Seasonal Predictability of Baroclinic Waves Establishes Pathway Toward Predicting Extratropical Extremes

Abstract:

Midlatitude baroclinic waves drive extratropical weather and climate extremes, but the wave predictability beyond 2 weeks has been deemed low. Here we analyze a large initial-value ensemble simulation forced by the observed sea surface temperature (SST) and illustrate that year-to-year variations of baroclinic waves are predictable on a seasonal scale. The regions with high potentials of skillful predictions include the subtropics and a midlatitude region extending from North America to the North Atlantic. By filtering out unforced variability, the large ensemble simulation lends insights into the SST forcings of baroclinic wave activity. A regression analysis delineates well-known and unfamiliar wave responses to SST forcings, pointing to SST-related predictability of baroclinic wave activity. We further show that the predictability of baroclinic waves can be harvested using a newly developed dynamical prediction system. These findings help to understand the seasonal predictability of weather processes and pave the way for extending the long-range prediction of extratropical weather extremes.