Case study 02 presentation

13th to 16th August 2012

"An Archetype of AEW"

Authors: Nicolas Chapelon and Jean Philippe Lafore
Contributors: Emmanuel Poan, Doug Parker; Ousmane Ndiaye, ...

This case study illustrates the life cycle, structure and passage over West Africa of a canonical African Easterly Wave (AEW). The drawing of the corresponding WASAs has been largely detailed in Chapter 12 to illustrate the forecaster guide of the WASA-F method.

The reader is invited to analyze this case study by examining in parallel 3 pdf presentations of chronological panels of figures. The present comment is structured in 3 parts associated with the 3 attached presentations respectively, following a downscaling approach. First, we describe the large scale circulation at mid-latitudes, in the equatorial band and in the Sahel band, and point out their relationships. The second part analyzes the synoptic features with a specific emphasis on the moisture field, through the precipitable water (PW) diagnostic. At last, we analyse in details a 2 days period at a 3 hours frequency to focus on the convection diurnal cycle, and on the behaviour of different MCSs associated with the passage of this AEW.