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Abstract

Extratropical cyclones dictate the weather in the mid-latitudes. Cyclones intensify in regions of high baroclinicity and their typical path of travel (called storm tracks) is with, and on the poleward flank of, the mid-latitude jet stream. Storm track-associated latent heating alters the environmental baroclinicity, affecting the jet through the thermal wind balance. The environmental baroclinicity also affects the preferred type of wave breaking, which pushes the jet poleward (anti-cyclonic wave breaking) or maintains a zonal jet profile (cyclonic wave breaking). Therefore, latent heating appears to be a feedback to latitudinal storm track and jet shifts.However, the sign of this diabatic feedback is not known.We show that the feedback is conditional on the jet configuration. We trace the latent heating contribution to baroclinicity relative to large-scale atmospheric features and obtain relevant aggregates along zonally asymmetric storm tracks. The persistency of the jet in its anomalous locations defines the monthly and seasonal mean mid-latitude weather. Seasonal forecast models underestimate the persistency of latitudinal jet shifts, known as the signal to noise paradox, possibly due to the models' poor representation of moisture. In a warming climate, the atmospheric moisture content will increase and diabatic effects are therefore expected to become increasingly important and thus crucial to the reliability of climate projections.