Tornado Diaries: April 9th, 2011

Most meteorologists recall a moment in their childhood that fostered their obsession with weather. My moment was in second grade, when a severe thunderstorm hit my hometown while school was in session. I vividly remember classmates being frightened, while I sat in the school’s basement thinking the situation was pretty sweet, to use with the parlance of a second grader. After that day, I was hooked on severe weather, and although that specific event did not spawn a tornado, I remain fascinated by them to this day.

Many years later while attending Iowa State University in Ames, Iowa, I had opportunities to travel across the Midwest during spring and summer, in search of the elusive and dangerous tornado. There are three specific storm chases I will be detailing this spring, the first of which occurred on April 9th, 2011.

Lost in the shuffle of an incredibly active 2011 severe weather season, April 9th, 2011 was one of the most significant tornado outbreaks in Iowa history, with 22 twisters tearing across the northwestern portion of the state. Most of these tornadoes were spawned by a single thunderstorm, which myself and seven other meteorology students from Iowa State tracked for several hours. Nine of the 22 tornadoes were classified as EF2 or greater, causing at least significant damage to trees and structures. Those nine tornadoes occurred within a three hour window within the same thunderstorm.

Waking up that morning, severe weather did not seem particularly imminent as temperatures were in the upper 40s and fog was present. Morning low temperatures were near 50 degrees in the target area for storm development. However, temperatures and dew points did not waste time rising behind a strong warm front lifting through the region. Daytime temperatures reached 87 degrees just south of where the first tornado developed, an increase of nearly 40 degrees in less than 12 hours!

April 9, 2011 Mapleton Iowa Tornado Radar
Mapleton tornado radar signature. GRLevel2 Analyst V2.

The weather forecast called for storms to form across far eastern Nebraska in the mid to late afternoon hours before moving into western Iowa. Our group was positioned east of the Missouri River as storms began to build. The plan was to target a storm after it crossed the river so we didn’t have to worry about finding a bridge.

Around 6pm CDT, a powerful supercell moved into Iowa, about 25 miles southwest of a small town called Mapleton. We were now positioned in Mapleton, in avoidance of unfavorable terrain just east of the river. Shortly thereafter, our group left the town and headed southeast to better observe the storm. At 6:20pm CDT, the first tornado of the day was reported near Mapleton. We were in perfect view of the tornado, but did not realize it at the time because of its atypical structure. From our distance, the small bulge from the base of the storm and the dark mass near the ground appeared disconnected. It wasn’t until we reviewed the video footage that night that we realized we filmed the tornado.

Soon, the tornado became rain wrapped and we moved northeast to follow the storm. It felt like the event was short-lived, with the sun setting and the storm struggling to get going again. Just after 8:15pm CDT, as light was fading, our group pulled to the side of the highway, presumably to discuss ending the chase. Typically, we wouldn’t chase at night, as the primary way to stay safe while chasing is to be able to physically see what is going on, and that safety valve is removed after sunset. Since the storm appeared to be weakening, it was an easy decision to abandon the chase and head home.

April 9,2011 Ida Grove Tornado on Radar
Ida Grove Tornado: GRLevel2 Analyst V1, Base Velocity.

Meanwhile, a bright flash of lightning lit up the sky and a large funnel was almost to the ground about three miles northwest of our location. The supercell dropped down another tornado just south of the town of Ida Grove. The next two hours seemed like a blur. This storm put down over a dozen tornadoes, many of which were very large, over a span of  approximately 50 miles. The largest tornado struck near the small community of Nemaha. At 1.5 miles in diameter, this tornado was the widest recorded tornado in the recent history of the state of Iowa (1950-2017). It was this particular twister that forever gained my respect for the danger posed when chasing, and it is the reason I will never again chase at night.

April 9, 2011 Ida Grove Wedge Tornado
Ida Grove Tornado: GRLevel2 Analyst V1, Base Velocity.

Just prior to reaching the town of Nemaha, our vehicle lost internet data. At night, this meant we were 100% blind chasing. There was no way to visually see a tornado other than random lightning strikes, and there was no way for us to see a tornado signature on radar. As a result, we drove east of the town to position ourselves well southeast of the tornado as it passed. Unfortunately, as can be seen from the included radar images, the tornado greatly expanded in size during the period of time in which we had no radar. I vividly remember driving east on the road out of town and completely losing visibility as dirt and cornstalks blew across the road. At the time, we believed we were driving through strong inflow into the storm, as we had been experiencing 60 to 70 mph southeasterly winds. After reviewing the data a few days later, we determined that we were very likely within the outer circulation of the tornado that night. Within 10 to 15 minutes of losing data we went from safely being southeast of the storm to being in an incredibly dangerous situation. I often remind myself of that moment while chasing, as I never want to be in the same position again.

April 9, 2011 Ida Grove Tornado on Radar
Ida Grove Tornado: GRLevel2 Analyst V1, Base Velocity.

We eventually regained visibility after a short period of time and continued driving eastward before pulling over to discuss options with the other car in our group. We headed back to Ames, de-stressing while processing what we had seen. The storm did not stop producing tornadoes after we stopped chasing that night, and an EF4 tornado struck near the town of Pocahontas at around 10:00 pm CDT.

Throughout this entire event, not a single person died and only a few minor injuries were reported. This was incredibly remarkable given the strength of many of these tornadoes, and the fact that almost all of them occurred after sunset. Part of the reason was likely the rural tracks of these storms, however National Weather Service warnings that night were also timely, especially for an area with poor radar coverage.

While not my introduction to severe weather and storm chasing, April 9th, 2011 was the day that gave me a true appreciation for the incredible power, unpredictability, and extreme danger of tornadic thunderstorms. Although we did make some poor decisions that evening, I can look back on the event fondly, as much was learned and the event didn’t take a single life. April 9th was a gateway into storm chasing that I’m still walking through to this day, and two more posts will follow, documenting these chases. The next post will cover May 18th, 2013, where a violent tornado tore through the rural landscape of southwestern Kansas. Until then, I hope everyone stays safe during this very active severe weather season. Keep a watchful eye on the sky.

 

Catch Bryce’s next tornado chasing experience here.

 

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