Observations and Numerical Modelling of Strong Meteotsunami of 13 June 2013 on the East Coast of the USA

Abstract:

A strong "derecho" (rapidly moving lines of convectively induced intense thunderstorms) was

generated over the Midwestern United States on 12-13 June 2013 and propagated across the

Appalachian Mountains to the Atlantic Ocean. Three hours after the derecho crossed the Atlantic

coast, a ~2-m high meteotsunami wave was reported to have hit the New Jersey coast. Significant

tsunami-like oscillations, with wave heights of ~0.6 m, were also recorded by a number of tide-
gauges located along the eastern seaboard from Nova Scotia to South Carolina, at Bermuda, and

by open-ocean DART 44402. These observations triggered the tsunami-alert mode of the DART

station. Intense air pressure disturbances (with pressure change of 3-6 hPa in 20 min) and strong

winds were observed at a number of National Oceanic and Atmospheric Administration (NOAA) and

Automated Surface Observing System (ASOS) stations to be propagating simultaneously with the

derecho system, indicating that the pressure disturbances were the primary cause for the sea level

oscillations in Chesapeake and Delaware bays. The air pressure disturbance continued to propagate

seaward over the continental shelf, thereby generating long waves via Proudman resonance at

those areas of the shelf where the propagation speed of the air pressure disturbance matched the

long wave speed. Upon reaching the shelf break, the long-waves were partly transmitted (reaching

Bermuda 5 hours later) and partly reflected (returning to the east coast of the US and Canada 3 to 6

hours later). A numerical barotropic ocean model forced with idealized air pressure and wind fields

was used successfully to simulate the event. The meteotsunami arrival times and maximum wave

heights obtained from the model closely match the measured values and confirm initial assumptions

regarding the partitioning between transmitted and reflected meteotsunami waves.