SWIFT: Day 8: Got a Little Jingle on a Tennessee Saturday Night…

Good evening readers!

This morning started earlier than expected in Grand Rapids, Michigan. The models and SPC convective outlooks for the oncoming day were looking somewhat promising. Upon this realization, the SWIFT team shot southward with a target area of Southeast IL/Northwest AR. This consisted of the best atmosphere for supercell and possible tornado formation in the nearly country-wide swath of the slight convective risk area. Of note, there were high values of instability in the area and minimal convective inhibition (suppression). Additionally, converse to yesterday, there was sufficient moisture in the atmosphere. However, the failure mode for today was a lack of strong vertical wind shear in the area. This lack of shear gave local wind profiles a less-than-ideal shape, although tornadoes still existed as a possible hazard type.

As we shot through Indiana, we witnessed a line of thunderstorms form along the Mississippi River and Ohio River Valley. While booking down the Midwest, these storms caught up to the trusty steed that is our Chevrolet Express. During this, the team encountered a storm with hail exceeding two inches in diameter. Luckily, our driver LCDR Burich slowed so the majority of the hail passed in front of us. While attempting to get ahead of the approaching line of thunderstorms, we ducked into a Pilot gas station while tornado sirens were going off. While this got the team perky, it was without much evidence and no tornado was close to forming in the area.

The weather and logistics team reconvened at this stop, and ultimately decided that the original goal location was no longer in reach. Model runs were increasingly doubtful of tornado formation. This was partly due to storms that formed to the East which organized into a large line and eroded away much of the available instability originally in the area. Additionally, higher values of wind shear were becoming less and less likely due to surface winds that were in the same direction as the upper level winds. Accordingly, there was an increasingly small chance that the original location would have an atmosphere conducive to isolated, discrete supercells. Instead, the team decided to chase along the line of thunderstorms that had formed along the Mississippi River and were traveling North-eastward. This provided the team with great views of the leading outflow boundary, its 50+ mph winds, and difficult driving conditions for our fearless driver Thomas Pearson. After stopping to experience the oncoming outflow boundary, the team decided there had been enough chasing for the day as we nestled into Western Tennessee.

Photos of the outflow boundary and the ensuing storm taken by Samuel “Wise Gamgee” FordDirks.