Seasonal Variability in Thermodynamic Conditions Preceding Heavy Rainfall in the Free State, South Africa

I. M. Schoeman* and A. van den Heever

North-West University, Potchefstroom Campus, South Africa

Forecasting heavy rainfall in early austral summer (October to December) requires different techniques than in late austral summer (January to March). Hence, threshold values associated with heavy rainfall will also change over this period.

The aim of this presentation is to identify the thermodynamic variables that occur in conjunction with heavy rainfall events in the Free State province in South Africa and to determine the threshold values of these variables before heavy rainfall. The process involves establishing a baseline mean state of the applicable thermodynamic variables for each month during the study period and then compare this against the thermodynamic variable means observed on the specific days that met the criteria for heavy rainfall.

Improving understanding of thermodynamics in this data-scarce region—often called South Africa’s breadbasket—could strengthen early warning systems. Earlier alerts for heavy rainfall would help mitigate potential impacts. This study is conducted using an event set comprising over 30 years of weather station and ERA5 data.

Keywords: Seasonality, Thermodynamics, Heavy rainfall.

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