A network of drifting buoys equipped with barometers can help improve weather forecasts of extreme Mediterranean storms by providing crucial atmospheric observations from areas of the sea where measurements are scarce. A new study published in the Quarterly Journal of the Royal Meteorological Society provides the first assessment of the impact of these observations during storm Harry, which affected the Mediterranean region in January 2026.
The findings come from the Mediterranean Extreme Events Experiment ( M3E ), an international initiative co-coordinated by OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale) and CMCC. By combining targeted in-situ observations with numerical modelling, M3E supports the deployment of drifting buoys in the Mediterranean basin to improve forecasts of extreme weather events and advance understanding of ocean–atmosphere interactions during storms.
Storm Harry brought intense rainfall and rough seas to several Mediterranean countries between 18 and 21 January 2026. Over three days, rainfall exceeded 300 millimetres in 23 monitoring locations and 400 millimetres in eight of them. The highest total, 482.5 millimetres, was recorded in eastern Sicily.
The storm also had devastating consequences, with hundreds of migrants estimated to have died while attempting to cross the Mediterranean by sea. On land, the storm triggered heavy landslides, including the major landslide in Niscemi, Sicily, destroying homes and forcing around 1,500 people to evacuate.
Forecasts from the ECMWF successfully predicted the heavy rainfall in southern Italy approximately seven days ahead of the event. However, forecasting precipitation in North Africa proved more challenging, partly because of small, rapidly evolving low-pressure systems that are difficult to capture accurately.
"These systems highlight the importance of collecting observations directly at sea," says Emanuela Clementi , senior scientist at CMCC and co-author of the study. "The Ionian Sea and central Mediterranean have historically had limited coverage of in-situ atmospheric measurements, despite being areas where intense storms and persistent cyclones can develop."
M3E addresses this gap through drifting buoys that measure atmospheric pressure and sea surface temperature. The observations are transmitted in near real time and made available to forecasting systems, where they can be incorporated into numerical weather prediction models.
The study shows that atmospheric pressure observations from the M3E buoys had a beneficial impact on forecasts during storm Harry. In particular, data from a buoy in the Ionian Sea contributed to improving the representation of atmospheric circulation as storm Harry crossed the region.
An additional experiment compared forecasts using the available Mediterranean drifting-buoy observations with forecasts in which these observations were withheld. The results showed significant differences in forecast sea-level pressure near the Balearic Islands, close to small low-pressure systems associated with the storm.
"The Mediterranean is a relatively small sea, but it can generate very powerful storms, and the countries around it pay a high price. With M3E we are filling a gap in the observations precisely where these storms form. Storm Harry gave us the first evidence that these data help forecasts. For CMCC it is a natural step, because a better atmospheric forecast also means a better forecast of the sea," says Clementi.
CMCC contributes to M3E through its coordination role and expertise in ocean forecasting, cyclone dynamics, extreme precipitation and observational systems. The atmospheric forecasts produced by ECMWF provide essential forcing conditions for the CMCC Mediterranean Forecasting System ( MedFS ), which operates within the Copernicus Marine Service.
Since observations are essential for better understanding and forecasting these processes, CMCC also contributes directly to expanding the observational network by providing and deploying additional drifting buoys, including in the Tyrrhenian Sea, to improve spatial coverage across the Mediterranean Sea.
The buoy observations also offer an opportunity to better understand how the ocean and atmosphere interact during extreme storms. By bringing together in-situ observations, weather forecasting and ocean modelling, M3E promotes an integrated approach supported by a partnership of European and US institutions and endorsed by the World Weather Research Programme (WWRP).
The research identifies small-scale low-pressure systems as a priority for future observational campaigns, as better coverage of these features could help reduce forecast uncertainty and improve understanding of the local impacts of Mediterranean storms.
Building on these initial results, plans are underway to expand the observing network from autumn 2026, with seven drifting buoys acquired by CMCC set to be deployed in the Tyrrhenian Sea, alongside additional deployments in the Ionian Sea. These new observations will strengthen coverage in areas where improved data are particularly important for forecasting extreme events.
Read the paper:
Lavers, D. A., et al. (2026). The Mediterranean Extreme Events Experiment and storm Harry in January 2026. Quarterly Journal of the Royal Meteorological Society. https://doi.org/10.1002/qj.70325
