The Mullen, Seneca and Thedford, Nebraska Tornadoes
June 4, 1999
I started this chase from Hays, Kansas with loose knit group of chasers including Alan Moller, John Monteverdi and Mike Foster. We were in separate vehicles, but kept in contact via ham radio on 146.520 MHz.
We drove north to the Kearney, Nebraska library where we checked current weather conditions and forecast data in their Internet room (they have a nice facility). Forecast models indicated that by late afternoon vertical wind shear and surface conditions should be most favorable for tornadoes over southwestern Nebraska. A surface low was forecast to intensify during the day over northeast Colorado, improving shear by backing (causing the wind to change from southerly to southeasterly or east-southeasterly) and strengthening the surface winds. We expected convection to initiate northeast of the low on the high terrain of northeast Colorado and then move into southwestern Nebraska, near McCook. We were somewhat concerned about the warm 700mb temperatures forecast for Colorado and the associated capping inversion, but felt that storms still had a good chance of forming as moisture flowed upslope into the area.
Another factor that has proven to be an important forecast tool for past tornadic events and had been a very important indicator during the last week or so was the location and movement of "dark channels" on the water vapor imagery. For the past several days, tornadic storms had formed at or near the nose (leading edge) of these features. Satellite imagery showed a dark channel moving toward northeastern Colorado and western Nebraska.
We left Kearney and headed west. I separated from the group west of Kearney and took a slightly different route, mainly to explore. I drove west and southwest toward McCook. As I passed through Arapahoe, I could see a young anvil streaming east-northeast from a thunderstorm located NW of McCook. The chase was on!
A side note - a weak earthquake had occurred the day before in southwestern Nebraska (magnitude 3.7 or so). As I drove west from Arapahoe toward McCook, I encountered a broken seam in the road between two slabs of concrete. Several large pieces of concrete lay broken in the highway. I didn't see the damaged pavement in time before hitting one of the large chunks, which broke one of my van's rear shock absorbers. Although the damage was not enough to end the chase, it did make driving a little more difficult. (I don't know if the broken seam was caused by the earthquake or by the hot late-spring sun, but I'll blame the earthquake for now.)
I quickly filled the gas tank in McCook. As I drove north from McCook, I could hear broken bits of communications between Al and the group on the ham radio. They were about 20 miles to my northwest and were already intercepting the storm. At the time, it appeared that there was one main updraft on the western end of the anvil. The anvil appeared to be streaming off to the east-northeast, but the storm was moving almost due north. I was unhappy with myself for separating from the group, but later this would turn out to have been a big advantage.
As I drove north, I could hear the group approaching Ogallala. They were near the updraft and were commenting that it looked like it was going downhill. I continued to drive north toward North Platte.
Warnings were being issued via the NOAA Weather Radio (NWR) frequently. And oddly, warnings were being issued for the county north of North Platte. Due to haze, I could not see the other storms east of what I had assumed was a single thunderstorm updraft on the western end of the anvil.
As I drove north from North Platte, I contacted the Ball State University storm chase team on 146.520 MHz. They were driving north on 83 and had been given a radar update via phone. They described three main storms, the one on the west end of the anvil and two more, one to the north-northwest and one almost due north of North Platte. I decided that I would continue north on highway 97 toward Tryon, mainly because the anvil appeared to be darker and thicker in that direction. (I assumed that a strong updraft was located under the thicker part of the anvil.)
As I drove deeper into the shadows under the anvil, rock hard towers slowly emerged from the haze.
I would find out later in the evening that Al and the group had given up on their storm because it was weak and didn't appear to be capable of producing tornadoes. Fortunately, I continued north on 97 and intercepted the second and later the third storms in this complex. These storms were moving into more moist and unstable air that was being drawn in from the southeast, flowing around the northeast side of the northeast Colorado surface low. I was to see and video at least six tornadoes over the next several hours. (There could have been more!) This is where the images begin, between Tryon and Mullen, Nebraska.
|Looking north-northeast (NNE). Howie Bluestein and
his doppler radar was set up and operational in a field, a safe distance off the road.
These images are video freeze frames that were digitized using a Snappy box. The original video was shot on high quality mini-DV format. Video of this event is available through Storm Stock.
|Looking NNE. Shortly after passing Howie and his crew, the first shallow but rotating wall cloud came into view.|
|A few more miles down the road I met Gene Rhoden. Gene was measuring hail size. The stone pictured measured just under 2 inches across its long axis.|
|Looking north. Another wall cloud quickly formed north-northwest of the first and produced a brief funnel.|
|Looking north. The funnel persisted for a few seconds, but the wall cloud was temporarily undercut by outflow. Gene jumped in his chase vehicle, a well outfitted Ford Explorer, and drove north to get a better view.|
|Looking east. The wall cloud quickly reorganized, began to wrap and produced a swirl as rotation intensified.|
|Looking east. Another funnel formed at the center of the circulation, but no debris was seen beneath it.|
|Looking east-southeast (ESE). As I was watching the wall cloud above, Gene alerted me to yet another funnel.|
|Looking NNE from the same location at the funnel Gene had seen.|
|Looking north. The storm accelerated north. As we approached Mullen, we saw several hail stones in and at the side of the road that were estimated to be greater than four inches in diameter! In Mullen, most of the hail was two inches or less in diameter. I called 911 while still south of Mullen to report the giant hail.|
|Looking ENE. In Mullen, we turned east on highway 2. The rain free base (RFB) and associated wall cloud had enlarged considerably. A large funnel quickly developed under the base, just above 1999 in the image. I called 911 again to report the developing tornado.|
|Looking east. A few miles east of Mullen, I passed the NSSL Doppler on Wheels (DOW). Note the dark clouds overhead. That was the flanking line which extended south from the wall cloud pictured above. Also note the sunlit flank to the distant east. The eastern flank would quickly evolve into a cyclic-tornadic supercell.|
|Looking north at the dissipating tornado produced by the first flank. It appeared that there may have been a larger tornado just to the north of this funnel. However, it was distant, contrast was poor and the lightning didn't provide the needed illumination, so I couldn't say for sure.|
|Looking north. Contrast was enhanced by lightning when this image was taken. The base had lifted and if there had been a larger, perhaps wedge class tornado, it had dissipated.|
|Looking east. The eastern flank continued to grow and intensify. Note that the RFB was fairly flat, but watch as the rear flank downdraft (RFD) developed, the cloud base lowered and a "crease" developed in the towers above the lowering where the RFD was located.|
|Looking ENE as rotation quickly intensified.|
|Looking NNE. Rotation had become violent in only a few minutes. The storm had transformed from a linear flank into two circular updrafts, located on either side of the RFD notch and above the developing tornado.|
|Looking NNE. Lightning illuminated the tornado which was located NNW of the small town of Seneca. I called 911 to report this tornado about the time this image was made.|
|Looking north. Although not easily seen, the tornado was on the ground under these impressive updrafts.|
|As night fell and the storm continued to intensify, spectacular lightning lit up the sky.|
|Looking north from just west of Thedford, lightning arced several miles through clear air underneath the anvil. Note that there were still two barrel shaped updrafts. Time lapse of the video indicated that initially the left member was rotating counterclockwise and the right member was rotating clockwise.|
|Looking NNE on highway 83 north of Thedford. Note the rope tornado barely visible to the left of the highway and the new wall cloud on the right (east) side. Also note the layered appearance of the updraft. I could not determine the sense of rotation at this time, but I assume that a cyclonic (counterclockwise) circulation had developed under the right member of the vortex couplet, or perhaps a new cyclonic updraft developed on the eastern flank of what had earlier been the anticyclonic member of the vortex couplet. Perhaps the DOW data will clarify what happened.|
|Looking NNW at a rope tornado just west of the highway. I assumed that this was the dissipating stage of the tornado that developed near Seneca.|
|Looking NNE as tornado #3 (or perhaps #4) developed from underneath the wall cloud. Since my confidence was low that there was a wedge under the first flank (as described earlier), then we will call this tornado #3. I made my last call to 911 of the evening as I turned north from Thedford to report the dissipating rope tornado and the new developing tornado.|
|Looking ENE as I closed in. The rope tornado dissipated as tornado #3 touches down.|
|Looking ENE as tornado #3 starts to shrink and a new funnel forms to the left.|
|Looking ENE as tornado #3 and tornado #4 were on the ground at the same time.|
|Looking ENE. Tornado #4 dissipated quickly.|
|Looking ENE as another funnel quickly developed.|
|Looking ENE as tornado #5 briefly touched down and then weakened temporarily.|
|Looking east as tornado #5 weakened.|
|Looking east as tornado #5 strengthened and kicked up dirt and debris. The vertical line to the left of the tornado was my van's broadcast radio antenna.|
|Looking ENE as tornado #5 reached maximum intensity. Note the new lowering on the left edge of the image.|
|Looking north at the DOW. They found a break in the sand hills that provided them with an unobstructed view of the tornadoes to their east.|
|Looking ENE. Tornado #5 dissipated as tornado #6 was forming.|
|Looking ENE as tornado #6 reached maximum intensity.|
|Looking ENE as outflow began to undercut tornado #6. This marked the end of visible tornadoes produced by this flank. Outflow undercut the flank, but another flank formed farther east. I stopped and set-up the video and 35mm still cameras beside the road to photograph lightning. As I watched the fireworks, a large lowering, or perhaps the largest tornado of the evening was occasionally visible under the new flank to the distant ENE. Unfortunately, lightning illumination was not well placed and only provided a few brief glimpses of this feature.|
|Looking NE at the multiple flank structure of the storm complex. Low hanging wall clouds were occasionally seen at the focus of these flanks, but no more tornadoes could be confirmed. The lightning display was awesome, but consisted almost entirely of "zits" (short branched cloud to cloud lightning strokes that radiate from where the storm towers enter the anvil). In-cloud lightning discharges were continuous with occasional explosions of extremely brilliant but amorphous single in-cloud flashes.|
A Few Closing Comments
As the evening progressed, this chase evolved into a night-time chase. Chasing in general can be dangerous for inexperienced people, but chasing at night can be particularly dangerous. Proper precautions must be taken.
A chase crew that provided video to a national cable network station, rushed under the updraft to video the rope tornado (tornado #2). By doing so, they entered an area where large hail was falling. Their windshield was broken. By staying back and respecting the power of the storm, I avoided damage while still seeing and videoing all of the visible tornadoes. I may have not been as close, but my windshield was still intact and unbroken at the end of the chase.
I do not recommend night-time chasing to anyone, especially in a remote area like the sand hills of Nebraska. It has taken years of experience as a SKYWARN spotter and storm chaser to give me the confidence and ability to chase tornadic thunderstorms at night with minimal risk. You must maintain an acute awareness of the storm as it develops and changes over time. You must always watch your back for new upwind development or backbuilding and be ready to exit the area quickly to escape danger. (There's no place to find cover in the sand hills.)
Hail is the most likely threat (recall the four inch diameter hail that fell south of Mullen), but tornadoes do occasionally form unexpectedly from beneath the flanking line. And, if you are foolish enough to venture under the mesocyclone and into the bear's cage at night, remember that many significant tornadoes are accompanied by what I term "parasitic" tornadoes. Parasitic tornadoes typically form near the edge of the main mesocyclone circulation, an area that often exhibits extreme and chaotic shear. Parasitic tornadoes are typically ropelike and much smaller than the main tornado which is normally near the center of the mesocyclone circulation. But parasitic tornadoes can still produce significant damage and either ruin your chase or even worse, end your chase career. While your attention is focused on the main tornado, one of these little devils could sneak up on you when you least expect it.
Above all, watch the traffic. Ordinary people do crazy things when driving near tornadic thunderstorms.
In spite of my many years of experience, night-time chasing still makes me nervous! If you chase at night and feel that you've got it figured out, watch out, because I guarantee that you don't.
I'd much rather see a storm like this during daylight.
Copyright 1999 - Samuel D. Barricklow - All rights reserved.
Video of this event is available through StormStock.
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Last revised: November 29, 2009