On the Non-development of a Strong African Easterly Wave: Investigating Ensemble Forecasts and In-situ Observations.

The evolution of a strong African easterly wave trough and the embedded mesoscale vortex is analysed with respect to its transition over the west African coast and the potential for tropical cyclogenesis. The presentation will discuss the evolution of the African Easterly Wave and its synoptic history over West Africa. Dropsondes from the HS3 field campaign are utilised to diagnose the structure of the vortex and environment interactions occurring over the eastern Atlantic. Finally, ensemble forecasts from global models are utilised to assess the differences between developing and non-developing outcomes of the single case.

This analysis will highlight the role of dry air entrainment over the eastern Atlantic leading to the lack of convection and a potential negative feedback cycle that can occur. Observations, re-analysis and forecasts highlight how small differences in the vortex-environment structure can influence the entrainment of the dry air and the resulting evolution of the disturbance.