ABSTRACT
Shearing at the boundary between the lower, humid and upper, dry airmasses, leads to the development of waves in the base of the easterlies. From these waves may originate line squalls which may travel across West Africa from east to west with the waves as they ‘ripple’ along the airmass boundary. The shearing effect on the boundary of contrasting fluid mediums moving by each other, as can be observed as the wind blows over water surfaces, creates wave motions. The release of latent heat in the development of such waves in the atmosphere may aid their growth. Bands of often heavy and prolonged rain, some 160 km long west to east, 50 to 80 km north to south, associated with the perturbations, travel with the southwesterly airflow across West Africa from the Guinea coast, diminishing in significance as the depth of humid air decreases. The lines of squalls generated in the east may traverse the whole West African region.
