On the night of December 26, 2015, a violent EF4 tornado struck the Dallas suburbs of Sunnyvale, Garland, and Rowlett, located in Texas. It caused $20–26 million (2015 USD) in damages, killed 10 people, making it the deadliest tornado in the United States in 2015, and injured 468 others. This was the third tornado to be rated an EF4 in the United States that year and the fourth such tornado worldwide.
The tornado first touched down at 6:46 p.m. CST and slowly began to intensify in strength while approaching Sunnyvale. As the tornado moved into Garland, it became violent, inflicting heavy damage on structures and vehicles. As the tornado crossed a highway, it struck a turnpike, where nine people who were sheltering in their vehicles were killed. Another man was killed when his house collapsed before the tornado lifted at 7:02 p.m., in Rockwall County. The tornado was the deadliest tornado ever to hit in the month of December in Texas, and one of the deadliest December tornadoes to hit the United States on record, alongside the 1953 Vicksburg, Mississippi tornado, the 1957 Gorham-Murphysboro, Illinois tornado, the 2000 Tuscaloosa tornado, the 2021 Western Kentucky tornado, and the 2015 Holly Springs-Ashland tornado that had occurred just three days before this event.
Prior to December 26th, 2015, the atmosphere was potent, with a strong upper-level trough throughout much of the Central and Southern Plains, accompanied by a large low-pressure area that crossed into the area from Mexico, resulting in a strong upper-level low that drew moisture from the Gulf of Mexico, with high dew points of 60 to 70 degrees. In the morning of December 26th, strong, low-level shear was recorded at 50 kts, as well as a looping 1 km hodograph that resulted in storm-relative helicity values upwards of 300 m2/s2. Additionally, MUCAPE values of 1793 J/kg created a capping inversion that somewhat limited tornado potential. By noon, the previous capping inversion had completely disappeared due to an increase in MUCAPE values to 2878 J/kg as a result of drastic increase in moisture from the gulf. In addition, hodographs continued to show a high probability for discrete supercells, and light cloud coverage in areas heated the ground in areas, further increasing instability.
The National Weather Service, who had noted a growing potential for severe weather as early as December 23rd, issued an enhanced risk for much of Northern Texas on the 23rd, with a 10% chance of tornadoes stretching from the Texas-Oklahoma border to portions of Central Texas. At 12:35 p.m., the NWS issued a tornado watch for Dallas County and the surrounding counties. By 1:43 p.m. supercells began to produce their first tornadoes, with the supercell that formed the Garland tornado forming by 4:50 p.m. The supercell would produce a few tornadoes, including one near the exurb of Waxahachie, before drastically increasing in intensity and becoming dominant around 6:40 p.m., producing the EF4 in Garland 6 minutes later.
The tornado first touched down on December 26, 2015, at 6:46 p.m. CST, on East Tripp Road north of US 80 west of Sunnyvale in Dallas County. The tornado produced minor roof damage to two homes in this area, and a power pole was knocked down near the tornado's initial touchdown point. The National Weather Service determined that the damage in this area was consistent with an EF0-strength tornado. Heading in a northeastward direction, the tornado began to slowly widen as it moved through mainly empty lots, although some EF0 damage occurred. After crossing Hearthstone Drive, the tornado rapidly strengthened to EF2 intensity. Several homes suffered severe roof and exterior wall damage, including some homes that were partially unroofed, vehicles were damaged, fences were knocked down, and trees were snapped. The tornado then weakened to EF1 intensity as it crossed Eagles Crest Drive, continuing to inflict roof damage to homes and damaging trees. The tornado then crossed Town East Boulevard and moved through unpopulated fields and wooded areas. There were few damage indicators in this area and an EF0 rating was given along this portion of the track.
After crossing Barnes Bridge Road, the tornado rapidly intensified to EF2 strength and struck the Plantation Place Dallas RV Park. Several RVs were severely damaged, including some that were flipped and others that were obliterated, including at least one destroyed RV that was thrown into a pond in the park. Vehicles were tossed and trees were damaged in the area as well. The tornado then entered the southeastern part of Garland and further intensified to EF3 strength briefly on Christina Lane. Several homes suffered extensive damage with roofs partially or completely removed and exterior walls damaged or knocked down. One unanchored home was swept off its foundation, while another saw more than half of the structure collapse. Vehicles were thrown and damaged, including a pickup truck that had its bed partially lifted off its axle and a box truck that was knocked over, a light pole was bent to the ground, and more trees and fences were damaged or knocked down. The tornado then weakened but remained strong as it continued northeastward at EF2 strength as it passed through residential areas. Many homes suffered severe roof and exterior wall damage, including some homes that were partially to completely unroofed and/or had exterior walls knocked down, and trees were damaged or snapped.
As the tornado crossed Bobtown Road, it rapidly intensified and became violent, moving through another residential area at EF4 intensity. Many homes in this area were heavily damaged or completely destroyed, including at least one home that was flattened on Crestpoint Lane. After crossing Kelso Lane, the tornado weakened slightly, but remained intense as it continued through residential areas at EF3 intensity. More homes were heavily damaged or destroyed with roofs removed and some to all exterior walls knocked down; some homes also had multiple interior walls knocked down. At least one home had a pickup truck thrown into it and some homes were partially swept away as well, although they were either unanchored or poorly anchored to their foundations, precluding a higher rating.The tornado then became violent again and reached EF4 intensity as it struck an apartment complex after crossing Locust Grove Road. Several single- or multi-story apartment buildings were heavily damaged or destroyed with upper and lower floor walls knocked down and roofs removed. One apartment building was completely flattened, a storage facility next to the complex was completely destroyed, and trees and power poles were snapped. All the apartment buildings left standing after the tornado struck were later condemned and torn down. The tornado then became deadly as it struck the I-30 and President George Bush Turnpike interchange. It tossed several vehicles and towed trailers off the elevated bridge ramps and into the traffic below. Nine people, including a one-year-old, were killed in this area. It also knocked down highway signs, bent and destroyed at least one large light pole that illuminated the interchange, and snapped trees. The tornado was rapidly weakening as it crossed through the interchange and it struck another RV park at EF1 intensity after crossing it, damaging trees and RVs in the area.
Beyond the RV park, the tornado continued northeastward and moved over Lake Ray Hubbard; because it struck no damage indicators on the lake, this segment was rated EF0. Upon coming ashore in the eastern part of Rowlett, the tornado reached EF3 intensity as it struck another neighborhood. Homes suffered extensive damage with roofs partially to completely removed and exterior walls knocked down. At least one home was completely flattened, at least one car was flipped, and trees were damaged or snapped. The tornado then continued northeastward through residential areas at EF2 intensity, continuing to partially to completely unroof and knock down the exterior walls of homes with others suffering moderate roof damage, and snapping trees and power poles. The tornado then regained EF3 intensity again on Channel Drive, where a home was mostly destroyed, a car was flipped, and more trees were snapped.