Predictability of Tropical Cyclqgenesis in Different Synoptic-Scale Flow Regimes

The predictability of tropical cyclogenesis is evaluated over the North Atlantic for different genesis pathways using the Global Ensemble Forecasting System (GEFS) Reforecast Version-2. A previous study has defined five genesis pathways based on the low-level baroclinity and upper-level forcing of the genesis environmental state: non-baroclinic, low-level baroclinic, trough-induced, weak tropical-transition (TT) and strong TT pathways. It was found that genesis associated with stronger upper-level forcing (strong TT and weak TT pathways) has lower predictability than that associated with weak upper-level forcing (non-baroclinic and low-level baroclinic pathways). The different genesis predictability can be explained by the different predictability of deep tropospheric vertical shear and mid-level humidity in the vicinity of genesis.