Not even Dorothy or Toto noticed on Thursday evening in Phoenix, when a small tornado touched down in the metro area just after 5 p.m.
Surprisingly, the tornado was a minor inconvenience in the face of the destructive winds and flooding rainfall that slammed the downtown area in the monsoonal deluge. Several wet microbursts wrought havoc across the city, with the Phoenix Zoo suffering tree damage and an unwelcome cleanup headache Friday morning.
Over two dozen severe thunderstorm and flash flood warnings were issued Thursday, particularly over the East Valley. While this is somewhat typical for Phoenix in August given the seasonal pattern shifts and moisture streaming north, Thursday’s storms definitely brought their A-game.
The big story after the fact was a landspout tornado that apparently spun up near the downtown area. While no calls came in of tornado damage, at least two photographers snapped pictures as the quick-hitting vortex whirled up from the ground around 5:03 p.m. This is the first tornado to strike the Phoenix area since Oct. 6, 2015, when a twister hit near Goodyear.
However, this exceptionally weak tornado, dubbed a “landspout,” does not form from cloud-based rotation within supercell thunderstorms. Instead, landspouts develop in a way similar to their cousin, the waterspout; small vortices near the ground can be vertically stretched by storm updrafts, intensifying them just enough that they are able to cause damage.
While landspouts are still a force to be reckoned with, winds inside rarely exceed 65 mph, and they closely resemble large dust-devils. Thursday’s landspout didn’t even reach up to the cloud base.
“Weak tornadoes do occur in Arizona,” the National Weather Service in Phoenix told The Washington Post on Friday morning, “but they bear little resemblance to their Midwest counterparts. In reality, the wet microbursts created stronger winds and the flooding was far more dangerous than this brief, weak tornado.”
On rare occasions, Arizona does see much stronger tornadoes. Around noon on June 21, 1972, an F3 tornado carved out a one-mile path near the town Eloy, destroying several buildings and injuring 18 people.
Fortunately, Thursday’s tempest was comparatively calmer, but illustrates that all thunderstorms can be dangerous, tornado warning or not.
by Matthew Cappucci
August 4, 2017
