On the Relationship between African Easterly Wave Structures and the Probability of Tropical Cyclogenesis in the Tropical Atlantic

Abstract:

This talk will provide an overview of the African easterly wave (AEW) structures that occured during the 3 consecutive summers of the HS3 observing campaign: 2012-2014. An objective metric will be presented and exploited to define which AEWs were favorable for tropical cyclogenesis and those which were not. A more detailed analysis, combining model outputs and observations, will be presented that compares notable developing AEWs (e.g. Nadine and Edouard) and their preceding non-developing AEWs.Emphasis will be given to the evolving dynamical AEW structures at low-levels as they move from the continent into the Atlantic. It will be shown that there is a short "window" when the low-level monsoon westerly flow in the eastern Atlantic establishes a west-to-east flow under the mid-level trough making the trough vulnerable to advection of dry-air from ahead of the trough. It will be shown that if their is relatively moist air ahead at low-levels the probability of tropical cyclogenesis increases even with a west-to-east flow under the trough. The implications of this work for future targeting efforts will be discussed.