http://www.vaisala.com/Vaisala%20Docume ... Gookin.pdf" onclick="window.open(this.href);return false;
The article has considerable useful information. However for such a serious attempt at outdoor
lightning protection I was surprised at how little actual new information was about being outdoors in actual landscapes. Most of what they noted is somewhat old news. I could write several pages here but the below will suffice. At the top of the article is the statement:
"Most ground strikes occur below the cumulonimbus cloud, but many still strike beyond the shaft of rain or beyond the edge of thecloud. This is important for lighting safety since it doesn’t need to be raining or even cloudy overhead for you to be in danger from
lightning."
And then that is the last such is mentioned. Even though they have a significant section on how step leaders work, they don't bother connecting the reality that step leaders tend to be much closer to the ground wherever rain is falling especially heavy rain because electrolytes in water make it far more conductive than even humid air. Most outdoor people, especially Easterners understand through experience that the nastiest closest
lightning tends to occur during initial onset of heavy rains when a front arrives. Also with thunderstorms of course, where rains fall, towering cumulus clouds above contain most of the positive charge that is seeking the negative electrons down on the ground. Thus when outdoors after one hears thunder in the distance then somewhat later feels the first drops of water, one ought immediately get alot more serious about seeking the best local area for protection because those step leaders are likely to then be much closer to the ground.
The article also did not have much new to say about best places to stay in terrain other than avoiding tall objects. For instance trees are not always a poor choice...if they are within a dense forest and one is not beneath or near one of the taller trees. In fact the dried leaf matter below many conifers is an excellent insulator across which
lightning is not likely to flow. Any
lightning hitting tallest trees in a forest on deeper soils is more likely to follow the main trunk down into the ground and then expand out beneath the ground. Of course such places below tree canopies are also certain to be more pleasantly drier during rains. Find spots that while under leaf canopies are not directly adjacent to any larger trunks.
In granite geology, bedrock tends to be broken up into regular joint cracking. Some are wide enough to fit a truck while many others are rock touching rock. Inside those narrower cracks is all matter of plant roots, soil, and moisture.
Lightning ground currents are more likely to follow such joint cracks versus other areas of bedrock because the resistance is likely less. So don't make your stand over a narrow joint crack. In granite geology there are often flat coarse granite sand areas aka gruss flats, between bedrock that are well drained and relatively dry versus other soils. Good places to pitch a tent on.
Lightning ground currents tend to flash spreading over the surface of wet bedrock are likely to go around such sand.
In uneven mountainous landscapes, the safest areas tend to be at the base of steep slopes (not small slopes). But perferably in dry areas thus not where seeps come out. Those areas also are more likely to have talus that often has ready places to get beneath and place gear out of rain. So storms are brewing and you have some time to move about in the local landscape? Head to the base of talus slopes.
An area to avoid is landscape knees. Say there is flat terrain that drops off at a knee down to lower areas. Stay well away from such knees even though they may not stick up like a tree, if a step leader up in the air is moving across from the lower areas towards the knee, as soon as it meets the knee it may draw streamers up and complete the path causing bolts.
Another strategy to be significantly more safe is to carry a super light plastic trash bag like this that one:
http://www.thenerds.net/GENUINE_JOE.Gen" onclick="window.open(this.href);return false; ... 04046.html
that one can totally get inside while stooping in the
lightning position per the article. However the bag needs to be like new WITHOUT ANY PIN HOLES. This will make your otherwise very conductive body seem to be a far higher electrical path versus anything adjacent so any
lightning air or ground currents are likely to go around you. One bag is less than an ounce and takes up little space.
David
http://www.davidsenesac.com" onclick="window.open(this.href);return false;
