Okay there's something really cool I've just learned. If you are continuously recording air pressure e.g. as part of your home automation setup or a weather station then you should really check the data of the last 24h.
You should be able to spot the pressure wave from the volcanic explosion in Tonga earlier today.

It reached my setup in Kaiserslautern at about 20:30.

Interesting. According to the explosion happend around 5:27 (my localtime) at 20.5 175.4. According to google maps thats 12142km away from me.
12142km /15h = 809.5km/h = 225m/s so Mach 0.66 at sea level. Shouldn't it be a bit closer to the speed of sound?

On the other hand, it probably was initially. But the length of the wave front grows the father it gets away, from the source. It should get slower as it has to move more and more air, but it doesn't get any additional energy.

Okay my coordinates where wrong. Thanks to @x44203 for pointing that out. I've fixed them and I did some calculations for all of the other reports in this thread.

Given that most of it was guestimated from screenshots, it's amazingly close.

I also made little jupyter notebook to play with the data. I'll clean it up and upload it later.

I also tried calculating the speed at each location using the relative distances between them and then propagate that back to 4:27UTC find the point of origin....

It did work kind of ... you squint at the right location.
Green is T-5min, red is T-0 and blue is T+5min.

However if you look at the full map, it's a mess.

Not enough data points, the locations are not spread out wide enough, the timing is off, and there is some weird map projection stuff going on....

I've added some explanations and parked my notebook here:

So if anyone wants to do a proper analysis feel free to use it a starting point.

Since everyone is liking and boosting this like crazy and I don't have a soundcloud and we don't do that over here....
I did not come up with the idea, I just came across it over on the birdsite. So credit where credit is due:

@sebastian It arrived in Aachen about 5 Minutes earlier. Sensor is a (China clone) BMP180 in my office.

@sebastian Here too, but my data hasn't the same resolution as yours.

@sebastian oh and if one wants to see how special this event is, look at the last seven days. The line is very smooth until the pressure wave.

@leah Same here. Really impressive. I didn't expect it to be that easy to spot.

@sebastian I arrived at closer to 16.000 kilometers O o

@morre Maybe I messed that up then. Or Google maps decided to do weird stuff. Let me check tomorrow.

@morre @sebastian Did some checking, the coordinates I used from the tsunami warning seem quite a bit away from Tonga. Using Tonga as a starting point I get about 0.9 Mach which would be closer to my intuitive expectations.

@sebastian @morre You did a mistake with the coordinates. You probably used 20.5 / 175.4 as lat/lon while in reality its -20.5 / -175.4

@sebastian spherical-surface radial attenuation. nonlinear in strange ways

@hyratel Probably. Also my coordinates where off by about 4000km. Oops.

Heres the fixed version:

@sebastian Maybe it is traveling slightly above 90km height? That gives a speed of sound of slightly above 200 m/s, and at that height there is a positive gradient, which bends the sound waves towards earth.

@sebastian Hmm, I'm getting 16789 km which should be about 14 hours

Interesting to see it average out to Mach 0.9. I suppose that might be because it's not travelling entirely straight (bouncing between the ground and some atmoshperic layer, or because most of it is propagating a bit higher in the atmosphere. The speed of soumd reduces with altitude because it's colder there. The measured propagation speed is the speed of sound at about 8.5km altitude (standard atmosphere)

@tsia_ Make sense. The shortest way to Tonga is nortwards. At least according to google maps.

@sebastian Wow. Unfortunately I just turned my setup off a while ago. Would have been cool for my air pressure organ:

@sebastian I had a moment of "wait, that's too late", because it was way earlier here in Berlin.

But 500 kilometers really make a difference for pressure waves.

@sebastian Detected in Edinburgh with peak around 1845 UTC.


… und an sich gibts bei eve weather nur alle 10 Minuten den datenpunkt

@kumicota BME280 I got as part of a weather station kit a while ago.

@sebastian oh wow, that is so cool, thanks for pointing it out!
I have data from Frankfurt (the peak is around 20:25)

@sebastian @hierarchon it was even audible here in Aotearoa, nearly 3000km away!

if located in europe, 6 hours later you should see the long path with approx. half of the pressure

@spel Right I almost forgot about that.... There it is. Around 2:21 right on time.

@athairbirb @sebastian Sorry - I have been posting on twitter but forgot to replicate here. Here's my barograph from the 24 hours. The first wave is visible around 19h30 and then the second wave coming around from the other side of the planet, at around 03h00.
Astonishing that this was recorded here, 16000km and 19 hours from the event, a wave that travelled at over 1000km/h

@athairbirb @sebastian I also extracted the data from the weewx sqlite database and graphed it with Libreoffice, for clearer details.

@sebastian That is really cool to seen I thought it would not be possible to see. I wonder how strong it was directly in Tonga

Cool, the pressure wave reached us as well. Thanks for the hint.

@sebastian My phone has an atmospheric pressure sensor, which is recorded by an F-Droid app called AtmosphereLogger.

It's sensitive enough to detect altitude changes of a few meters when walking to the nearby supermarket.

Picked up the pressure wave from the Tonga volcanic explosion last night here in Sicily.

@sebastian wow, we have the same atmosphere, and... *boggling*

@sebastian Some low-resolution data (only all 60 seconds), but I think the "burst" and "drop" are from Tonga. Sensor in Schleswig-Holstein.

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