 This is because a pre-existing near-surface disturbance with sufficient spin and convergence is one of the six requirements for tropical cyclogenesis.There appears to be a 15- to 25-day cycle in thunderstorm activity associated with the monsoon trough, which is roughly half the wavelength of the Madden–Julian oscillation, or MJO.This mirrors tropical cyclone genesis near these features, as genesis clusters in 2–3 weeks of activity followed by 2–3 weeks of inactivity.