Tropical Wave Interactions: From Dynamics to Numerical Prediction

Host: Michael Bell

Presenter: Quinton Lawton – NSF National Center for Atmospheric Research 

Location: ATS 101

The accurate representation of atmospheric waves in the tropics remains a key operational challenge, in part because these systems can have significant local and downstream impacts. Recent research has also shown that interactions between tropical waves can promote tropical cyclone formation and trigger localized extreme rainfall. However, numerical models often struggle to simulate these waves accurately, and their ability to represent wave interactions is poorly understood.

In this talk, I discuss recent advances in our understanding of the dynamics, interactions, and predictability of two types of tropical waves: easterly waves (EWs) and convectively coupled Kelvin waves (CCKWs). I begin by highlighting how object-tracking techniques can be used to quantify the variability and dynamics of these waves, as well as the processes linking their interactions to extreme weather events. I then present ongoing work assessing the fidelity of numerical models in simulating tropical waves and their interactions. These include physics-based operational models, the Artificial Intelligence/Integrated Forecasting System (AIFS), and the Model for Prediction Across Scales – Atmosphere (MPAS-A). Our results demonstrate that the physics-based models produce CCKWs that are weaker and propagate faster than in satellite-based observations, likely due to deficiencies in simulating their convective coupling. In contrast, AIFS shows a remarkable ability to simulate CCKWs and EWs, outperforming the other models. Nevertheless, all of the models routinely fail to represent CCKW–EW interactions. These findings underscore how persistent challenges in tropical wave forecasting may hinder our ability to predict extreme weather events, highlighting a need for additional research and model development.