ZT Research

Toronto CN Tower Upward Flash, 5/29/11

2011-06-02T09:08:00.003-06:00

I came across an very nice upward flash captured by Richard Gottardo on 5/29/11 from the CN Tower in Toronto Canada. Although I cannot verify the sequence since there is no video, I suspect the ground flash to the right is a positive ground flash that triggered the upward positive leader from the CN Tower. Recoil leader activity is visible in both the suspected triggering flash and the upward leader suggesting they were both positive polarity. This is the typical pattern observed in Rapid City, SD.

Toronto CN Tower Upward Flash, 5/29/11

Disney Magic or Upward Lightning? 3/21/11

2011-03-21T10:55:00.002-06:00

Dan Robinson found this YouTube video which shows the Tower of Terror being struck by lightning in Disney World Florida on 9/12/10. One frame shows a second upward branch suggesting this was an upward flash that might have been triggered by the flash activity that is visible in the preceding frames. Either way, I am sure it got everyone's attention on the ground.

Are thundersnow events mostly tower-initiated upward lightning?, 2/1/11

2011-02-01T13:42:00.005-07:00

I am currently watching the big middle US blizzard move from Oklahoma City towards Chicago. My lightning data feed shows occasional ground strokes and cloud flashes well into the snow sector along the I-44 corridor. I have been plotting these events on Google and for the events that have a small location clustering (i.e., 2 km diameter), they plot right on top of a visible tower. I suspect that these are all upward lightning flashes that self-initiate from the tower. The ground strokes and cloud events recorded by the lightning location system are either subsequent recoil leaders that form on weak branches and connect with the main upward leader channel or dart leaders (i.e., recoil leaders) that form after current cutoff and connect with the tower tip; both of which produce an impulsive return stroke that is detected by the location system. In Rapid City, most of the upward flashes that I observe are triggered by a nearby preceding positive ground flash. I am not seeing any preceding flashes for these cases. This is likely due to the lower cloud base (i.e., lower charge region) and the intense electric field produced in heavier snow. Given the data shows negative events (negative charge lowered to ground), the lower charge region influencing the towers is likely negative resulting in an upward propagating positive leader from the tower.

So a fundamental question comes to mind. Are most of the lightning events recorded during strong snow storms upward lightning from tall objects? If so, what is the percentage? If indeed most "thundersnow" is caused by tall structures, are we in essence creating more lightning by building tall towers and buildings?

I plan to investigate and address this in the future. Stay tuned.

Another Possible Cause for "Snaps or Clicks" Heard During Lightning Flashes, 12/27/10

2010-12-27T19:39:00.002-07:00

A colleague sent me an article that addresses another possible cause of clicks or snaps heard during a close lightning flash prior to thunder arrival. The article proposes that sound can be created through the transduction of electromagnetic energy at audible frequencies to vibrations at those same frequencies in nearby objects. Essentially, the electromagnetic pulse from the current change in the lightning flash would travel at the speed of light to nearby objects. These objects, such as cars, fences and even dry vegetation would act as transducers and convert the electromagnetic energy into acoustic energy (i.e., sound). This acoustic energy would then travel at the speed of sound and be heard by video equipment or the human ear. This may also be the mechanism behind reports of sounds associated with meteors and aurora.

In the clip shown in the previous post, there does seem to be two audible snaps that correspond to two bright light pulses from the close flash. The matching of audio amplitude with the light amplitude would support the emission and conversion of electromagnetic energy to sound energy.

Here is the citation of the article.

Coleman, Timothy A., Kevin R. Knupp, John T. Tarvin, 2009: Review and Case Study of Sounds Associated with the Lightning Electromagnetic Pulse. Mon. Wea. Rev., 137, 3129–3136.

The article does also mention the alternate idea of the sound being created by corona from nearby objects as a result of the rapid electric field change generated by the close flash.

Close Lightning Strike in Darwin, Australia with an Audible pre-thunder "Snap" 12/25/10

2010-12-26T08:27:00.007-07:00

A friend sent a link of a close lightning strike near Darwin, Australia captured yesterday (12/25/10). You can hear an audible snap during (or very close after) the bright return stroke and prior to the thunder reaching them. This was likely a short upward leader that was very close to them that failed to connect with the downward moving leader. The snap is weak thunder that is created by the short and much less energetic upward leader that fails to connect. Given that you can hear it and that it is so close to the return stroke in time means that it was extremely close to the cameras. If it had connected, the return stroke would have likely have been within a few meters of the photographers.

There appears to be a barbed wire fence in the foreground near the tripods. Another possibility is that the snap is a short spark or audible corona or current flow that was induced in the fence by the nearby flash. I have heard this when filming near powerlines, but this usually sounds more like a zipper or buzz rather than a snap.

It is also very interesting to see the puff of smoke or dirt that kicks up where the connection is made.

Here is a direct link to the YouTube video.

Continued Quiet Pattern for August, 9/1/10

2010-09-01T08:21:00.002-06:00

August was also unusually quiet with no upward lightning observed. Most activity remained north of the area with northwest South Dakota and the northern Black Hills experiencing numerous storms. Operations will officially terminate for the season on 9/10/10.

There were a couple of small, weak storms that moved through the area, but these were not conducive to upward lightning. However, I was able to capture a nice timelapse as one of these storms approached and moved over.

Quiet July, 8/2/10

2010-08-02T09:30:00.004-06:00

After a very active June, July has produced no observed upward lightning flashes. I spent the last part of July at the Kennedy Space Center hoping to film lightning over NASA's array of electric field instruments. However, only a few storms formed as the weather pattern was hotter and drier than typical. A handful of captures were made from storms on the edge of the research domain. Monsoon moisture has made its way to the northern plains, and coupled with periodic upper level shortwaves, is providing a near daily chance for thunderstorms during this first week of August.

Highly Branched Upward Lightning, 6/22/10

2010-07-03T09:29:00.002-06:00

Two highly branched upward lightning flashes occurred on the evening of 6/22/10. Below is one of the flashes captured at 1,000 images per second.

Midnight Upward Lightning, 6/20/10

2010-07-03T09:13:00.003-06:00

Captured four upward lightning flashes to the towers in Rapid City, SD. The first flash was captured while driving to the observation location and video captured at 1,000 images per second is shown below.

Multiple Upward Lightning Flashes, 6/16/10

2010-07-03T09:07:00.003-06:00

An amazing eight upward flashes within 30 minutes took place in Rapid City, SD during the evening of 6/16/10. One upward flash had simultaneous upward leaders from seven towers. High-speed video was captured from two locations and at recording rates as high as 67,000 images per second. Below is high-definition video.

Below is the same flash recorded at 9,000 images per second.

Four Tower Upward Lightning Flash, 6/3/10

2010-06-05T09:51:00.002-06:00

Captured a four tower upward lightning flash on the evening of 6/3/10. The four upward leaders were triggered by a nearby positive ground flash. The video below was captured at 1,000 images per second. The triggering flash was to the right of the screen and precedes the upward leaders. One leader was very bright and strong exhibiting no recoil leader activity. The second brightest leader was dim and weak and exhibited extensive recoil leader activity. The remaining two upward leaders were very dim but visible on the other high-speed cameras.

Four Upward Lightning Flashes, 5/24/10

2010-05-29T23:44:00.008-06:00

Captured four upward lightning flashes around 130 am on 5/24/10. The first three where from the KEVN tower and the last was from the KNBN tower. All were single upward leader flashes.

Storms To Develop in the High Plains, 5/21/10

2010-05-21T17:34:00.002-06:00

Storms are expected to develop in the Black Hills and Rapid City area this evening. The weather pattern will be favorable for storms for the next several days and into next week.

First Storm of the Year, 4/13/10

2010-04-13T23:50:00.002-06:00

A broken line of storms moved over Rapid City around noon today. There were a few flashes both north and south of the primary towers, however, no high-speed captures were made as these flashes were out of the field of view.

2010 Gameplan

2010-04-12T16:43:00.005-06:00

We are gearing up for the 2010 storm season. The four sensor sites are up and running with improvements in instrumentation planned for sometime in May. The primary camera vehicle "The Lightning Rod" will be joined by a second vehicle "The Ground Rod" that will be used as a second camera platform as well as a semi-mobile electromagnetic sensor site. The Ground Rod will be stopped and grounded when making electromagnetic observations. This vehicle (Chevy Silverado 1500 Crewcab 4x4) is still undergoing modification and will hopefully be fully operational by the end of May.

I will occasionally be streaming live video during my research operations and when chasing/spotting away from our primary research area. I have embedded the live stream in this blog at the end of the posts.