The role of AR-like moisture plumes in the October 2024 Valencia precipitation event and other western Mediterranean extremes

On 29 October 2024, an extreme precipitation event affected eastern Spain, triggered by a cut-off low, with daily rainfall totals exceeding annual climatological values in several locations. The province of Valencia was particularly impacted, where widespread accumulations surpassed 300 mm and local maxima reached up to 771 mm. Given the magnitude of the event, its dynamical and thermodynamical drivers, as well as the potential influence of climate change, have been the subject of extensive investigation. Several media reports and recent studies (Campos et al., 2025) have highlighted the possible role of an upper-level tropospheric moisture plume resembling an atmospheric river (hereafter, AR-like structure) connecting the Mediterranean region with the tropical Atlantic via North Africa, suggesting a potential contribution to the event’s intensification. However, the quantitative contribution of this structure to the observed precipitation remains unclear.

To address this question, we employ the WRF with Water Vapor Tracers (WRF-WVTs) model, which enables tracking moisture from predefined source regions to precipitation while fully resolving the event dynamics. Our results indicate that moisture evaporated from the Mediterranean Sea constitutes the dominant contribution, whereas moisture associated with the AR-like structure accounts for approximately 20-30% of the total precipitation. To further assess the role of this remote moisture transport, we introduce a methodology to quantify its indirect impact via enhanced latent heat release and the associated increase in atmospheric instability. This methodology is further applied to several additional events in the western Mediterranean characterized by the coexistence of a cut-off low and an AR-like structure producing substantial precipitation. Preliminary results indicate that this indirect mechanism is considerably more important than the direct moisture contribution, highlighting the key role of mid-tropospheric moisture supplied by these structures in intensifying such events.

Campos, D. A., Grayson, K., Saurral, R. I., Beyer, S., John, A., Olmo, M., and Doblas-Reyes, F.: The October 2024 Extreme Precipitation Event over Valencia: Storyline Attribution of the Synoptic-Scale Thermodynamic Drivers, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-5929, 2025.