9A.1 Evolution of long-lived African Easterly Waves (2008

9A.1

Evolution of long-lived African Easterly Waves

Anantha R. Aiyyer, North Carolina State University, Raleigh, NC

The accumulated evidence in the literature suggests that tropical cyclones(TCs)

evolve from pre-existing cyclonic disturbances. In the Atlantic, westward

moving, African easterly waves (AEWs) are usually implicated as being the

precursors to hurricanes. It has been suggested that a large fraction of

Atlantic tropical cyclones originate from AEWs. However, there remain several

gaps in our understanding of the structure, propagation and transformation

of these disturbances into tropical cyclones.

In this study we examine the detailed structure of AEWS, and the role of the

environmental wave-guide, and disturbance scale convection in sustaining them

once they exit the source region in West Africa. To this end, we examine

several cases of long-lived AEWs and document their evolution and eventual

transformation into TCs. The methodology used is a combination of Observations

based analysis and numerical simulations.