Nebraska 25knt Shear Produces Long Lived 2 Hour Wall Cloud
Chase Account by: Scott Blair
Chase Team: Scott Blair, Kevin Scharfenberg, Jason Politte.
Brief Weather Setup
At 7am, temperatures across the plains were in the low 60's. A dry line extended from Amarillo, TX to Guymon, OK to Goodland, KS. Skies across the Oklahoma Panhandle and Western Kansas were clear. In Holdrege and Grand Island, Nebraska, thunderstorms developed and later fell apart. A cold front extended from extreme Northwest Nebraska into the Dakotas. Winds across the plains were generally south or southeast. Nebraska only had 25knt shear across the area. There was a sharp contrast in temperatures at 850mb near Nebraska as well as some divergence. Lifted index values rose to -4. Winds directed most convective activity to the southeast. By 7pm, temps warmed into the upper 70's across Nebraska as a cold front cut through the state. Numerous storms and a few supercells developed ahead of the front in Eastern Nebraska and Central Kansas. In Central Nebraska, an isolated supercell developed along the front. The closest storm to it was 90 miles away.
We all woke up just before 8am. We started the early morning rituals of charging camera batteries and forecasting. The Weather Channel provided us with a laugh as they were forecasting NO threat of strong or severe weather across the plains. Kevin played with the laptop and started to get weather information. SPC had a slight risk out for areas of NW Kansas and W Nebraska. Of more interest was the Moderate Risk posted for the plains on the Day 2 outlook (May 31). We were excited about the possibility of an outbreak tomorrow, but stayed focused on today's chase. We decided on a target area across NW Kansas into Nebraska. We planned to stop in Colby, KS to decide our next move. Kevin continued to say, "I love day before outbreak chases." We agreed with him as this day would be no exception.
Jason and I fully equiped our chase cars after being slammed with extra hotel expenses with the laptop. Kevin asked the Super 8 lady where a good place to eat was. She directed us down the street to a neat little place. They gave us a good breakfast with more than I could eat. The best part was the total bill, which was under $10. We stepped outside the diner and watched the clear blue sky. It was time for the chase to begin!
We hopped on Highway 54 out of Guymon, OK towards Liberal, KS. At Liberal, we drove north on Highway 83. We passed through Sublette, KS and thought of Al Pietrycha's great video of a tornado there in 1996. We enjoyed the terrain of Kansas and later reached Scott City, KS at 12:12pm. The skies were still clear, but at 12:24pm, the first signs of cumulus were located to the north. Over the next few hours, they grew in number and size. Around 2pm, we reached Colby, KS. We grabbed some food at the local Subway, filled up with gas, and Kevin made a quick call to Oklahoma for brief weather information.
During this period, most of the cumulus began to grow quickly and were located to the north and east of Colby. At 2:13pm, we made our move north on Highway 25. At 2:16pm, we noticed several hard convective towers in the distance about 15 miles ENE of Atwood, KS.
After 30 miles without one town, we reached Atwood, KS. We began to get weather information and watched the sky. A few cumulus clouds were becoming storms towards the far east while clear skies prevailed over the west. No watches or warnings were in effect. At 2:48pm, we decided to make a jog to the east on Highway 36 out of Atwood. We turned on KRVN Lexington Radio (a great wx station) in both chase cars to monitor any future warnings. Around 3:30pm, we pulled off near Reager, KS. We watched the sky start to swell with strong cumulus, still to the north and east. A tornado warning was issued for a county in Central Colorado, but that was too far away to even give it a thought. We chose to trust our target area, so we shortly drove east and arrived in Norton, KS at 3:50pm, and then jumped north on Highway 283 out of Norton.
Shortly after Norton, KS on Highway 283, the situation became active. We reached Southern Nebraska at 4pm as a couple of severe t-storm warnings were issued for the storms to the east and a tornado watch was issued for parts of Western Nebraska. At 4:15pm, we were just south of Arapahoe, NE. The largest storm was 30 miles SW of Hastings or about 20 miles to our east. At 4:35pm, a severe t-storm warning was issued for a storm to the north of us about 15 miles west of Broken Bow, NE or about 55 miles north of us. This storm was isolated from any other storm. At 4:50pm, we had to make a huge decision. Many storms laid across the east with one under a tornado warning. However, they were a good distance away and were pushing away from us. A tornado watch was posted for Western Nebraska with one severe t-storm over that area. However, it would take us a good amount of time to make it there, leaving only one hour of sun. We watched the isolated supercell to the north begin to grow rapidly. We concluded that this storm would be the one.
Just before 5pm, we arrived at Lexington, NE and turned west on I-80. As we drove, it developed with a backsheared anvil and an impressive flanking line. The flanking line had explosive development as the storm began to get well balanced. At 5:20pm, we reached Gothenburg, NE but decided to wait and take the next exit north. The storm was perfect as we could now see a base with a hard backsheared anvil. At mile marker 203, the first signs of a small wall cloud developed. At 5:30pm, we quickly turned off at mile marker 199, the Brady exit.
We headed north out of Brady, NE to still see a small wall cloud under the updraft base. Kevin used his labtop software for road networks. The best road network in the area that would take us to the lowering were dirt roads. We checked the condition of the dirt roads and made sure it had not rained in the area recently and drove ENE towards the supercell. Shortly after taking the dirt roads, the wall cloud dissipated. After a few winding dirt roads, we found a nice ridge with a great view of the rain free base. At 5:40pm, we pulled off the road and watched the beautiful storm. At this point, there was no wall cloud or any other interesting features. It was so peaceful with very few cars and the powerful thunder in the distance. At 5:45pm under the updraft near the precip shaft, a quick funnel developed and slowly dissipated. I should add that this was the first of eight funnels in a 40 minute period (5:45, 6:01, 6:04, 6:10, 6:12, 6:17, 6:20, 6:25). At 5:50pm, small scud began to grow under the updraft base. It became obvious that this was a developing wall cloud. At 5:59pm, the wall cloud completely formed and became better organized.
We quickly reported the wall cloud in to the local National Weather Service. The odd but wonderful thing about the wall cloud was the movement was nearly stationary. It was not moving any faster that 5mph. We considered getting closer, but we had good contrast where we were. The wall cloud went through many different shapes and sizes. It first started out as an inverted pyramid. At 6:15pm, it changed into a smaller shape along with a large tail cloud. At 6:20pm, the wall cloud gained some speed and changed into an impressive slope on the east side next to the precip. After 6:25pm, it moved faster, tightened up, and started to wrap in rain. The rear flank downdraft punched in behind the wall cloud as the clear slot indicated perfectly. An incredible show of the evolution of a wall cloud!
The wall cloud did not dissipate, but we briefly lost it do to bad contrast and rain obscuring the area of interest. We decided to leave the area, and the dirt roads as soon as possible. At 6:37pm, a beautiful but dangerous sunlit hail shaft lurked to the east. The sun also turned the sky dark black to the east. After a few jogs on the bumpy roads, we reached Highway 47 that provided another dilemma. The gas tanks were starting to drop, so we needed to find a gas station within the next 50 miles. Highway 47 proposed two options. "South takes us to gas and the risk of wrapping hail. North takes us clear of hail, but risks the problem with gas." Considering the south route is great for the gas problem and would keep us ahead of the storm, we decided to take it. After a short drive south, we hit some quarter size hail and decent east winds. I decided I did not want to risk a lost windshield, especially with a possible outbreak tomarrow. We turned back around and drove north on Highway 47. At the same time, the National Weather Service issued a tornado warning for our storm in Central Dawson County.
After driving north, we took Highway 40 east and stopped for gas at 7:15pm in Callaway, NE. While we filled the hungry cars up, we shot a few pictures of spectacular mammatus clouds directly above us. The sky was filled with this dramatic sight. As I was shooting my last pictures, Kevin started to yell my name. He told me that KRVN said that "spotters reported several tornadoes on the ground north of Lexington." While this report was probably false, it was worth checking into. We jumped back southeastward onto Highway 40 as more severe weather reports filtered in. Of other interest, many severe supercells in the distance were defined in the east across extreme Eastern Nebraska and Kansas. We needed to jump south soon, considering we could not see the wall cloud thanks to the rain in the way. Luckily, we were still rain free with the exception of a few sprinkles here and there.
The wall cloud became once again visible about 30 minutes after filling up with gas. Around 8pm, we arrived in Miller, NE and took Highway 183 southbound. This would put us ahead of the wall cloud near Holdrege, NE if the storm kept its speed. At 8:05pm, a tornado warning was issued for Phelps County, which was 10 miles to the south. The wall cloud was plenty visible, so if it dropped anything significant, we would see it. By 8:15pm, we crossed over I-80 and moved into Phelps County. The wall cloud was very dramatic. A nice sustained funnel cloud hung from the wall cloud with a mid level funnel to the east of the wall cloud. The situation was becoming hectic, so from this point on, there was no time to shoot stills, only video. At 8:20pm, KRVN broadcasted that spotters reported golf ball size hail near Loomis, only 5 miles to the west of our location. At 8:22pm, the storm produced its most dramatic stage. A violent downdraft near the precip sent a significant dust foot under the wall cloud, resulting in the slow process of the wall cloud becoming outflow dominated.
The storm was coated with strong striations along with perfect contrast, which also produced vivid images on video. We arrived in Holdrege, NE around 8:35pm. The wall cloud was now 2 miles southwest of our location. It was still very dramatic, but as we approached the north side of the city, my chasemobile developed severe problems that actually killed it. As the beautiful cloud moved away on its southeast journey, we had to work out problems with the chase cars. Since my car was dead for good, we luckily had Jason's working perfectly. The sun quickly set so we decided to stay at the Super 8 a block away. We later worked out details and transferred all of Kevin's and my equipment into Jason's chase car. We briefly forecasted and prepared for a Moderate Risk day that was just about a dozen hours away.
A very successful chase day was complete. No tornado, but with a day like this, who could complain? With very weak winds (25knt shear), a long lived wall cloud developed and was sustained for over 2 hours along with 10 funnels that we witnessed! A great day to say the least. --Scott F. Blair