Three tornadoes touched down in Arizona during last week’s severe weather outbreak: one in Heber-Overgaard, one south of Prescott on Spruce Mountain, and a third confirmed on Oct. 29 on Wing Mountain, northwest of Flagstaff. All 3 were EF-1s.
The third tornado had winds reaching 110 mph, was 600 yards wide and traveled 2.3 miles in a mere 6 minutes, starting at 5:41 a.m. on Wednesday, Oct. 21.
Arizona doesn't get many tornadoes, so this was a big event. The last time there were three tornadoes on the same day was Nov. 29, 2019, in metro Phoenix, but they were all EF-0s.
This severe weather outbreak was more similar to Arizona’s largest event back in October 2010, when 11 tornadoes touched down between Coconino and Yavapai counties, including two EF-3s — some of the strongest tornadoes ever in the state.
Generally, Arizona tornadoes are minimal, and the ones that do strike usually do so over remote land or forested areas, so there are rarely injuries, fatalities or costly damage. There are about five on average annually. In the past decade, there have been 60 tornado reports, none of which were above an EF-1. That’s fewer than what some states — like Kansas, Oklahoma and Texas — get in one year.
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In the entire 21st century, there have been 126 reported tornadoes in Arizona, still less than what Texas sees in an average year.
Ken Moore, left, a homeowner, and his cousin, Mike Reynolds clean up storm damage in Overgaard on Oct. 22.
Details on all three tornadoes took some time because the National Weather Service in Flagstaff has been slammed. The Warning Coordination Meteorologist on-site, Megan Taylor, said severe weather events like this are all-hands-on-deck when there are still warnings to issue, and they were still doing so through Friday, Oct. 23. This delayed how quickly they were able to get out and do storm surveys, which produce the ratings.
The survey process is much longer than it might seem. The primary goal is to determine the wind speed for the EF rating, plus the path and the maximum width of the storm.
But they don’t use the radar or other devices to measure that. Surveyors look at damage from point to point, walking around and taking notice of every kind of damage they see along the way: broken trees, home damage, commercial damage, downed utility poles, and such. The degree of damage helps indicate how strong the wind was; for example, whether a tree just has branches down, the trunk itself was snapped, or the whole tree was uprooted.
All three tornadoes were higher-end EF-1s of 105 to 110 mph, signifying moderate damage: significant roof damage, windows broken, outer doors damaged or missing, greatly impacted mobile homes and uprooted trees.
An interesting caveat that Taylor shared was that trees falling on homes are not considered a damage indicator in the way you’d think.
“Really, the wind damage was to the tree. The tree fell on the home and caused a lot of damage, but to assess the strength of the winds, you really have to look at the damage to the tree (itself).”
This whole process, walking from point to point along the entire path of the tornado, can take six to eight hours. Then surveyors still have to make it back to the office and input all of the data into mapping and other software before publishing it.
