The understanding and prediction of high impact weather over West Africa

Project description / Motivation
Deep convection in the tropics is the engine-room of the global climate, communicating energy, momentum and water between the major climatic systems (earth, atmosphere and ocean). Convection is really the driver of the tropical circulation, and tropical-extratropical transitions are important for weather prediction all over the globe.
Convective clouds also deliver heavy rainfall and winds, and are the drivers of much of the severe weather experienced in the tropics. High impact weather (HIW) systems, such as heavy precipitation from thunderstorms that can lead to flooding, and high winds that may pose a threat to fisherman, are often linked to waves in the mid-troposphere over West Africa; so called African easterly waves. For instance, the Gulf of Guinea and adjacent coastal regions experience some of the most severe thunderstorms on the Earth, which pose a threat to local fisherman, shipping in the region, and the oil and gas industry. Over the Gulf of Guinea, the weather conditions can change quickly within an hour from seemingly calm conditions to strong winds, heavy rain and high waves.
Despite their importance, these clouds remain very poorly predicted, and their feedback on the climate system is one of the biggest uncertainties in weather and climate prediction. The cloud systems are able to self-organise, through fluid-dynamical interactions, so that elements on the scale of 10km can organise into systems lasting many hours or days, on scales of 100s of kilometres. This project aims to investigate the dynamics and predictability of these organised thunderstorm complexes, which are called mesoscale-convective systems (MCSs) or squall lines, over West Africa and the Gulf of Guinea.
The project will use observations, numerical model simulations and mathematical theory to advance our understanding of these storms and how they interact with the circulation systems of the Earth’s tropics. We aim to test and develop mathematical models for the ways in which latent heating in clouds influences atmospheric circulation, on scales from a few kilometres (individual thunderstorms) up to a few thousand kilometres (e.g. waves, cyclones and monsoons).
The project may make use of a variety of theoretical and numerical methods, and may include efforts to advance already existing methods to objectively identify (e.g. Hoang et al. 2017) and then track MCSs and squall lines (e.g. Weller et al. 2017). These methods will be adapted for squall lines in the Gulf of Guinea and across West Africa so they can be used to track features in Met Office forecast products at different horizontal resolutions in the future. Once the squall lines have been objectively identified over coastal and oceanic regions we will investigate why and how they form, their evolution and what they have in common with land forming squall lines over the land regions of West Africa. This investigation will be based on satellite data from geostationary and polar orbiting satellites, analysis and reanalysis datasets from the European Centre of Medium range Weather Forecast (ECMWF) as well as global and convection-permitting weather forecasts from the Met Office Unified Model (MetUM).
Another aim of the project will be is to advance our theoretical understanding of the dynamics of tropical convective clouds and their environment, and thus to improve numerical weather prediction of squall events in the Gulf of Guinea, resulting in more accurate prediction and longer lead times for operational early warning systems. For example, we will also have the opportunity to develop advanced theoretical tools to characterise the cascades of energy and enstrophy from the convective scale (a few km) up to the regional scales.
Scientific literature on these HIW events is limited, despite the significant impact on human lives and livelihoods. This project is a real opportunity to contribute to fundamental understanding of storm genesis, lifecycle and physical impacts in a region that has had little attention to date.