representation of RWPs in state-of-the-art weather prediction models is desirable to better predict these events. This study is the first to verify the representation of RWPs in a large set of weather prediction models on time scales of up to 28 days. It is shown that fundamental properties such as their climatological frequency of occurrence, their life time, and their mean propagation distance are represented reasonably well. However, models-especially those with a rather coarse horizontal grid spacing-struggle to adequately represent the decay of these waves in the Atlantic/European sector. Instead of decaying over the eastern North Atlantic, RWPs propagate into far eastern Europe likely due to an underestimation of the occurrence frequency of long-lasting and stationary high-pressure systems.