Sunday, January 16, 2022

Massive South Pacific volcanic eruption sends shockwaves around the globe that were measured in Memphis

Many of you may have seen the news that an undersea volcano very near the island kingdom of Tonga in the South Pacific erupted with violent force early on Friday morning (January 15) Memphis time. The force of the explosion sent ash some 100,000 feet into the air and generated a shockwave that traveled around the world, in both directions (eastbound and westbound), from the epicenter. Satellite views of the colossal eruption are mesmerizing:

In the top two loops, you can see the "waves" emanating outward from the blast. That is the "shockwaves" that circumnavigated the globe. 

Later in the day I started seeing some tweets about changes in barometric pressure in the United States that could be traced directly to those waves propagating around the world through the upper atmosphere. 

Using timestamps from a few of those other pieces of information, I then turned to the data from my Davis Vantage Pro2 weather station, which archives all weather elements every five minutes around-the-clock. Below is that data plotted on a line graph. You can see that graph below.

The timing of the first (eastbound) wave that traveled across the Pacific Ocean and then the United States would have likely been unnoticed had I not known what time to look. But there it is, between 7:40-8:00am Friday (first red box below), represented by a slight rise in pressure, then a return to the slow fall that was in progress ahead of the winter storm that arrived Friday night.

The second wave, coming from the east, and which had traveled almost three-fourths of the way around the globe, was much more pronounced about 16 hours later. Notice the second red box below. The pressure was naturally falling towards a low around 5am as surface low pressure was passing by to our south during the winter storm. However, there was a large rise in pressure that started just after midnight and lasted about 20 minutes, followed by a major drop of nearly 0.10" of mercury in 10 minutes between 12:20-12:30am. Pressure values then returned to "normal" about 30 minutes later. So the wave that passed overhead unnoticed to all of us I am sure, lasted about an hour and included a sudden rise and then precipitous drop in pressure.

A trace of the raw barometric pressure from MWN's weather station in Bartlett recorded two pressure changes that were the result of the shockwaves emitted by the explosion of Volcano Hunga-Tonga, some 6800 miles away. The first, around 8am Friday, was relatively minor. The second, some 16 hours later or just after midnight Saturday morning, was much more noticeable to the instrumentation, if not the general public. 

Of course our prayers are with the 100,000 inhabitants of the island of Tonga in the south Pacific northeast of New Zealand, who are cut off from the world and likely dealing with significant issues from one of the largest volcanic eruptions in the modern satellite era, which allowed the rest of the world to see it in stunning detail.

Erik Proseus
MWN Meteorologist

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