Influence of Storm-Environment Interactions on Tropical Cyclone Development from a Train of African Easterly Waves

More than half of all tropical cyclones (TCs) over the North Atlantic basin develop from westward-propagating African easterly waves (AEWs). As these AEWs emerge from Africa over the eastern North Atlantic basin, some quickly develop into TCs within a few days, while others take longer to develop and some will not develop at all. The aim of this presentation is to study a train of four AEWs that emerged from Africa in late August through early September 2010. These four AEWs developed into TCs Danielle, Earl, Fiona, and Gaston. The train of AEWs is of interest because the AEWs interacted with the synoptic-scale environment, which influenced the life cycle of the disturbances themselves. For instance, while Danielle and Earl formed quickly and eventually intensified to major hurricanes, Fiona and Gaston’s development was delayed and neither system reached hurricane intensity.

Emerging results suggest that the environment over the North Atlantic basin became progressively drier in the wake of each tropical system, making it increasingly difficult for development to occur. The drying occurred as the synoptic flow pattern became increasingly meridional in the wake of TCs Danielle and Earl. The ability of numerical modeling systems to predict TC genesis in the medium-range in situations where a train of disturbances are located in the tropical North Atlantic hinges on the model prediction of the storm’s interaction with the synoptic-scale flow. Ensemble forecasts from the TIGGE archive will be examined to determine factors that distinguish development from non-development in the ensemble forecast, such as differences in storm environment and storm structure.