19 Investigation of the Relationship between African Easterly Waves and Convection Using Satellite Observations and Reanalysis Data over the East African Highlands

Monday, 18 August 2014
Aviary Ballroom (Catamaran Resort Hotel)
Hilawe Semunegus, NOAA/NESDIS/NCDC, Asheville, NC; and A. Mekonnen

African easterly waves (AEWs) are important components of the Atlantic-African monsoon system during the boreal summer season. AEWs are known to be linked to tropical cyclone (TC)-genesis through their role in providing a preexisting disturbance, a necessary condition for TC-genesis. Past studies have shown that the majority of major hurricanes and nearly half of all Atlantic TCs are associated with AEWs that propagate off the western Africa continent. Studies also noted that most AEWs are initiated over the East African Highlands in association with large-scale convection. However, the mechanisms of convection and AEW initiation and propagation are poorly understood. This study aims to quantitatively measure the AEW-convection relationship. Knowledge of the mechanisms convection and AEW-initiation would help monitoring convective developments that would in turn improve forecasting abilities. With the recognition that hurricanes can have a significant impact on people, property, and local economies, results of this study aim to complement the effort towards North Atlantic hurricane forecasts and thus better inform emergency managers and local officials. We examine convection using the Weather State dataset from the International Satellite Cloud Climatology Project (ISCCP D1) Climate Data Record (CDR) and dynamics using a higher resolution (0.5°x0.5°) Climate Forecast System Reanalysis (CFSR) dataset. The influence of topography, diurnal cycle and environmental conditions (e.g. wind shear, tropical easterly jets and upper tropospheric waves) in the initiation of AEWs is also examined.
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