Convective Adjustment, Gravity Waves and Diurnal Regulation of Tropical Cyclogenesis

Here we show that a key precursor of tropical cyclogenesis is the episodic burst of deep convection over a vorticity-rich environment preconditioned by tropical waves which is followed by quasi-periodic cycles of gravity wave-cloud-radiative feedbacks. The convective adjustment and wave-cloud interaction process has an intrinsic time scale of 12-36 h, which makes it more readily to oscillate with and be further regulated by the diurnal cycle of solar insolation. In particular, the lack of solar radiation during nighttime helps the destabilization and moistening of the troposphere which is conducive to enhanced moist convection and tropical cyclogenesis. We will present this quasi-periodic cycle of convective adjustment, gravity waves and diurnal regulation during genesis of a few selected tropical cyclones that include Hurricanes Dolly (2008), Karl (2010), Edouard (2014) and Super Typhoons Megi (2010) and Neparket (2016).