Snappledagain's Blog

Vent now. Fix later.

Bolts From the Blue

You don’t always hear the rumble of lightning that flashes on the other side of the ridge. And of course the flash is out of sight too. Nevertheless lightning is nearby. The “Bolt out of the blue” phenomenon is a real thing. A distant thunderstorm can easily hurl positive cloud-ground (+CG) strokes of lightning up to fifty nautical miles (about 92 kilometres). The charge at the point of contact with the ground is how the description of polarity is derived, and at that point on the countryside there could be completely blue skies overhead. Further, that type of lightning has great destructive potential.

With no way to see or hear the phenomenon even when it could still affect you, one must refer to instrumentation. Pilots groping their way through clouds without any outside visibility have understood for decades that another reference must be used to ensure the safety of their flight. The instruments that are aboard all modern aircraft illustrate radar returns of water droplets (representing storm clouds) and lightning strikes (representing thunderstorms) sensed by onboard devices and presented as data on their instrument panels. Now a similar capability is available on the monitor of your desktop, or even a tablet, and very soon, even the screen of your mobile phone.

Lifeskill Rescue Services of Banff, Alberta, Canada has installed and calibrated a network of sensitive receiving antennae’s capable of detecting lightning at ranges of upwards of two thousand kilometres. The network can differentiate between what hits the ground, and what occurs aloft within a cloud, or between clouds. An important distinction as nearly ninety percent of all the lightning that occurs in south-western Canada stays overhead, and is no worry to us terrestrials at all (the inverse is true when you get north of sixty. E.g. in Norway some ninety percent of the lightning seen is CG, as at that latitude the atmosphere is more compressed toward the ground, and that makes grounding strikes more likely to occur).

If you are engaged in activities that take place outdoors then you are potentially vulnerable to the effects of lightning. Everything from the local rodeo to sailing regattas. Hikers and mountain climbers, and of course any business that carries on activities in the outdoors. Golf courses. Chairlift and passenger gondola operations at mountain resorts. If you are outside, and there is lightning in the vicinity, then it is simple gamblers chances as to whether or not you could be affected.

It is important to point out that no-one can (yet) predict where and when lightning will actually occur (At least, over areas that are much larger than a football field. And even then, for only a few seconds before the discharge occurs). That being said, much can be inferred from where it has been seen over the last couple of hours, and has just been observed in the last few minutes. Patterns clearly emerge when lightning is viewed in real-time.



The static image shown above is grabbed at the end of a two hour run of lightning activity from two different storm cells, beginning in the west around Vernon and Kamloops, and steadily, and predictably, marching to the north-east. The southern storm steam-rolled right over the south end of the town of Revelstoke. Observing this in real-time one would have to be wilfully ignorant to fail to understand where the lightning was most likely to occur next. Note that in this image only +CG is illustrated … and those strokes only represent about 4 percent of all the lightning being observed at the time. But once again, we really only need to concern ourselves with what hits the ground. Lightning aloft is of concern to pilots, not the rest of us.

Pilots do need to be careful to avoid flying toward such a formation. On the ground we need only be aware that it is coming to us, and hopefully with sufficient advance notice that allows one to take basic precautions. That service, alerting, is the second part of the Lifeskill system.
In the screen grab just below, another coherent storm was clearly visible moving toward Banff from the north-west.



The red dots are all of the Cloud-Cloud (CC) and Inter-Cloud (IC) (positive and negative). The black diamonds are derived from calculations done to estimate the centre of the thunderstorm cell. The +CG strike (Yellow bolt) that was thrown out ahead of the advancing storm to ground against the NW corner of Rundle Mountain could hardly have been a surprise to anyone monitoring the activity at the time. Once again, this storm showed predicable movement for a couple of hours prior to running into the area of the Banff town site, and the Lifeskill Alerting service had indeed issued a Lightning Alert for potentially impacted facilities that afternoon. Not just in the five minutes when the storm cloud was visible on the north side of town, but a full half-hour prior to the storms arrival. Those red-coloured “range rings” represent facilities being guarded, and the radius of each is 5000 metres. Notice too how Lifeskill could also have predicted how the main body of a storm could pass to the east or west of the facility. In such a case, an alert would still have been issued (as lightning is nearby). But on this day, the alert was upgraded to a warning the moment strikes were observed to have crossed the red line, as it was apparent the facility at the centre of this ring (Its position denoted by the green dot) was about to get steam-rolled by thunder-storm activity.

Blue-skies overhead? Open the browser on your computer and have a look “over-the-horizon” to see if there is anything to track as your business operations get going for the day. Dark overcast with some rain falling? Do the same thing. Open a browser and see if something is happening nearby that you could not possibly detect with your eyes and ears alone. At least, not until the problem is almost directly overhead.

The bolt out-of-the-blue phenomenon? Obviously you are not going to close for the entire day when there is only the remotest possibility of being hit by lightning with blue skies overhead. But if it happens, you now have the tools at hand to understand what just occurred, where the stroke emanated from, and defend yourself from lawsuits. It is reasonable to operate with blue skies overhead, and being able to demonstrate that you took tangible steps to defend your facilities (Lifeskill Lightning Detection and Alerting Services), that it was clear at the time you were open, and that a stroke emanated (unpredictably) from far, far away, is a solid defence to the decision to continue operations.

The economics of this service are a crucial consideration as well. Balance the cost of the service against what it costs to be closed for an entire summer afternoon. In many operations the subscription will pay for itself in one day. Vastly improved situational awareness about lightning in the vicinity will allow you to make informed and objective decisions about operations. No more guesswork. No more stressing about when lightning might be about to occur, or being surprised when it does occur. Or, being closed for no objective reason whatsoever.

The old way of assessing lightning risk, the “Gamblers Chances”, i.e. “30% chance of lightning in the region” is, and always has been, an absurd way of determining risk. You do not need to know the chances, you need to know when it is actually going to affect you. From a business perspective, who cares what is happening ten miles down the road. Unless, it is headed your way.

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Written by snappledagain

07/11/2016 at 11:03

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