Environmental conditions and structure of the West African and Eastern Tropical Atlantic squall lines

Abstract

The environmental conditions in advance of three West African disturbance lines and three Eastern Atlantic squall lines are examined as is the modification of the environment during the passage of such storms over a site. A comparison with other tropical squall lines observed over Venezuela is made. A model of the relative airflow within a West African disturbance line is presented and some aspects of storm movement are considered. The hydraulic jump analogy and a density current model are applied to the convective systems and the results obtained are compared with observations. The hydraulic jump analogy gives reasonable predictions for the storms' speeds and the density current model results show that for the West African disturbance lines, as well as the Venezuelan storms, a close relationship exists between the storm speed and the speed of the density current. As this relationship is not observed in the Eastern Atlantic squall lines, it appears that the density current model is not applicable to convective systems occurring over the ocean.