Lightning, what to do if you are at altitude:the guide.And beware of 'positive' lightning

What to do if a lightning storm breaks out while you are on a trip to the mountains?There are things to pay attention to and others not.And above all, there are things you absolutely shouldn't do.Here are the tips from the Alpine Guides

BOLOGNA – During the summer season, when it is more common to go on trips and climbs at high altitudes (not always having experience), one of the natural elements to which you need to pay close attention is lightning.They can in fact represent a danger that should not be underestimated and correct information and preparation on the topic is essential.Know how to behave if you find yourself unexpectedly under a thunderstorm with lightning at high altitude, like find shelter (and what kind of shelter) and also know what is really dangerous and what is not.You must not stay at high altitude, you must never, ever stay under a tree, it is possibly better to take refuge in a cave (without touching the walls) or squat like a hedgehog with feet together.However, it is not true, for example, that carabiners and key rings attract lightning.To spread a little 'guide' on how to deal with lightning in the mountains are the Alpine guides:in a note from the National Alpine Guides College, an interesting story is reported interview with Giacomo Poletti, environmental engineer and meteorology teacher for the Trentino Alpine Guide College for over 13 years.It's full of advice and useful information on how to recognize potentially dangerous weather conditions, preventive measures to take and behavioral strategies in case of sudden storms.And it is also explained how to recognize the 'positive' lightning from those 'negative'.

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Why are mountainous areas more prone to lightning than plains?

Mountain areas are more subject to lightning strikes for at least three reasons:the first is that rocks and slopes, heating up under the sun more than the surrounding air at the same altitude, end up being a trigger point of the convective motions of the air (i.e. upward buoyancy motions).Then there is the effect of forced lifting on the winds induced by the presence of the mountains, and this also plays in favor of triggering storms right above the mountains.Furthermore, once storms arise, the peaks are at the shortest distance from the cloud base and this makes them the points often most affected.

How does lightning form?

There are various types of processes that lead to lightning.Inside the cloud the air rises:therefore, the small light particles of water or ice tend to rise into the cloud, dragged upwards by the flow, and collide with the hailstones or large, heavier drops, which instead fall towards the lower part of the cumulonimbus.Every single collision separates electrical charges (the water molecule in fact has a non-symmetrical distribution of its charges and this allows its separation by contact).As the minutes pass, the cloud accumulates negative charges at the bottom, inside the large drops and hailstones, and positive ones at the top, becoming a sort of “super” stack.By induction, at that point, the positive charges migrate from the ground under the cloud, attracted by its negative base.
The air, being a good insulator, keeps the areas of opposite charge separate, but when the electric field exceeds a certain limit, an invisible flow of electrons, called a guiding discharge, breaks away from the cloud and heads towards the ground.When it is a few dozen meters from the ground, a return discharge starts upwards from it. When the circuit between the two discharges closes, lightning explodes more frequent and classic, the cloud-earth.If the circuit closes within the cloud, it is called intracloud lightning, if with other nearby clouds, it is called cloud-cloud lightning.All potentially dangerous discharges for those at high altitude.

Are there any warning signs that indicate the risk of lightning?

Yes, but they often manifest themselves very shortly in advance, so it is essential to protect yourself in time by putting adequate actions into practice.They are almost always felt a few moments before the lightning strikes crackles in the air or hums from metal equipment;in some cases the hair becomes electrified and stands up.Furthermore, from high or pointed objects such as crosses, poles or trees, jets and flashes of luminescent, often bluish, ionized air can escape (the so-called St. Elmo's fires).All these cases are extremely dangerous because they indicate that the circuit between cloud and ground could close very soon.It's necessary immediately lower your altitude and make sure that our body and/or our equipment are not the highest things in the surroundings, a golden rule to always follow during storms.

What is the difference between 'positive' and 'negative' lightning?

I would also like to highlight the difference between negative lightning, which are the "classic" lightning strikes that fall under or near the storm, and positive lightning, which strike at a great distance from the storm because they originate from the upper part of the cloud.The latter are rare, but powerful and very harmful, often causing victims because people underestimate the danger of the storm seeing it as still distant.As a basic rule, if I hear thunder within 30 seconds of the lightning strike (ergo, at a distance of no more than 10 kilometers given the speed of sound of approximately 3 s/km) I have a potential risk.

What should a person do if they find themselves outdoors in the mountains during a thunderstorm?

There are different behaviors based on the cases but we start from the rule just mentioned:us and our equipment (even fixed ones, such as tents) we must never appear to be the highest thing around, and we must also avoid being close to higher objects, be they trees, poles or other.Let's go in order, starting from the case in which you find yourself outdoors without the possibility of finding shelter.Basically I have to quickly drop in altitude remembering that the most dangerous and frequent lightning strikes come before showers (they often fall "in hot air"); abandon ridges and peaks, the center of the channels and the exposed slopes.Once the storm arrives, I don't have to run or walk, but instead stop and protect me in depressed or concave places (in depressions, potholes) crouching like a hedgehog and keeping our feet together as much as possible, an action that protects us if lightning strikes near us because it greatly limits the differences in electrical potential between the two feet.If we were instead running or walking, a lightning strike that strikes the ground could indirectly electrocute us due to the step current - given by the potential difference between the two supports.Of course I have to avoid stopping near or under trees, especially if isolated and/or high.
If we are in a group, we have to separate, individually adopting the measures just mentioned.By staying together the risk is to produce dangerous columns of hot air which are a preferential path for lightning (the well-known "chimney" effect which is often fatal for flocks) or to conduct the current to their companions. If we're in the water, I have to get out immediately;in fact, water is an excellent conductor of current and lightning tends to dissipate on its surface.

Where to find and how to choose shelter?

In a natural cavity (grotto) or artificial (former military forts, ruins) I must avoid stopping at the entrances to avoid creating an electric arc by bridging the floor and ceiling. It's not good to even lean on the walls (especially if wet) and I must also avoid air currents (the flows can constitute preferential paths for discharges).I must therefore look for a protected internal corner where to squat without touching the walls.Sitting on the backpack is also fine.Of course, if I can reach a closed place, so be it: yes to cars (they protect thanks to the "Faraday cage" effect as long as the metal bodywork is not touched) and buildings.In the latter case, once inside, I do not open taps (the pipes can be an excellent conductor of discharges), I disconnect the cables from any sockets and I also stay away from fireplaces and fireplaces that are lit or still hot (once again I avoid potential columns of hot air).On glaciers and on snowy plains, I have to try to move to the edges of the clearings.In fact, the katabatic wind on snow-covered slopes and glaciers is often traversed sub-horizontally by lightning.

Is it true that carabiners, metal objects and smartphones attract lightning?

It is not true, let's finally dispel a false myth, there is no need to abandon them. However, they can get warm (“Joule effect”) and burn us if stray currents pass through them.The correct choice is to put them inside the backpack or in any case not in contact with the skin, taking them with us.From literature, the danger of lightning ceases when I no longer hear thunder for at least half an hour.If I have a smartphone, I could independently assess whether the danger is over by observing weather radar and/or live lightning data.

If someone is struck by lightning, what should be done?

The question requires a medical answer if we are talking about first aid;However, some aspects also intersect with the meteorological nature of the phenomenon.The majority of those injured by lightning are injured not by the direct fall of the discharge on the body (a case which is not always fatal, especially if help is provided promptly) but above all because the shock falls nearby, within a few dozen metres.We can dispel some false beliefs:the body obviously does not store electrical current and the victim of electrocution must be helped immediately as per practice, by calling 112 and following the instructions provided, with possible cardiac massage and mouth-to-mouth resuscitation.To remember that electric discharges produce violent muscle contractions, therefore it is not uncommon to see those struck by lightning with fractures.Cardiac arrests, burns and other types of injuries (for example to the eardrum due to thunder) have also been recorded.

What happens when lightning strikes the ground or a structure in the mountains?

In general, lightning that falls to the ground dissipates following fractures or wetter sections of the ground.To underline the possibility of vaporizing the sap on the trees, That “they explode” literally if hit, throwing pieces of trunk and bark even from many meters away.A disruptive effect can also be had on rock tips, although it is much rarer.For buildings, the classic damage is observed on chimneys and tiles but if the systems are well designed, they discharge any lightning strike without damage.It is precisely the improvement of the building stock that is having a role in the drop in lightning mortality observed in Italy.

Do you have any statistical data on the number of accidents caused by lightning in the mountains in Italy or in the Alps?

Lightning damage and victims are tracked by the European Severe Weather Database;while the Istituto Superiore di Sanità does not provide targeted statistics. In Italy, deaths from lightning have gone from 40/50 cases per year in the 1980s to 10/15 today, thanks to greater attention to forecasts, to the alerts guaranteed by the relevant bodies and to the technological improvement of electrical systems that avoid fatal overvoltages.In the mountains and the Alps there are overall less than 10 cases per year, but the numbers increase tenfold if we consider non-fatal injuries.

Is there a season or time of year when lightning is more frequent in mountain areas?

Thunderstorms are clearly related to solar radiation and temperatures, therefore an annual maximum is recorded in July during the hottest hours, with lightning peaks from 1pm to 5pm and frequencies that remain higher in the evening than in the morning.As the warm season progresses, thunderstorms tend to move towards the center of the ranges:for example in May and June there is a greater frequency in the Prealps, already free from snow and therefore warmer.On the watershed and in Alto Adige, however, August is the stormiest month.In September statistically there is a decrease in instability due to the shortening of the days and the arrival of the first thermal inversions, which stabilize the air column.However, it should be noted that in the Italian mountains throughout the year, including winter and nights, there is the possibility of seeing thunderstorms.In recent years, for example, we have been observing an extension of thunderstorms beyond the hot season, with lightning strikes even in January or at the beginning of winter, especially when the seas are warmer than normal.

How does climate change affect the frequency and intensity of thunderstorms and lightning in the mountains?

The intensity of the storms is increasing, as is the average diameter of the hailstones observed.There are currently no clear signals regarding the frequency of storms.Climate change is primarily leading to an increase in temperatures, with a consequent increase in evaporation from the seas, which are warmer than in the past, and therefore in the humidity available in the air.High temperatures and high humidity are both fundamental fuels for the “time machine”;however, they are not sufficient, given that an "ignition" is also needed.The trigger is given by fresh currents at altitude or in any case by winds at altitude, conditions which however the African anticyclone dampens for long periods.We are therefore faced with a more extreme climate, with even long anticyclonic phases without instability, alternating with drastic worsening and more intense storms than in the past.Suffice it to say that in July last year in Friuli the European record for the diameter of a hailstone was set, 19 centimetres.The statistics on lightning are still short and the data varies a lot from year to year, so it is not possible to say whether their number is increasing or not.

Are there any significant changes in lightning risk that we can expect in the future?

As mentioned, in a warmer world it is reasonable to expect more intense and extended storms during more months of the year, in line with the trend that is already being observed in Italy.

How can I find out about the probability of thunderstorms?Can they be predicted?

Thunderstorms are predictable, although not punctual.However, I invite you to inquire with both regional bulletins or by consulting new experimental products, the result of the work of professionals, such as pretemp.altervista.org for Italy or, at a European level and in English, estofex.org.Both sites evaluate the forecast of storms for the following day in terms of probability, with maps and text, a fundamental aid.In the short term, however, the support of weather radars, which read storms and their movement, and above all of sites that report live lightning strikes, such as lightningmaps.org And blitzortung.org.