This was an interesting tidbit to read. I usually don’t post articles, but this one is worth it, and I can’t see that I’ll be able to find it in the future on Accuweather. Here’s the link, in any case, to the column, this one or another one by Joe Sobel.
Joe Sobel’s Column
POSTED: 11:50 a.m. June 27, 2003
The thoughts expressed in this column represent Joe Sobel’s personal speculation. While they are considered in formulating AccuWeather forecasts, the opinions of many other AccuWeather meteorologists are also considered.
This discussion is updated only the days that Joe is available, usually Monday-Friday. Check the date above and come back often!
So, do you think all lightning strikes are created equal? The answer to that question is a resounding no. Not only are no two lightning strikes the same, the may actually be of different polarity, that is carrying a negative or positive charge.
Most lightning strikes are negative, that is negatively charged ions flow downward from the cloud to the ground in what is call the stepped leader, and then a return positive charge flows from the ground to the cloud which is the brilliant flash that we see. In a positive strike the stepped leader is a positive flow of current and the return stroke from the ground is negative.
A few interesting differences between the two, according to an article in the June 2003 issue of the American Meteorological Society….
1. Positive strikes account for only about 10 percent of cloud to ground lightning stokes.
2. The highest current flows are thought to be associated with positive lightning.
3. Cold season thunderstorms are more likely to produce positive lightning strikes.
4. Weakening or dissipating thunderstorms tend to produce more positive lightning strikes.
5. Positive flashes are usually composed of a single stroke, whereas about 80 percent of negative flashes contain two or more strokes.
6. Positive lightning strokes often involve long horizontal channels. It is presently not clear why.
7. There also are bipolar lightning strikes in which current flows reverse during the event.
I don’t know about you, but I found all of this rather “shocking”, but whatever the weather I hope you will be “positive.”