On August 11, 1999, Salt Lake City, Utah, witnessed a rare and devastating event—a powerful F2 tornado that left a lasting impact on the community. Lasting approximately 10 minutes, this tornado was a significant anomaly given Utah's typically dry climate and mountainous terrain, which usually see an average of only two tornadoes per year, with a strong tornado occurring once every seven years.
The tornado tragically resulted in one fatality and more than 80 injuries, with 15 to 20 of these being serious. The total damage was estimated at about $170 million. A significant number of structures and natural features were affected, including 300 buildings or houses, out of which 34 were rendered uninhabitable. Additionally, 500 trees were destroyed, and another 300 sustained significant damage. Major power outages plagued downtown Salt Lake City, Capitol area, and portions of the Avenues.
The tornado inflicted specific notable damages, including considerable losses to the Delta Center and Wyndham Hotel. Construction sites, such as the LDS Church's Assembly Hall, Memory Grove, and various residential areas, were also significantly impacted.
Given Utah's rarity of tornado occurrences, the event stood out even more. The atmospheric setup played a crucial role, as an upper-level trough of cold air moved into northern Utah from Nevada. This combined with warm southerly winds blowing over the Salt Lake Valley created ideal conditions for severe weather. Wind shearing and the jet stream contributed to the development of severe thunderstorms that acted as precursors to the tornado.
Localized breezes from the Great Salt Lake converged with southerly winds, further aiding in the storm's formation. This convergence zone was pivotal in transforming the severe thunderstorm into a tornado.
The tornado traveled approximately 3-3/4 miles with a width varying between 100 to 200 yards. At its peak, it reached F2 intensity, with wind speeds ranging from 113 to 157 mph. The tornado followed a northeasterly trajectory, originating around 400-500 South/Navajo (1340 West) and moving northeast through 300 South/1040 West. Key points of destruction included the Delta Center, Wyndham Hotel, and Memory Grove, and it eventually ended at Edge Hill/Terrace Hill (20th Avenue and P Street).
The trajectory of the tornado caused significant damage to notable landmarks. This included the Delta Center losing parts of its roof and many windows, and the Wyndham Hotel experiencing the destruction of almost every window.
Data indicate that 73% of Utah tornadoes occur from May to August, with 69% happening between noon and 5:00 PM MST. The 1999 Salt Lake City tornado struck early in the afternoon, fitting this common pattern for tornado events in the region.
There is likely an underreporting of tornadoes historically, but increased observations and public awareness have led to more accurate documentation. This differentiation is vital, as understanding the distinctions between tornadoes, dust devils, microbursts, and other phenomena is essential for accurate reporting and public awareness.
The broader synoptic events included the movement of the upper-level trough and warm southerly winds. The development began around Herriman and at the north end of the Great Salt Lake. The morning sounding indicated significant wind shearing, which was critical for the rapid intensification of the storm.
The storm rapidly intensified around 12:35 PM, and by 12:45 PM, the tornado had achieved F2 strength, causing widespread damage within 10 minutes.
Overall, the 1999 Salt Lake City tornado stands as a stark reminder of the power and unpredictability of severe weather, even in regions where such events are rare. The community's response and resilience blended with the increased awareness and detailed reporting ensures that the legacy of this tornado continues to inform and prepare Utah's residents for future events.
