I've never ever seen a storm alert from my Suunto watch until today when we are in a heatwave and there is not a single cloud on the sky
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My V2 works as expected. It goes off when a storm is approaching.
I sit at work opposite someone with a Garmin and they generally go off pretty close to each other.
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It would be interesting to know how the programmers have decided what triggers a “storm alert”. I’m fairly impressed with mine and that it doesn’t trigger a storm alert every time I go up an elevator, or shortly after takeoff in an airplane (both of which involve rapid pressure decreases—perhaps too rapid?). To issue a proper “storm alert” of course would require more information than the sole input of a certain pressure change and a look at some actual weather inputs, but I consider it a useful (if limited) tool in the chest, and if nothing else, at least a “nudge” to take a 360 degree look around and assess what I see…but not a reason in itself to open the umbrella and seek shelter
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The watch waited years for its big moment and everyone immediately questioned it. Poor thing
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@skifast12 The atmospheric pressure decreases with height (the weight of the overlying air column lessens as you ascend). It also depends on the meteorological situation. To isolate the meteorological situation pressure by removing the effect of the height on the pressure, meteorologists “correct” the actual pressure to a kind of normalized pressure at sea level (using height, temperature, humidity, …). This allows to compare two pressures measured at different point with different height. It is on this sea-level corrected pressure that the drop is supposed to be computed.
So, if you use an elevator/take an air plane, the real pressure lowers but the corrected sea-level pressure remains mostly the same.
The atmospheric pressure shared by meteorologists in communication medias is the sea-level pressure. -
That’s all very theoretical and not how it works in a watch.
On a plane, the air pressure in the cabin is kept at a constant 0.6 - 0.8 atmosphere (depending on the plane type) and for good reason.
An elevator will not go high enough to cause a big enough drop in air pressure to trigger an storm alert.
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Never a single accurate alert in my case (S9PP). I do not trust it at all.
J
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I live in the Alps, where the weather in the mountains can change drastically very quickly. So the “Storm alert” is a welcome feature. Of course, this does not mean that there will be a storm or severe weather, but that you should be more attentive and observe your surroundings even more.
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@LGoSo I’m an airline pilot so I understand how atmospheric pressure works. It’s just a watch though without any access to met information, not even to actual altitude data (aside from GPS which isn’t very accurate in the third/vertical dimension)…it’s just a dumb pressure sensor. The storm alert is generated by some software code that someone has decided what triggers and what doesn’t. I’m guessing that the storm alert doesn’t trigger with the rapid ascents I mentioned because it has been programmed to look for longer-term pressure drops; perhaps over the span of an hour or two, which might actually miss fast-moving frontal systems.
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@elbee Been to a big city with high rise buildings lately? A frontal system might only drop 0.05 inHg, with stronger storms around 0.30inHg, which convert to 50 and 300 feet of elevation change respectively. The Burj Khalifa as an extreme example is 2,717’ tall. Airplane cabin altitudes vary immensely but normal cruising altitudes are around 7,000 to 8,000 above sea level, so there has to be something preventing the storm alert from triggering from these everyday events. We’re all just guessing unless Suunto programmers let us in on their logic…
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@skifast12 according to suunto manual it is triggered only by the differential change of atmospheric pressure
“The Alarm: If $4 hPa is lost in 3 hours, the watch beeps, vibrates, and shows a storm symbol.”
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Planes fly even higher than 7000 or 8000 (meters is the most obvious units) they fly at 10000 til 12000 meters. That’s way higher than Everest. On Everest normal people need oxygen masks. Planes do have equipment to keep the pressure in the cabin constant. At about 0.6 atmosphere and 0.8 in more modern planes. Don’t take that from me, don’t assume, but look it up.
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@thanasis 4hPa is around 50m of height difference. So I think that it is the sea-level pressure which is used. If not, the alert would be triggered all the time. The watches have another source of information with the GPS that allows an estimation of the height independent of the estimation of the height from the pressure. Probably they are using the GPS height estimation to estimate the sea-level pressure.
In Coros watches, both pressure are available: sea-level pressure and station pressure. I don’t know for Suunto as mine doesn’t have a barometer. -
@thanasis 4hPa is around 50m of height difference. So I think that it is the sea-level pressure which is used. If not, the alert would be triggered all the time. The watches have another source of information with the GPS that allows an estimation of the height independent of the estimation of the height from the pressure. Probably they are using the GPS height estimation to estimate the sea-level pressure.
In Coros watches, both pressure are available: sea-level pressure and station pressure. I don’t know for Suunto as mine doesn’t have a barometer.I am only stating what suunto states. not what it could be
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@LGoSo that is just not true. GPS is never used while not in activity. Also Coros documentation clearly states:
How to trigger the Storm Alert?
A drop of 4 hPa or more in 3 hours.
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@aiv4r Coros states clearly also that you have to use the sea-level pressure for weather change (https://support.coros.com/hc/en-us/articles/360040255171-Widgets-Barometer) :
“Station pressure is measured at a station without any altitude adjustment like from a house or the top of a mountain. It will change at various altitudes.
Sea-level pressure is the station pressure adjusted to the sea level. It is often used for predicting weather changes at the current altitudes.”
But I haven’t found information on how the pressure can be adjusted if the GPS is not used.
So I don’t know how the watch works, just guessing, but I am pretty sure about the physics behind. 4hPa is about 50m of elevation. 4hPa in 3 hours means that climbing a mild mountain would trigger the alert all the time and it is not the case. So, a correction of altitude should happen. Before GPS watches, the difference between height elevation and change of weather was done using the fact that the weather is changing the pressure slowly and climbing was decreasing the pressure very fast (not very efficient IIRC). Probably this is also used.
But if you stay at the same elevation, than pressure and sea-level pressure can be used indistinctly to trigger a weather change.
I think that the information given by Coros and Suunto is insufficient to understand what they are really doing. -
@LGoSo I think we agree on some things, but we are talking about different things
One thing it is how altitude and barometer and GPS interacts during the activity. Other thing is “Storm alert” and completely third thing is Weather widget. Storm alert only uses barometer as far as we know from various discussions and documentation. But of course we do not know what we do not know. -
@aiv4r I think that they should be connected: impossible to have an alert without taking into account the pressure difference because of the height. Anyway I have set my storm alert to ON (was OFF) to see how it works when not in activity. And it should nearly trigger every day I go to work if altitude is not taken into account (working at 100m, living at 54m which is ~5.5 hPa of difference).
Yesterday I was at work and these are the measurements of my Coros (40 minutes apart, first @work, second @home:)
Station pressure: 997.8 -> 1003.4 hPa
Sea-level pressure: 1009.1 -> 1009.9 hPa
So a height correction is applied despite the fact the watch was not in activity mode.
But how is an open question.
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