2011–2018: Super Outbreak, cancellation of Storm Chasers, death of Joel Taylor
On April 27, 2011, during the 2011 Super Outbreak, Timmer observed four destructive wedge tornadoes across eastern Mississippi and Alabama, including tornadoes that impacted Philadelphia, Mississippi and Tuscaloosa–Birmingham. At the time, Timmer stated that the severe weather event was "hands down the most unforgettable day", while also describing the amount of tornadoes as "heartbreaking" and "overwhelming". The severe weather event was premiered as an episode as part of Storm Chasers, titled "Tornado Rampage 2011". In the same year, Timmer built the heavily armored Dominator 2, modifying it from a GMC Yukon XL.
Following declining ratings, Storm Chasers, the television series that Timmer starred in, was cancelled in 2012. In the television series, Timmer also followed severe weather with his TornadoVideos.net team in a SRV Dominator vehicle, the team of which consisted of Timmer, photographer Chris Chittick, and driver Joel Taylor. After the cancellation of Storm Chasers, Timmer then starred in another television series, Tornado Chasers. Timmer would then intercept the Arnett–Woodward, Oklahoma tornado which would ultimately result in six deaths and 28 injuries.
A year later, in 2013, Timmer chased an erratic-moving EF3 tornado near Bennington, Kansas, which he recalled as "probably the most powerful, most intimidating tornado that I've ever chased". Three days later, Timmer was injured after chasing the 2013 El Reno tornado for KFOR-TV, which ultimately killed 3 professional and 1 non-experienced storm chaser, including Tim Samaras. While chasing a tornado outbreak associated with the October 2013 North American storm complex in Nebraska, Timmer was hospitalized after suffering a seizure as part of the KFOR-TV weather team. According to Timmer, it was his second seizure.
In the same year, Timmer constructed a third vehicle, the Dominator 3, modifying it from a 2013 Ford F-350 Super Duty pickup truck and weighing 11,000 pounds (5,000 kg). He chased his first tornadoes inside the Dominator 3 near Shawnee, Oklahoma in May that year. Additionally, in 2013, he became a storm chaser for KFOR-TV's 4WARN Storm Team, with his SRV Dominator 2 as 4WARN Dominator 4.
In 2015, Timmer chased an EF2 tornado, with his mother, as part of a Mother's Day gift. In 2016, Timmer filmed a photogenic EF2 tornado near Wray, Colorado on May 7, that went viral, garnering nearly 43 million views as of May 2021. In November, Timmer joined AccuWeather, covering severe weather until 2019. A year later, on May 16, 2017, Timmer deployed a weather probe inside an EF2 tornado southwest of Elk City, Oklahoma, which recorded a 360-degree video that received praise from AccuWeather affiliates.
On January 23, 2018, Joel Taylor, one of Timmer's friends and the driver of the SRV Dominator vehicles, died from a drug overdose while on a cruise ship in San Juan, Puerto Rico. As a result, Timmer stated that he was "shocked and absolutely devastated by the loss of my incredible, caring friend", while also reporting his death. That same year, Timmer chased several natural disasters, including Hurricane Michael and a tornado in Federal, Wyoming, the latter event of which he recalled seeing "cows flying through the air".