“…extensively The two band-periods between 3 and 5 days correspond to studied over West Africa and the tropical Atlantic between the well-known easterly waves travelling over West Africa 5øN and 20øN during northern summer (Carlsbn, 1969a, b, and the tropical Atlantic. The band-period covering 6-9 Burpee, 1972, 1975, Reed et al, 1977, 1988a. days was also detected for different variables resulting from Typically they have a wavelength of about 2500-3000 kin, observations in meteorological stations, from a period of 3-5 days and propagate westward with a phase radiosounding, and from other analysis datasets (see velocity of about 7-8 degree longitude per day.…”