Golf ball-sized hail and destructive winds battered northern and central Arizona in an unusual storm that prompted seven tornado warnings, the first such alerts in the state since October 2010.
The National Weather Service issued numerous warnings as severe thunderstorms moved across the state overnight Tuesday into Wednesday, urging residents to take shelter and stay clear of windows as damaging two to three-inch (5-7.6-centimetre) hail struck the region. Hailstones hammered roofs, smashed windows and dented vehicles.
Unusual Storm Fuelled by Warm, Humid Air
Warm, humid air pushing north is fuelling storms rolling in off the California coast. Shifting winds can cause them to rotate, creating the conditions for tornadoes, explained Ryan Bernhart, a National Weather Service meteorologist in Flagstaff.
"This is very unusual for this area at this time of the year," Bernhart said.
Powerful winds brought down trees in Flagstaff and Mesa, with some crashing onto walls and carports. Several dozen ponderosa pines over 30 feet (9 metres) tall collapsed in the Coconino National Forest, northwest of Flagstaff.
Widespread Damage and Ongoing Threats
"These are not small trees that are down," Bernhart said. "These are pretty strong trees that had been knocked down."
The biggest danger to the Phoenix metro area is intense rainfall and flash flooding tonight and Thursday morning, said Mark O'Malley, a meteorologist at the National Weather Service office in Phoenix.
As a result, seven tornado warnings have been issued, with NWS representatives telling local media: "We typically issue a tornado warning somewhere in northern AZ just about every year, but today we’ve already issued seven, which is pretty rare."
