I have been showing lightning counts on TV over the past few weeks with all our thunderstorms. I show total lightning counts per 30 mins but I also show the number of negatively charged lightning strikes and the positive charged lightning strikes.
Many of you have asked what’s the difference? Well, it’s very significant and very important to how dangerous the lightning can be and sometimes how strong or severe the storm can be. So let me explain and I think you’ll see why it’s important to show these numbers.
Negative lightning refers to the polarity of the lightning strike. Just like on any battery that has a + (positive) or – (negative) sign. The sign represents the type of charge that comes from that end. With lightning this means there is a transfer of a negative charge from the cloud to the ground in negative lightning strikes.
90-95% of all lightning is negatively charged. It is very dangerous and a typical negative charged bolt is about 300,000,000 volts and 30,000 amps of power. Your typical household lighting bulb is about 120 volts and 12 Amps.
(Image credits to NOAA)
These types of strikes only make-up about 5-10% of all lightning strikes. Unlike Negative lightning which originates in the lower to middle of the thunderstorm. Positive lightning originates at the top, some 30-60,000’ feet up. Normally, the ground is shielded from this upper positive charge by negative charges in the central part of the storm; however, when upper level winds are stronger than lower level winds and the storm becomes tilted, or when the anvil of the thunderstorm cloud spreads out ahead of or behind the updraft of the thunderstorm, the ground is no longer shielded from this upper charge. If the charge differences between this upper level charge and the ground become too large, a downward-moving positively charged leader can develop.
Because this strike has to travel over such a large distance it can be up to 10 times stronger and last 10 times longer than a negative strike. So it can reach 1 billions volts and 300,000 amps! The stronger voltage and longer lasting bolt is the reason they cause so much damage and cause so many deaths. Positive strikes are usually the cause of forest fires, house fires and damage to planes and power grids.
They also can travel large distances far away from the parent thunderstorm. Some up to 20-30 miles from the parent storm. While only 10% of lightning strikes victims die from being hit, most are hit by negative strikes. The percentage of positive strike fatalities is much higher.
Some interesting properties of positive lightning: via ( NOAA)
- Positive lightning can be the dominant type of cloud-to-ground during the winter months and in the dissipating stage of a thunderstorm.
- Positive lightning has been identified as a major source for the recently discovered sprites and elves. Sprites and elves are most likely lightning discharges but occur from 18-60 miles (30-95km) in altitude, well above the parent thunderstorm.
- Positive lightning is usually composed of one stroke (negative lightning typically consists of two or more strokes)
- Some studies have found a correlation between tornado genesis and positive lightning strikes spikes. http://www.srh.noaa.gov/jan/?n=local_research_positive_strike http://radarmet.atmos.colostate.edu/steps/positive_cloud/
90-95% of all strikes
5-10% of all strikes
50,000° Hot but last 10 times longer.