Storm Highway by Dan Robinson
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Storm Highway by Dan RobinsonClick for an important message
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                   Tuesday, June 15, 2010 - 11:48PM CDT

6/15 SC IL close lightning/severe storms

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HD EXPEDITION VIDEO: Close lightning and severe storms in Fayette/Clay Counties, IL
HD EXPEDITION VIDEO 2: Advancing gust front timelapse

Chased along the I-57 corridor between I-70 and I-64 for the first time today. With some deep layer shear, several outflow boundaries and strong instability, supercells were likely across the I-70/I-64 corridor on Tuesday. Storms began firing on two boundaries almost directly over New Baden, so I was able to start the chase from home. A storm southwest of New Baden became dominant, and I followed this storm east-northeast most of the day. Here is its appearance from New Baden to Albers:

click to enlarge:

After this, I followed the storm from Germantown to northeast of Carlyle Lake without stopping for photos, as it was not doing much at this stage. At St. Peter, a rapid-fire CG barrage as my storm quickly intensified was the highlight of the day - including several close strikes, one within about a tenth of a mile with the ground connection points visible.

click to enlarge:

I could watch close lightning strikes all day - they are my favorite storm phenomenon by far. The closest strike here was a textbook example of a 'split channel' flash, with two return stroke ground connections sharing a common channel partway to the ground. You can see that the low-level branching from the second stroke indicates a new stepped leader was generated from the divergence point down to the ground (no branching occurs above the divergence point on the second stroke):

On the video, you can see what causes the second return stroke to have to produce a new partial stepped leader. There is a longer-than-normal time gap between the return strokes, which causes the channel to decay. Normally, the return strokes are rapid-fire, with the time gaps between them small enough that the original channel stays conductive for subsequent strokes (via dart leaders) to use all the way to the ground. When channel decay occurs due to excessive time between strokes, the dart leader may hit a non-conductive channel mid-descent, at which point it converts to a stepped leader that forges a new path to ground.

The lightning barrage continued for the next 30-40 minutes, but sadly I was not able to stop to shoot any more of it thanks to the upper support kicking in - causing the storms to accelerate eastward. I could barely stay ahead of the storm, stopping to shoot video would have allowed it to quickly bury me in precip. Furthermore, I discovered that the roads/terrain to the east of I-57 deteriorate significantly into curving, hilly, gravel-slickened, deep-pothole ridden roller coasters. The allowed my storm to get far ahead of me and out of range for further intercepts. A sudden, unsigned bridge closure at Ingraham was the final blow to the pursuit of the storm. The images are of the storm between St. Peter and Ingraham:

click to enlarge:

The main squall line was quickly approaching from the west, so I set up for one final pre-storm shot and let the line overtake me. In the second video above, you can see an area of tight rotation along the leading edge of the gust front that passed nearly overhead.

click to enlarge:

After I was clear of the line, I set up near Clay City facing east for anvil crawlers, but there was not much of a trailing stratiform lightning show. Some weak mammatus was the last subject of the day:

click to enlarge:

Dan... I just found your "Open Road" series. I travel I-79 US-19 I-77 US-52 I-40 almost as much as you have. I grew up in Pittsburgh and have lived in North Carolina for the past 25 years. I enjoyed your Open Road Parts 3 and 4. Very familiar to me.
- Posted by Pete from North Carolina

does running in a storm attract lightning?
- Posted by kayla

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