Tornadic Event in Portugal in March 2024: Synoptic environment and Forecasting

On 28 March 2024, a significant convective weather event impacted Portugal, producing multiple reports of severe wind, including conformed tornadoes, one of them ocurring in the vicinity of Lisbon. This study provides a concise analysis of the synoptic and mesoscale conditions that led to the development of these phenomena. The environment was characterized by an unstable air mass, supported by favorable thermodynamic and dynamic parameters, such as elevated CAPE and storm-relative helicity, supporting the potential for tornadogenesis.Deterministic and ensemble numerical weather prediction (NWP) products from ECMWF and AROME models were used to assess precipitation patterns and wind gust forecasts. While ensemble outputs suggested potential for localized high-impact weather, there was substantial uncertainty regarding the intensity and spatial distribution of precipitation and maximum wind gusts. Mesoscale forecast products further supported the likelihood of severeweather, as predicted by forecasters in advance.We also present insights into the operational forecasting process at the time, such as weather bulletins and experimental nowcasting guidance for convective storms. Observations confirmed the occurrence of tornadoes in the Tagus estuary (close to Lisbon) and in Benaciate (Algarve), along with intense convective wind gusts in other locations. These observations aligned with the earlier model indications and operational forecasts, validating the usefulness of high-resolution ensemble forecasting and real-time convective diagnostics.In summary, and from an operational weather forecasting perspective, this case study illustrates the combined value of synoptic analysis, ensemble prediction systems, and convective nowcasting tools for early detection and short-term forecasting of tornadic events in Portugal. It also emphasizes the critical importance of integrating deterministic forecasts with probabilistic guidance and observational confirmation, particularly in the context of high-impact but low-frequency events such as tornadoes.