Summary From the standpoint of practical forecasting the simplest method of attack on the problem of cyclogenesis in the tropical Atlantic is through katallobaric waves, which are apparently generated along the tropical front between the SW monsoon and the NE trade. Waves initiated in the Cape Verde region move within the NE and E trade toward the Antilles with a frequency of one about every 3 or 4 days. They are usually comparatively stable but are almost invariably attended by a moderate rise in the Ts inversion level. Available data are not entirely conclusive concerning the transition from stable to unstable waves but it apparently depends upon the extent of the destruction of the Ts inversion.