9A.3 Variability in African Easterly Waves and interactions with the environment for Tropical Cyclogenesis in the Eastern Atlantic

Wednesday, 2 April 2014: 11:00 AM
Garden Ballroom (Town and Country Resort )
Alan Brammer, SUNY, Albany,, NY; and C. Thorncroft
Manuscript (2.2 MB)

A number of studies have highlighted variability in African Easterly Waves (AEWS) with regard to waves that spawn development downstream of the African coast (e.g.. Hopsch et al. 2010, Agudelo et al. 2011).  In this research a wave tracking routine has been developed to create 32 year database of AEW tracks exiting the African coast.  Based on the previous literature a statistical model defining how likely a wave is to develop downstream has been developed.  This allows categorisation of waves upon leaving the coast with regard to their probability of spawning cyclogenesis downstream.  The skill of this model is relatively low with many aspects determining cyclogenesis but it does however allow very unfavourable waves to be identified and then later excluded from the analysis. 

Previous analysis has categorised all developing waves and all non-developing waves. This masks a lot of the detail with regard to non-developing waves that were seemingly favourable for development.  Using the statistical model generated, this research is able to categorise waves into favourable and unfavourable for development.  The favourable category includes most of the developing waves, but also a large number of non-developing waves.  The research will then analyse the evolution and environmental impacts of the favourable but still non-developing waves.  This analysis will reveal much more detail in why waves that are all initially favourable for development experience different outcomes downstream.  Revealing the importance of wave scale processes and interactions with the environment. 

While the research will be largely conducted using a reanalysis dataset for the temporal and spatial continuity.  Results will be confirmed with in situ observations taken from the NASA HS3 field campaign.  Dropsondes were dropped across both the developing pre-Nadine wave and through a saharan air layer outbreak near a non-developing wave.  These in situ observations will confirm the structure and characteristics of the environmental air around the systems. 

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