Toward Improving Tropical Rainfall Forecast Skill: Do Equatorial Waves Matter?

Despite decades of research on the roles of moist convective processes in large-scale tropical dynamics, tropical forecast skill in operational models is still deficient, even at short lead times. A number of studies indicate that convective parameterizations play a major role in how moist convective processes are coupled to the large-scale flow; thus, they appear to be the main reason for why weather and climate models have a difficult time representing equatorial waves such as the Madden-Julian Oscillation and Kelvin waves. This study focuses on the relationship between the lead time evolution of tropical rainfall forecast skill in operational models and their ability to simulate synoptic-to-planetary scale tropical waves. To address this question, we test two convective schemes known to improve tropical convective variability, namely a scale-aware and a super-parametrized scheme. Results so far suggests that the inherent deterministic predictability associated with equatorial waves helps improve tropical rainfall skill at lead times from 1-6 days.