Mesoscale Convective Systems Modulated by Convectively Coupled Equatorial Waves

Mesoscale convective systems (MCSs) produce over 50% of tropical precipitation and account for the majority of extreme rainfall and flooding events. MCSs are considered the building blocks of larger-scale convectively coupled equatorial waves (CCEWs). While CCEWs can provide favorable environments for convection, how CCEWs can systematically impact organized convection and thereby MCS characteristics is less clear. We examine this question by analyzing a global MCS tracking data set. During the active phase of CCEWs, MCS frequency increases and MCSs rain harder, produce more lifetime total rain, and grow larger in size. The probability of extreme MCSs also elevates. These changes are most pronounced when MCSs are associated with Kelvin waves and tropical depression-type waves while less so with the Madden-Julian Oscillation. These results can be benchmarks to improve model representation of MCS interactions with large-scale circulations and can be leveraged for operational forecasts of high-impact MCSs at extended lead times.

Automated summary

Mesoscale convective systems (MCSs) contribute significantly to tropical precipitation and extreme rainfall events. The impact of convectively coupled equatorial waves (CCEWs) on organized convection and MCS characteristics is examined using global tracking data. During the active phase of CCEWs, MCSs exhibit increased frequency, intensity, size, and probability of extreme events, particularly when associated with Kelvin waves and tropical depression-type waves.