Understanding and Predicting the November 24, 2022, Record-Breaking Jeddah Extreme Rainfall Event

Jeddah, the second-largest city in the Kingdom of Saudi Arabia, experienced an unprecedented 220 mm of rainfall on November 24, 2022. This extreme rainfall, which was four times the climatological monthly mean rainfall for November, resulted in severe flooding and significant damage to infrastructure. This study investigates the underlying physical mechanisms contributing to this extreme event and its predictability using in situ and satellite observations and numerical modeling. Our analysis reveals the event initially developed as a frontal system over the northwest regions of the Red Sea through interactions between cold air from mid-latitudes and warm air from the southeast. It reached Jeddah at 0600 UTC, November 24, accompanied by strong surface convergence, which is typical of winter rainfall in Jeddah. The system was further fueled by persistent moisture intrusion from the Mediterranean and the southern Red Sea, driven by the southeast movement of the Arabian Anticyclone. We evaluated the predictive capability of the Weather Research and Forecasting (WRF) model to forecast this extreme event at different lead times, utilizing a cloud-resolving 1-km configuration. The WRF model, driven by the National Centers for Environmental Prediction operational Global Forecasts, successfully reproduced the extreme rainfall event up to 5 days in advance. Even at a 5-day lead time, the model captured the storm's movement from northwest to southeast and the qualitative spatial distribution of rainfall, consistent with satellite observations and radar reflectivity. Additionally, the predicted distribution of total precipitable water vapor aligned closely with Meteosat brightness temperatures. This demonstrates that the high predictive skill of the WRF model is due to its high-resolution configuration, careful selection of the domain, and physical parameterizations. By addressing both the physical mechanisms and the model's performance, this work provides valuable insights into extreme rainfall forecasting and highlights the potential for mitigating the impacts of such extreme events in the Jeddah region.