The word derecho is defined as a “long-lived windstorm associated with a band of showers or thunderstorms” and it was heard for the first time by many of us during June of 2012. Well, here is another weather-related word that most have likely not heard before – meteotsunami. Meteotsunami is a rare type of tsunami that is caused by a weather event rather than from seismic activity, and it appears that one may have hit the New Jersey coast on June 13 shortly after a line of strong thunderstorms moved through the area. Those strong thunderstorms actually propagated from the Midwest to the east coast over a twelve hour period as part of a weather system that the National Weather Service subsequently labelled as a “low end” derecho, not quite as intense as the June 2012 derecho. Strong weather systems like these two derechos can cause jumps in air pressure spawning waves that act like tsunamis and it is possible that air pressure fluctuations from this month’s derecho may have caused a 6-foot wave to hit the New Jersey coast with Barnegat Light (Ocean County) bearing the brunt of the wave.
According to an eyewitness account from someone who was spear fishing near the mouth of Barnegat inlet just south of a submerged northern breakwater, the sequence of events was as follows:
Around 3:30pm on Thursday June 13, 2013, the eyewitness was spear fishing near the mouth of Barnegat Inlet; just south of the submerged northern breakwater. Earlier in the day around noon, thunderstorms had moved through the area. By 3:30pm the weather was overcast with a light east wind. At approximately 3:30, the outgoing tide was amplified by strong currents which carried divers over the submerged breakwater (normally 3-4 feet deep). This strong outrush continued for 1-2 minutes and eventually the rocks in the submerged breakwater were exposed. The eyewitness backed his boat out before being sucked over as well.
At this point, he noticed a large wave coming in, approximately 6 feet peak-to-trough and spanning across the inlet. The upper 2 feet of the wave was breaking. This wave occurred in conjunction with a reversal of the current such that even though the tide was going out, a strong surge was entering the inlet. This surge carried the divers back over the submerged reef and into the inlet from where they were picked up. On the south jetty three people were swept off the rocks which were 5 to 6 feet above sea level at the time. At least two were injured requiring medical treatment. There was no more strong activity after about 5 minutes.
Thirty tide gauges along the east coast confirmed a rise in water on that day, up to nearly a foot in spots, suggesting something indeed was going on. It could take researchers months to confirm this one way or another and other possibilities are being considered including a possible geologic disturbance such as an underwater earthquake or landslide off the continental shelf. The “slumping” at the continental shelf east of New Jersey may have played a key role.