A Triple Jeopardy Flood Event: Coincident Arrival of the 2022 Tonga Tsunami with a Storm Surge and Meteotsunami on the East Coast of the United States

Abstract On 26–27 December 2004, a major tsunami, generated by a megathrust earthquake off Sumatra Island, reached the Atlantic Coast of the United States. The arrival of the tsunami coincided with a storm-generated meteotsunami, resulting in a double jeopardy oceanic event. Similar conditions occurred on 15 January 2022, following the eruption of the Tonga-Hunga underwater volcano in the tropical Pacific. The eruption generated atmospheric pressure waves that propagated around the globe several times at roughly the speed of sound. These waves forced pronounced tsunami waves that subsequently impacted the Atlantic Coast of the United States. Almost simultaneously, a deep extratropical cyclone crossed the region on 16–17 January. The cyclone, which had formed over the northern Gulf of Mexico, propagated northeastward as a “bomb cyclone” having a rapid pressure change of 36 hPa (24 h) −1 . Strong high-frequency (period < 3 h) atmospheric disturbances accompanied the cyclone. Both the large-scale low and the markedly enhanced atmospheric disturbance reached full strength in the proximity of Atlantic City during the early morning of 17 January. This combination of three hazardous events resulted in a triple jeopardy threat to water levels along the eastern seaboard of the United States, consisting of a cyclone-generated storm surge, a meteotsunami caused by high-frequency atmospheric disturbances, and a tsunami forced by the Tonga air pressure waves. Severe flooding occurred in the Atlantic City region, where sea levels rose by as much as 150 cm above background. Here, we examine the individual properties of the three atmospherically generated processes that gave rise to the cumulatively high sea level response. Significance Statement This study examines the coincident arrival of the January 2022 Tonga tsunami, a local meteotsunami, and a storm surge on the Atlantic Coast of the United States. The 2022 Tonga-Hunga volcanic eruption produced tsunami waves that were recorded along the entire East Coast of the United States, over 13 000 km from the source region. A unique aspect of these oceanic waves was their generation by atmospheric waves that several times circumvented the globe. The atmospherically induced Tonga tsunami, combined with the storm surge and local meteotsunami, resulted in a “triple jeopardy” hazard to the U.S. Atlantic Coast. Such events clearly need to be taken into account in any marine hazard warning and mitigation planning.