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We broke for lunch at Bosselman's Truck Stop in Grand Island, hungry for both food and data. A quick download of data was facilitated by a special digital phone booth there which featured a data jack and small table. Over a tuna fish salad sandwich, compliments of Mr. Brown, we analyzed data. After a hasty glimpse at conditions, our initial target remained intact. However, as we drove east on Interstate 70, Keith read deeper into our noon (1700Z) data download.
A surface analysis indicated that winds were veering to the southwest over Central Nebraska.
In addition, the huge cirrus cloud shield that I had seen on the satellite loop early that morning
was now covering much of Nebraska including our location. This was not good. We stopped at
York and decided to go north to Northeast Nebraska as quickly as possible where the noon
analysis indicated backed winds and sunny skies would await us.
By the time we reached Norfolk, winds had veered to the south-southwest and the cirrus shield
above was thick. North of Norfolk, we turned east toward Sioux City, Iowa. As NOAA Weather
Radio in Sioux City drifted in on my HAM radio, we could hear reports of sunny conditions from
Yankton into Northwest Iowa. Just west of Sioux City, we crossed over a wind shift line and
stopped. It was apparently a local outflow boundary from a morning storm that tracked through
the county based on old warning statements we read in our data. Winds were easterly at about
5 kts. there. A small towering cumulus grew overhead. For a few minutes, we were excited.
Things looked promising. But then the tower collapsed along with our spirits. We continued to
ward Sioux City and our original target.
It was late afternoon when we stopped on the west side of Sioux City, to view a lifeless sky.
What was going on? There should be storms by now, we thought. I called fellow chaser and
friend Jason Jordan at the National Weather Service Forecast office in Ft. Worth. Jason relayed
information about building storms well to our north in South Dakota. Meanwhile, Bill was monitoring an AM radio station in Yankton. A tornado watch had been issued north of Sioux Falls, South Dakota. It would be a stretch to reach it by dark but we had no other choice. We had traveled far on our quest. We couldn't give up now. So, it was north to Dakota!
Based on information gathered from the AM radio station in Yankton and from Jason, we decided on a target area near Mitchell, South Dakota. Two, then-existing thunderstorm cells would merge there about the time we expected to arrive. The southern storm was moving east, while the northern of the two was tracking southeast. It was after 6 p.m. now, so it would be tough to make it there much before sunset. That was until we realized that the sun would not set until around 9 PM! Finding this out was a jump-start for us. We continued to monitor the radios as we passed by the Gateway 2000 computer factory painted up like a giant Holstein, and located in a pastoral meadow alongside the blue waters of the Big Sioux in North Sioux City, South Dakota.
While on Interstate 29, south of Sioux Falls, Jason Jordan relayed updated information which indicated that the two previous storm cells had fallen apart. Still, the Mitchell target seemed as good as any. We stuck to it.
As we entered the Sioux Falls area, we could make out a sharp anvil edge overhead. We turned west on Interstate 90 toward our target area. The southern edge of the anvil was directly overhead, with pulse waves evident, and paralleled the east-west Interstate. Our mission now was rather simple. We would follow the anvil westward to the storm it was anchored to.
We exited the Interstate at US Highway 81 near Salem. The anvil edge had led us to the southern-most cell in a line that stretched northward. Our plan was to turn west down Highway 38 toward Spencer. However, we missed the turn in Salem and continued north about a mile and pulled over on Highway 81 to view the storm. Winds at Salem were south-southwest at about 5 kts. Our storm displayed decent, but slightly mushy towers. I was not impressed. Soon, I spotted a small and newly-developed anvil just to the west of the convection in front of us. A brief moment passed and a tornado warning was issued. Radio reports indicated that the tornado was moving in our direction. Should we wait for it to come to us? Bill didn't like that idea. So, the decision was made to go west on 38, our original plan.
I had never chased a storm in the Southeast South Dakota area before. I was impressed with the terrain. It was very much like South Central Nebraska, in the Hastings area, for example. Gently rolling, mostly flat topography, with only scattered trees and an excellent, section road network. The countryside was occupied mainly by corn fields and pastureland.
As we headed west on Highway 38 from Salem, Keith exclaimed that he could just make out striations in our newly-discovered western storm. A few miles more and we could see a lowering nearly touching the ground just to our west-northwest. At least that's what it looked like. An area of trees just to our right was obscuring our view to the ground. We cleared the trees and the "lowering" turned out to be a fully-developed tornado! We cleared a small hill and pulled over at a flat, treeless area 4.4 miles due east of Spencer on Highway 38. Bill and Cheryl continued west a few hundred yards further.
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