Superbolts?

[Michael O'Keeffe]

I have read about a superbolt which is basically a wicked lightning strike that is generated from the top of a thunderstorm and is positively charged and can be 100 times more charged than a normal lightning bolt. One report of a superbolt in Illinois that was intense it broke windows and shook houses. It was later found by farmers that a crater 7 feet wide and a foot deep was carved into the ground by the strike. I think it would be quite a sight to see one of these bad boys. Has anyone have an experience or more information on this rare events?

 

[Danny Neal]

Are those the positively charged bolts with no return stroke? Or is that something else? I have see the "bolt from the blue" and they are usually one bright powerful CG with almost no return stroke. I know I wouldn't want to be hit by one of those.

 

[Jeff Snyder]

I think you are referring to a positive lightning discharge. If so, they are not particularly rare, and you've probably seen many of them if you've chased more than a couple of supercells. Positive strikes tend, in a normally-polarized thunderstorm, to originate near the anvil and hit the ground beyond the storm. In a basic sense, the electric structure of many thunderstorms can be thought of as a tripole, with the primary positive charge reservoir near the top of the storm, the primary negative charge reservoir in the low-mid region of the storm, and a smaller positive charge reservoir right near cloud base. Positive strikes tend to have much larger current / continuing current -- on the order of hundreds of thousands of amps! Both of these tendencies contribute to positive strikes being a significant fire initiator: a large continuing current + a strike away from the storm and precipitation + tinder-dry vegetation or structures = fire!. I'm not sure I'd give them the distinction of being called "superbolts", since they can be very common in some storms and environments. It is worth noting that some storms have an inverted polarity (i.e. primary positive charge reservoir is in the low-levels and primary negative charge reservoir is in the upper levels), in which case many of the strikes tend to be positive in nature. IIRC, storms on the high Plains have a much higher propensity to have this reversed polarity structure and tend to have a much higher proportion of positive strikes.

As for staccato or not lightning... I'm not sure I've read much about what would cause some lightning discharges to have many subsequent dart leaders vs. being "one and done". I know the storms of June 11-12 (I think) in KS seemed to have a lot of staccato bolts, with only one extremely bright flash that seemed to occur in a 'barrage' manner. I remember an HP supercell chase from 4/21/05 that had similar lightning patterns (a plethora of extremely bright but extremely short lightning discharges). I assume it's largely affected by the amount, density, 'wetness', and distribution of hail and graupel within the storm (as it is, the lightning flash rate tends to be correlated quite well with graupel mass <-10C and mass flux at -10 C, with overall charging largely a function of temperature and liquid water content). Perhaps the staccato vs. not is dependent upon the particular charge density and distribution... For example, a relatively broad charge region with low-moderate intensity (measured as coulombs per cubic meter or something like that) may not have enough remaining charge to produce a dart leader to give the subsequent flashes after the return stroke. So, when charge is transferred during the return stroke, the local electric field is reduced enough to inhibit dart leader formation. However, since the charge area is relatively large, you can have many one-hit wonders in a short period of time. On the other hand, a more compact but intense charge region may have a large magnitude of charge that would allow for subsequent flashes (many dart leaders). Just a guess.

 

[Michael O'Keeffe]

Yes Jeff I have seen my share of positive CGs, some from too close. These "superbolts" however are positive CGs that are extremely electified and powerful what makes them so rare I'm guessing is the intensity. I think the term superbolt was just a clever name to give a description of a lightning bolt that is unusally more intense than most, I mean the first time I heard the term was in the book "Extreme Weather" if anybody is interested or has read it.

 

[Brian A. Schmidt]

I know this doesn't contribute much at all to the discussion but...I just happened to see this thread and it got me thinking about an experience I had one summer at my cabin. I figured someone on here can shed light on this mystery. I was sitting on the tongue of our boat trailer in the basement garage. One of the reasons I was there was because it was pouring outside and I was sitting out the storm. My cabin is on a long peninsula at the 50K acre, 105 mile long Lake Cumberland. It is very hilly and my place sits at about 900 ft. above sea level. For some reason, lightning strikes there are much greater in frequency than anywhere else I have ever been. We had a close strike, one of so many I that have lost count, and something strange happened. I never saw the bolt, but the circuit breaker box on the opposite wall from me popped and shot out a spark. The strangest part was that I felt the trailer tongue vibrating, kind of like a "humming" sensation through my jeans. I still cannot figure out what was going on-- the frame was metal with an enamel coating and the only contact it had with the building was its rubber tires on the concrete floor. I was wearing long pants. At any rate, the trailer had some sort of energy flowing through it. Do any of you know what this would have been? What is the scientific explanation? As I said before, for some reason the area around our neighborhood gets hit a lot. A neighbor's horse got hit and killed one summer, and a year or two later, the neighbor was struck and killed in the same spot in the barnyard!

 

[Shane Adams]

How do you tell the difference between a "normally" intense lightning bolt and a "super" intense one? To my eyes they ALL look deadly powerful.

 

[Dennis Sherrod]

How do you tell the difference between a "normally" intense lightning bolt and a "super" intense one? To my eyes they ALL look deadly powerful.

David Drummond appears to be pretty good at knowing what is particularly intense and what is not. He may be able to provide some good answers.

 

[John Hudson]

Some interesting facts about positive lightning strikes I've gleaned from research for my upcoming book:

-A typical negative lightning stroke's duration is only tens of microseconds, during which it delivers an average peak current of 30-35 kiloamperes. A positive lightning stroke, by comparison, are energized with up to 300 kiloamperes at one gigavolt (one billion volts) and can last hundreds of microseconds. It is the duration of a positive strike that can make it exceptionally deadly, and destructive to property.

-Positive lightning was implicated in the crash of Pan Am flight 214 on December 8, 1963. While in a holding pattern above Elkton, Maryland, the Boeing 707-121 experienced a catastrophic midair explosion, killing all 73 passengers and 8 crew. A total of 99 witnesses on the ground reported a CG strike in the vicinity of the aircraft. The investigation that followed revealed that the reserve tank in the left wing exploded, followed by ignition of the center and right reserve fuel tanks. Damage to the wing's metal skin included a four-centimetre hole that was characteristic of a lightning strike.

-Owing to its extremely high voltage, a positive lightning strike can be deadly well after the storm has passed. People who emerge from shelter after the rain has stopped have been struck by lightning from a storm ten or more miles away. The longest bolts often emerge from the front of a squall line, traveling backwards horizontally through clouds trailing behind the squall line. The longest lightning bolt measured to date was 118 miles long, and occurred in the Dallas-Fort Worth area of Texas.

Exerpt from Rage On the Plains: The Science of Severe Weather

Please excuse the shameless plug!


John

 

[Shane Adams]

Here's my next two questions:

(1) How do you measure the length of a lightning bolt?
(2) How do you do whatever the answer to #1 is in 3 seconds or less?