On the evening of November 13th, 2023 at 8:06:13 pm EST, a powerful lightning flash occurred in Syracuse, New York. This flash was a high peak current positive cloud-to- ground flash (+CG), and it appears to have triggered a large number of upward positive leaders from taller objects in the surrounding area. Grant deBruin (@NewsCenter9) a producer at NewsChannel 9 WSYR, filmed the flash with his phone from the broadcast station and captured the +CG return stroke channel and 12 upward positive leaders. He also recorded the incredible thunder generated by the lightning.
Chief Meteorologist for NewsChannel 9, Jim Teske (@JimTeskeNC9), shared a frame capture of the upward lightning recorded by Grant on X, and I reached out he to see if I could analyze the video. He and Grant graciously provided the video and the following is a summary of my analysis.
Video Analysis
The storms that developed that evening were due to lake effect enhancement where relatively warm water provides moisture and heat to much colder overlying air creating instability and cumulus cloud development. This development evolved into a cluster of storms that moved over the Syracuse area. Storm electrification took place when rising moisture began to freeze forming graupel and ice particles while still in the presence of supercooled liquid water droplets. Non-inductive charging results when the graupel and ice crystals collide in a riming environment.
When the storms passed over Syracuse, the Syracuse Hancock International Airport was reporting a temperature of 39ºF. The cloud ceiling varied from 6,000 ft to 2,800 ft and there was graupel and rain falling.
The National Lightning Detection Network data, provided by Chris Vagasky, (@COWeatherman), showed five impulsive events associated the flash. Prior to the +CG return stroke, there were three negative intracloud events ranging with estimated peak currents of 4.2, 18.6 and 34.6 kA. These were out of the field of view of the camera (lower left of the figure below).
The NLDN indicated location of a +CG return stroke was directly in the field of view and lined up well using photogrammetry. The distance was 2.51 km from the NLDN indicated position and the camera. It is the brightest channel on the left side of the image. The estimated peak current recorded by the NLDN was 115.8 kA which is more than double the average peak current of a +CG return stroke. Therefore, this was a very energetic event. There was one more cloud event recorded by the NLDN following the +CG return stroke and this also was a negative intracloud event outside the field of view to the left with an estimated peak current of 2.1 kA. The NLDN recorded events spanned 60 ms, however, analysis of the video showed the flash lasted 985 ms (+/- 68 ms) in duration.
Video analysis shows that at least 12 upward positive leaders where recorded in the same video frame as the +CG return stroke. Even though there were no impulsive events recorded by the NLDN corresponding to the upward leaders, the upward visible branching behavior and presence of recoil leader segments confirms that these were positive leaders (Warner et al., 2012, Saba et al., 2016). The +CG return stroke channel persisted in two frames along with four of the upward positive leaders.
Therefore, their durations could have ranged from 2 – 34 ms). One upward positive leader was visible in a subsequent third frame so it had a possible duration of 19 – 50 ms.
The analysis of NLDN data and video recording, suggests that this flash was a case of lightning-triggered upward lightning, where a very impulsive +CG return stroke created a large electric field change resulting in the initiation of upward positive leaders from taller objects. Inspection of the area likely associated with the upward positive leaders showed no dominantly tall objects such as very tall broadcast towers and buildings. There were some taller smoke stacks and trees, but none appeared to extend taller than 100 m which is the minimum height usually associated with lightning-triggered upward lightning during the summer months (Rakov and Uman, 2003).
However, this event is better characterized as “winter type lightning” similar to that observed on the west coast of Japan where warm water in the Sea of Japan creates “sea effect” thunderstorms that move over land and cause both lightning-triggered upward lightning and self-initiated upward lightning from wind turbines (Rakov and Uman, 2003).
As is common in winter type lightning, the charge layers are much lower than those present in summer storms. This is evident by the presence of graupel falling at the time of the flash and an ambient temperature of 39ºF. Therefore, resulting electric field from the lower charge region was likely very strong, and the subsequent positive electric field change (physics sign convention) from the +CG return stroke was correspondingly extremely strong causing the initiation of upward positive leaders from objects much shorter than 100 m.
This case appears to be very similar to that observed by Christy Sharkey (@kristy_sharkey) on Feb 13th, 2023 in Renton, Washington. Although the conditions were very similar, I attribute the upward positive leader initiation on Feb 13th to the negative leader propagation following the +CG return stroke. In this case, however, I suspect the upward positive leaders initiated due to the +CG return stroke rather than the negative leader propagation that likely followed. I make this assessment based on the proximity of the upward positive leaders to the +CG return stroke.
Thunder Analysis
Below is a frequency spectrum analysis of the thunder. You can see a high frequency pulse associated with the lightning as nearby induced current may have flowed through conductive materials nearby the camera causing short arcs in air gaps. Alternatively, short induced streamers and leaders may also have formed nearby at the tips of narrow pointed objects such as tree branches or short aerial towers. I define these peaks as “Zips.” This lightning-induced noise is followed by onset of thunder in about 1 second with two distinct moderate peaks at 1.006, 2.006. During continuation of the initial thunder which I believe was associated with nearby incloud leaders, there were seven high amplitude, short duration “Claps” of thunder. I suspect the 3rd through 5th and possibly the 6th and 7th peak were associated with the high peak current +CG return stroke. Reflections from nearby buildings and the temperature inversion that was present at the time likely resulted in multiple peaks. +CG return strokes tend to not exhibit subsequent dart leader / return stroke sequences, however, they do occasionally occur based on our research (Saba et al., 2016). The similar peaks in Claps 3 through 7 suggests they were from the same source. The first two Claps may have been associated with the -34.6 kA IC event which actually may have been a CG based on the estimated peak current.
In the table below, the high frequency lightning induced noise is classified as a “Zip” and the corresponding video runtime in seconds is shown in the first column. The time differential from the first Zip is shown in the second column for the subsequent “Thunder” and the seven high amplitude, short duration acoustic events that are classified as “Claps.”
The speed of sound was calculated to 333.58 m/s for an ambient temperature of 39ºF. Using this speed and the time difference between the Zip and the acoustic events (Thunder and Claps), a distance was determined. Therefore, based on the delay between the Zips and first thunder event, the distance was 336 m. The Claps ranged from 1,643 m to 3,238 m. Interestingly, the third Clap had an estimated distance the same as the NLDN indicated distance and was one of the louder Claps.
Upon closer inspection of the 2nd, 3rd and 4th Claps shows that these have a closely spaced double amplitude peak, and the spacing of the double peak increases with time. A plot of the runtime versus the time between the double peaks for these three events is shown below. The spacing in the double peaks appears to increase in a linear fashion with time.
In conclusion, I would again like to thank Grant deBruin, Jim Teske and Chris Vagasky for making this analysis possible.
References
Rakov, V. A., and M. A. Uman (2003), Lightning: Physics and Effects, Cambridge Univ. Press, New York.
Saba, M. M. F., C. Schumann, T. A. Warner, M. A. S. Ferro, A. R. de Paiva, J. Helsdon Jr, and R. E. Orville (2016), Upward lightning flashes characteristics from high- speed videos, J. Geophys. Res. Atmos., 121, doi:10.1002/2016JD025137.
Warner, T. A., K. L. Cummins, and R. E. Orville (2012), Upward lightning observations from towers in Rapid City, South Dakota and comparison with National Lightning Detection Network data, 2004–2010, J. Geophys. Res., 117, D19109, doi:10.1029/2012JD018346.