What are the + signs on the 13abc radar?

Positive lightning strikes are uncommon, but more dangerous
Published: Sep. 17, 2021 at 7:15 AM EDT
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TOLEDO, Ohio (WTVG) - Did you notice all the lightning from last Tuesday’s storms? Nearly 4,000 cloud to ground lightning strikes were recorded, but if you watch the lightning icons on the 13abc radar closely, you might have noticed two different lightning symbols. The “+” signs on the radar indicate a “positive” lightning strike instead of a normal “negative” lightning strike. A positive lightning flash originates from the top part of a thunderstorm where there is a positive charge built up, it can also originate in lightning that starts at the ground and forks out into the clouds above. Positive lightning strikes only account for less than 1 out of 10 lightning strikes overall, except in cases of “thundersnow” or behind the front line of severe storms in a summer storm complex when it makes up most of the lightning strikes. So why even show the “plus” sign on the radar? Positive lightning strikes are much more dangerous than a negative lightning strike. In the case where the lightning strike is originating from the top of a storm, the charge must cut through 5-10+ miles of atmosphere to reach the ground, so the electricity content is going to be much higher. The flash duration is longer, and the charge build up is about 10 times higher than a typical negative lightning strike. The electricity can reach 300,000 amperes and 1 billion volts. Many house fires and wildfires are sparked by this type of lightning. These are the flashes that are responsible for the “bolt from the blue” when a lightning channel can travel up to 25 miles horizontally away from a storm and strike the ground where the sun is shining. There is also research showing a rapid increase in positive lightning bolts might be a warning sign of a developing tornado if other factors are present.

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