Unusual sea level fluctuations startled residents and visitors along the Valencian coast on Thursday morning. The Agencia Estatal de Meteorología (Aemet) confirmed a rare meteotsunami. Also known as a “rissaga,” the phenomenon caused the sea to retreat abruptly, then surge back at beaches in Xàbia and other coastal areas, disrupting the shoreline’s usual calm.
Aemet said atmospheric gravity waves triggered the event, causing rapid changes in surface air pressure. In Xàbia, pressure oscillations reached up to four hectopascals, with the sharpest instability recorded between 10:10 and 10:20. These abrupt shifts changed the weight of the atmosphere pressing down on the sea, creating what meteorologists call an “inverted barometer effect.” The water level moved in the opposite direction to the pressure change. The Puertos del Estado tide gauge network tracked the shift.
In the port of Gandía, water levels dropped by 70 centimeters in just five minutes, falling from a peak of +0.336 meters at 09:06 to -0.371 meters at 09:12. Aemet explained that a meteotsunami occurs when an atmospheric wave resonates with the sea, transferring energy and driving dramatic water movements in harbors and on beaches. The mechanism closely resembles the “rissagas” that periodically affect the port of Ciutadella in Menorca.
Such events are not unprecedented along the Valencian coastline. On 23 July 2017, several towns experienced sudden sea surges officially classified as a “rare maritime phenomenon” in the Sinobas notification system. Torrevieja and Elche were among them, as were Santa Pola and El Campello. The latest episode highlights the region’s vulnerability to atmospheric disturbances, even outside storm season. Similar weather-driven disruptions have affected other parts of Spain, including when a recent storm system brought heavy rainfall and temperature drops across the country.
Meteotsunamis differ from seismic tsunamis: rapid atmospheric pressure changes cause them, not underwater earthquakes. Though typically less destructive, they can still threaten coastal infrastructure and beachgoers. They are most likely in enclosed or semi-enclosed bays, where resonance can amplify the effect. Spanish authorities continue to monitor these events with tide gauges and atmospheric sensors, issuing early warnings when possible. Understanding what triggers meteotsunamis and how they develop is increasingly impressive for coastal management, especially as climate variability may influence their frequency and intensity in the Mediterranean.
