Representation of warm conveyor belts in sub-seasonal forecast models and the link to Atlantic-European weather regimes.

Warm conveyor belts (WCBs) are important components of the large-scale flow in the midlatitudes since they transport air from the lower troposphere into the tropopause region and contribute to upper-level ridge building and the formation of blocking anticyclones. These anticyclones make up an important fraction of the variability of the large-scale atmospheric circulation in midlatitudes which is characterised by transient extratropical Rossby waves and stationary patterns. Recent studies indicate that the WCB constitutes an important source and magnifier of forecast uncertainty and errors in numerical weather prediction (NWP) models and might be co-responsible for relatively low forecast skill for certain upper-tropospheric large flow regimes. These flow regimes (also called weather regimes) are of particular importance on sub-seasonal time scales (several weeks to a month in the future) due to their implications for surface weather extremes and socio-economic impacts. [ABSTRACT FROM AUTHOR]