How does lightning form?  Does it strike up or down?  Over the decades I’ve seen lightning do some freaky stuff.  In this visually stunning video we’re going to explore and explain the weird world of lightning. 


Thunderstorms have the ability to separate pools of positive and negative charges in and around them, thus creating powerful electric fields.  Lightning is born between two oppositely charged regions as a network of electrically conductive channels called leaders materialize and begin to tunnel a path through the poor conductive air in between. Think of leaders as a sort of jumper cable. The leaders branch out in two directions, each with opposite polarities toward both regions in an attempt to neutralize the charge separation.

Most lightning flashes occur within the storm and are called cloud flashes or intracloud lightning. 

GROUND FLASH or Cloud-To-Ground Lightning
When one end of the bidirectional leader network connects to the ground or object on the ground we call it a ground flash, or cloud-to-ground lightning. CG for short.  

In the most common CGs, a negatively charged step leader approaches the ground. The electric field between the step leader and the ground strengthens to the point that an oppositely charged positive leader (aka upward streamer) begins reaching up bridging the gap between the two. More than one upward leader may initiate and attempt to connect with the downward leader, however, the first to reach a downward propagating step leader will suddenly complete a channel path through the resisting air for the flow of powerful electrical current between the Earth and cloud. Electrons then RAPIDLY accelerate down the channel causing extreme heating and the brightest flash of the event.  This is the return stroke of negative CGs.  In rare photographs, you can see failed upward connecting leaders that didn’t reach, the downward leader first, and thus terminating into the air. 

the air around lightning becomes So hot that it explodes as a supersonic shock wave that transitions to an acoustic wave within a few meters. This rapid expansion of air molecules creates sound waves that radiate outward about 1 mile every 5 seconds.  The sound we hear is thunder. 

Often after a negative CG return stroke, multiple other return strokes follow causing the main channel to flicker.  This is called a multistroke CG flash.This repetitive nature is caused by recoil leaders forming on the upper end of the lightning channel in the cloud which is positive polarity. 

The return stroke of typical positive CGs rarely flicker. Many occur between a positive pool higher in the thunderstorm, and the ground.  Because of the greater distance the leaders have to blaze through the resisting air, the return stoke of these positive CGs is often much hotter, brighter and longer in duration. The peak charge in Positive CGs can be 10 times more powerful than a typical negative CG and thus considerably more dangerous. These are generally the most powerful CGs, reaching temperatures up to 30,000 Celsius. That’s roughly 5 times hotter than the surface of our Sun.  Positive CGs only account for about 5-10% of all ground flashes worldwide, But In tornado Alley, they are an atypically common sight. I tend to see them just downstream of strong storm updrafts.  

Sometimes a bolt of lightning can leap miles away from a storm jolting earthlings with surprise. 
We call this a Bolt from The Blue.  Outdated paradigms suggested these clear air channels leaping out the back of storms were positive in polarity.  But the latest research using lightning mapping and high speed cameras have shown most of these startling zaps are indeed negative.  
If you capture a Bolt from the Blue and it has a lot of branching, chances are it was a negative CG instead of a positive.

Sometimes storms can grow upscale into massive complexes stretching across states.  These systems can have horizontally layered charge regions that serve as the conduit for lightning to travel over a 100 kilometers.  They transfer HUGE amounts of charge, and cause abrupt changes in the electric field,  which can trigger another flash in a sort of domino effect.  Upward lightning travels UP from tall objects on the ground into the storm.This is ALSO called Ground-to-cloud lightning.  Almost all upward moving flashes are triggered by a nearby lightning flash, either when leader activity or a return stroke occurs close enough to the tall object causing an abrupt change in the electric field. .  

This video was possible thanks to lightning scientist Tom Warner’s research. For more in-depth information visit his website