Arizona tornado warnings went out again and again on Wednesday, Oct. 21, as a storm system the National Weather Service called "very unusual" for this time of year moved across the state. It brought golf ball-sized hail, uprooted trees and a probable tornado in the mountain community of Heber-Overgaard. The state's first tornado watch since 2010 has now expired, but flooding and severe-storm risks continued into Thursday.
Key points
- Arizona's Family reported that the National Weather Service (NWS) issued at least 10 tornado warnings across Arizona on Wednesday.
- A tornado watch for Mohave, Coconino, Yavapai and Navajo counties was the first in Arizona since Oct. 6, 2010, according to the NWS (via KTAR). The NWS said it covered 675,516 people.
- NWS Flagstaff's radar indicated rotation over Heber-Overgaard at 7:02 p.m. MST. The Navajo County Sheriff's Office reported significant damage and minor injuries. As of Thursday morning, the tornado had not been officially confirmed.
- Hail 2 to 3 inches across shattered windows, damaged roofs and dented cars in northern and central Arizona, the Associated Press reported.
- Severe thunderstorm and flood watches remained in effect on Thursday, Oct. 22, including for the Phoenix area.
NASA satellite image of supercell thunderstorms over Arizona on Oct. 6, 2010, the last time the state was placed under a tornado watch before this week. Credit: NASA Worldview, public domain, via Wikimedia Commons.
How Arizona tornado warnings unfolded on Wednesday
The warnings began in the morning. KTAR reported that the NWS issued several for parts of Yavapai County around Prescott and parts of Coconino County in and around Flagstaff. All of them had expired by 1 p.m. with no confirmed sightings. Forecasters then issued a tornado watch for the northern half of the state until 6 p.m. It warned of possible tornadoes, hail up to the size of tennis balls and wind gusts up to 70 mph. The area under the watch contained 355 schools and 20 hospitals, the NWS said.
In the afternoon, NWS Flagstaff warned the Show Low area in Navajo and Apache counties after radar showed rotation in a storm moving northeast at 50 mph. At the same time, NWS Tucson issued a tornado warning for parts of Graham County, including Artesia. At 6:20 p.m., a storm capable of producing a tornado was located near Forest Lakes, 19 miles west of Heber-Overgaard, and was moving northeast.
That storm system is the one residents will remember. At 7:02 p.m. MST, NWS Flagstaff issued a tornado warning for a storm located directly over Heber-Overgaard and moving northeast at 40 mph. The warning cited radar-indicated rotation and hail the size of half dollars. Just 20 minutes later, the agency said the storm had weakened and was "no longer producing a tornado." NWS meteorologist Justin Johndrow told KTAR: "We believe that it did produce a tornado there." Official confirmation, however, requires a damage survey on the ground.
Damage in Heber-Overgaard, Flagstaff and the Valley
Heber-Overgaard is a Navajo County community of about 3,000 people, roughly 140 miles northeast of Phoenix. The Navajo County Sheriff's Office reported "significant damage and minor injuries" in Overgaard. A reception center for displaced residents opened at the Navajo County Heber Complex, and the American Red Cross is coordinating a shelter. State Rep. Walt Blackman requested a state-of-emergency declaration. "We have families without power, significant property damage, and at least one reported injury," he said, according to the AP.
Damage was also reported elsewhere. Strong winds brought down trees in Flagstaff and Mesa, and some fell onto walls and carports. In the Coconino National Forest northwest of Flagstaff, a few dozen ponderosa pines over 30 feet tall were knocked down. "These are not small trees that are down," NWS Flagstaff meteorologist Ryan Bernhart told the AP. He explained that warm, moist air moving north fuels storms coming off the California coast, and changing winds can make them spin. In the Phoenix area, Arizona's Family reported that a hailstorm tracked from the West Valley to New River and caused significant damage.
What's next on Thursday and the weekend
According to NWS alerts around 7:30 a.m. MST on Thursday, severe thunderstorm watches were in effect for Maricopa, Pinal and Gila counties until 11 a.m., for Graham and Greenlee counties until 11 a.m., and for parts of northern Arizona until 10 a.m. Flood watches ran as late as 11 p.m. in some areas, and a flash flood warning was in effect for part of Gila County. Arizona's Family said storms could bring gusts up to 70 mph, hail up to 2 inches and a brief tornado. It also noted that the Storm Prediction Center showed a 5% tornado chance in eastern Arizona around Show Low and Safford. As of 7:30 a.m., more than 200 flights were delayed at Phoenix Sky Harbor. Forecasters expect drier, cooler weather on Friday and through the weekend. Conditions can change quickly, so check the latest alerts from NWS Phoenix, Tucson and Flagstaff.
How to stay safe
- Tornado warning: Go to a basement, safe room or interior room on the lowest floor, away from windows. Mobile homes, sheds and tents are not safe. If you are in a vehicle, drive to the nearest sturdy shelter if you can (NWS).
- Watch vs. warning: A watch means conditions favor tornadoes. A warning means one has been sighted or indicated by radar, so act right away.
- Flooding: Never drive or walk into flood water. According to the NWS and Ready.gov, 6 inches of moving water can knock an adult down, and about 12 inches can carry away most cars. Turn Around, Don't Drown.
Why it matters
According to the Arizona State Climate Office, Arizona averages only four to six tornadoes a year, usually rated EF0 to EF2. Before this week, the state had not been under a tornado watch for 16 years. Many Arizonans may never have heard Arizona tornado warnings before, and many homes have no basement. Knowing the difference between a watch and a warning, and having a plan before storms arrive, can save lives. The final rating and path of the Heber-Overgaard storm will depend on the NWS damage survey, and WorldScope will update this story when results are published.
Sources
- NBC News / AP: Hail the size of golf balls pummels parts of Arizona
- The Guardian / AP: Arizona storms topple trees and bring golf ball-sized hail
- Arizona's Family: Severe weather, flooding threat continues across Arizona
- KTAR News: Significant damage, minor injuries reported in Overgaard
- KTAR News: Probable tornado hits Heber-Overgaard
- National Weather Service: Active alerts for Arizona (NWS Flagstaff, NWS Phoenix, NWS Tucson, Storm Prediction Center)
- NWS: What to do during a tornado
- NWS: Turn Around Don't Drown and Ready.gov: Floods
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