Chase Log: August 26th, 2016 Perry Lake, KS Supercell

A local chase day only three days after my first tornado resulted in some good HP supercell structure and some nice rainbows on the way home. A line of storms with embedded supercells developed in Northeast Kansas and moved northeastward, and I chased one embedded supercell from just north of Topeka, Kansas to north of Oskaloosa, Kansas. While the storm was never severe or tornado warned, it had some textbook HP supercell structure, and I was quite satisfied with my chase.

During the morning of the 26th, I was keeping a close eye on things, as the SPC had a Slight Risk of severe weather with a 2% tornado risk for Northeast Kansas. They had mentioned it may need to be upgraded to a 5%, and in the early afternoon, a Tornado Watch was being considered for the area. After 3 pm, storms were firing north and west of Topeka. However, none looked very promising, and I waited until a good storm developed. Around 3:30, a supercell formed from a complex of cells just northwest of Topeka and had reports of a wall cloud. I took off northward, intending to intercept the storm northeast of Topeka near Meriden, Kansas.

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~3:45 pm, just north of Topeka, Kansas. A shelf cloud signifies the rear-flank downdraft of the storm. Behind this shelf is some very heavy rain.

I drove northeast towards Meriden and positioned myself in front of the mesocyclone. The supercell had started to become embedded within a larger line of storms, so it took on HP characteristics and the rear-flank downdraft became clouded with rain. However, the wall cloud was still visible.

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4:05 pm, south of Meriden, Kansas. The wall cloud is in the center of the picture, with the rain-filled rear-flank downdraft to its left. While present, the wall cloud was not particularly impressive, and only had mild rotation at this point.

As I entered Meriden, I parked in a parking lot and waited for the storm to come to me. The wall cloud passed less than a quarter mile to my northwest, and had moderate rotation visible. If a tornado had touched down, it would have been very close to my location. The rotation passed to my north and the rain of the rear-flank downdraft swept through Meriden. The rain made it quite difficult to drive, and often I had to slow down to less than 50 mph on the highway. I decided to head north and east more, to get ahead of the storm once again. I escaped the rear-flank downdraft as I crossed Perry Lake, and headed towards Oskaloosa, Kansas.

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4:38 pm, west of Oskaloosa, Kansas. The wall cloud is again in the middle, with the rear-flank downdraft behind it and to its left. The wall cloud is not particularly impressive here either.

Interestingly, not long after this picture was taken, the wall cloud became larger, and a well-defined tail cloud developed. I thought things might get interesting here, but after about 8 minutes, it fell apart as I entered Oskaloosa. I continued a little north of Oskaloosa, but as the storm caught me, I decided to call the chase and headed back to Topeka.

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~5:15 pm, Topeka, Kansas. As I came home, I spotted several impressive rainbows, with this one east of home the best. A double rainbow is occurring here, with the bottom one very easy to see, and the top one barely visible.

I had some higher expectations for this day, but even though there was no tornado, some good HP structure and a display of rainbows more than made up for it.

Some Meteorological Analysis

The tornado threat seemed pretty good to me in the early afternoon. While storms were expected to eventually form into a line, early in storm evolution the tornado potential seemed fairly decent. There was 40 kts+ of 500 mb flow, with a surface low near Manhattan, Kansas and a warm front extending from the low southeast towards Kansas City. The supercell was in an environment of ~2000 SBCAPE, 40-45 kts bulk shear, but only ~150 SRH. The lack of low-level shear may have stopped the tornado threat. It seemed to me that storms may have initiated too early, thus going linear too quickly. Had the storms initiated later, and remained discrete later when low-level shear increased, there may have been tornadoes. To this point, as the line of storms moved into Missouri, the supercell I was chasing remained embedded in the line and produced a couple tornadoes south of Cameron, Missouri. An interesting case.

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