Flash Flood and Hail in Arizona, August 31, 2015

Scattered strong thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, affecting downtown Phoenix. The storms generated gusty and damaging outflow winds estimated to be as high as 70 mph. According to a local broadcast media report, gusty winds blew down a billboard at the intersection of Grand Avenue and Encanto Boulevard, near the Arizona State Fairgrounds. At the same time, broadcast media also reported that trees were blown down across 7th Street at Roosevelt in downtown Phoenix.

Scattered thunderstorms developed across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and the stronger ones generated multiple reports of severe wind gusts, both estimated and measured, in excess of 60 mph. Some of the strongest gusts were reports in the area around Phoenix Sky Harbor Airport and Papago Park. At 1942MST the official ASOS weather sensor at Phoenix Sky Harbor Airport measured a gust to 61 mph. Soon afterwards, at 1955MST, a mesonet weather sensor 1 mile west of Papago Park measured a gust to 63 mph. At 2010MST another mesonet weather station 2 miles north of Papago Park measured a wind gust to 60 mph. Finally, just 5 minutes later local broadcast media reported an estimated wind gust to 65 mph at 74th Street and McDowell Road, about 2 miles northeast of Papago Park.

Strong thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st and in addition to strong gusty winds, some of the storms produced intense rainfall with peak rain rates well in excess of 1 inch per hour. The heavy rain led to episodes of urban flooding and flash flooding; one location that was hit hardest by flash flooding was downtown Phoenix. According to a local broadcast media report, at 2020MST intense rainfall flooded the deck park tunnel in downtown Phoenix, causing numerous drivers to become stranded in the tunnel. Shortly thereafter another driver became stranded due to flooding at the intersection of 48th Street and Van Buren Avenue. In addition to the flash flooding there was urban street flooding in the area. At 2004MST the public reported that water was 4 inches deep on Interstate 10 at 7th Street. A bit later, at 2031MST a public report indicated curb-to-curb street flooding at the intersection of 22nd Street and Osborn Road 4 miles north of Sky Harbor International Airport. Flash Flood Warnings were issued for the area beginning at 1945MST and continuing through 2315MST. Fortunately there were no reports of injuries due to the flooding.

Strong thunderstorms developed across portions of the greater Phoenix metropolitan area, including the community of Tempe, during the evening hours on August 31st. Due to a favorable combination of elevated moisture, instability, and wind fields aloft, the stronger storms produced gusty and damaging microburst winds which were estimated to reach as high as 75 mph at times. The microburst winds produced significant damage across the northern portion of Tempe. According to an article in the Arizona Republic, very strong winds ripped off part of the roof at the Integrity Charter School in Tempe. City spokeswoman Melissa Quillard reported that the Tempe Center for the Arts sustained roof damage and about one half of the trees around the center were damaged. Finally, it was reported that the pedestrian and bicycle bridge across Tempe Town Lake was significantly damaged by the microburst winds. Repairs to the bridge were estimated at one quarter of a million dollars; the bridge was closed and will remain closed until futher notice. No injuries were reported as a result of the damaging winds.

Scattered strong thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and they affected the community of Tempe. Some of the stronger storms produced gusty and damaging outflow winds in excess of 60 mph; the winds blew down numerous trees. According to a trained weather spotter 2 miles northwest of the Tempe Marketplace in north Tempe, damaging winds estimated to be as high as 70 mph blew down numerous large trees along Scottsdale Road south of east McKellips Road. At the same time, a report from the public indicated numerous large trees down near 68th Street and McKellips. Additionally, at 1950MST another public report indicated that strong winds downed a streetlight pole on College Avenue just north of Curry Road, near the Arizona State University campus.

Scattered thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st and due to a favorable combination of elevated moisture, instability and winds aloft, some of the stronger storms produced gusty and damaging microburst winds. One location that was especially impacted by the damaging winds was the Phoenix zoo in north Tempe. According to a report from local broadcast media, microburst winds estimated to be as high as 70 mph blew down numerous trees at the zoo and as a result, the zoo was closed for three days. Fortunately, there were no injuries reported as a result of the strong winds.

Scattered strong thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st; the stronger storms generated gusty damaging microburst winds estimated to be as high as 75 mph. Some of the most significant damage that occurred was just north of Papago Park. According to a trained weather spotter, strong microburst winds uprooted and blew down several large trees with trunk diameters ranging from one to three feet. Other large trees in the area had large branches snapped off. The damaged trees were located about 2 miles north of Papago Park. In addition, the winds caused damage to both roofs and brick walls of a nearby apartment complex. Penny sized hail was also observed. Fortunately, there were no injuries reported as a result of the strong microburst winds.

Scattered thunderstorms moved across Scottsdale during the evening hours on August 31st and some of the stronger ones generated gusty and damaging outflow winds. According to a report from local broadcast media, gusty winds estimated be as high as 60 mph downed power lines near the intersection of east Chaparral Road and Highway 101, about 2 miles northeast of downtown Scottsdale. The report did not mention if any power poles were downed as well.

Strong thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and in addition to gusty damaging winds, some of the stronger storms produced large hail. According to a trained spotter, penny sized hail was observed about 2 miles north of Papago Park in far southern Scottsdale. The hail fell near the intersection of 60th Street and Thomas Road.

Scattered strong thunderstorms developed across the central portion of the greater Phoenix area during the evening hours on August 31st, and some of them affected north Tempe, around Arizona State University. The storms produced gusty outflow winds in excess of 60 mph. A trained weather spotter 1 mile northwest of Arizona State University estimated that sustained winds reached 65 mph at the intersection of Roosevelt and First Street in Tempe. The spotter did not indicate that damage occurred due to the strong winds.

Scattered thunderstorms moved across the southeast portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and some of the stronger storms generated gusty and damaging outflow winds. Some of the winds damaged trees in the area around the Arizona State University campus in north Tempe. At 2030MT, a member of the public reported that gusty winds downed trees and blew shingles off of roofs near the intersection of Mill Avenue and Broadway Road in north Tempe. The winds were estimated to be in excess of 60 mph. About 30 minutes earlier, the public reported that gusty winds downed trees along University Avenue between Priest Drive and the Loop 202, about 2 miles west of the college campus.

The atmosphere over the greater Phoenix area was very moist and unstable on August 31st, and as a result, scattered thunderstorms developed during the evening hours; some of these storms affected downtown Phoenix. The stronger storms produced intense rainfall with peak rain rates in excess of 2 inches per hour. According to an article in the Arizona Republic, heavy evening thunderstorm rainfall caused significant damage to the Phoenix Veterans Medical Center near downtown Phoenix. Hospital spokeswoman Jean Schaefer said that torrential evening rains poured water into the west and south sides of Carl T. Hayden VA Medical Center's main building, causing damage in the intensive care unit, the emergency department, inpatient wards and other areas. At least 67 beds were out of service due to the rain damage. The water impact was described as pervasive, affecting most floors in the hospital and about 40 rooms. Schaefer said that a contractor will be tearing out sheet rock and inspecting for mold, asbestos, and other structural issues. The damage forced officials to move dozens of patients, reschedule some medical procedures and cease new-patient admissions. The closed areas of the hospital will not reopen until construction work is completed and inspections are passed.

Scattered thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and some of the stronger storms produced gusty and damaging outflow winds which produced damage in the vicinity of the Arizona State Fairgrounds. According to a broadcast media report, at 2016MST outflow winds estimated to be at least 65 mph downed a number of power poles near the intersection of 17th Avenue and Thomas Road. As the poles fell, power lines became draped across some of the houses in the area. The downed poles were located about 1 mile north of the fairgrounds. As reported in the Arizona Republic, the resulting power outage caused a significant loss of food at the St. Mary's Food Bank Alliance; between 50,000 and 60,000 pounds of dairy products stored at St. Mary's facility were lost. The facility was located near 31st Avenue and Thomas Road. According to Jerry Brown, director of public relations at St. Mary's, they are seeking donations to replenish the 100 thousand dollars in lost goods due to the soaring temperatures following the loss of power. Additionally, a trained weather spotter reported that strong winds blew down numerous trees at the intersection of 27th Avenue and Van Buren Street, about 2 miles southwest of the fairgrounds.

Thunderstorms moved across the northeast part of the greater Phoenix metropolitan area during the evening hours on August 31st and they affected the community of Paradise Valley. One of the storms produced gusty and damaging outflow winds. According to a report from the public, gusty winds estimated to be in excess of 60 mph blew down a tree about 3 miles northeast of Paradise Valley. The tree landed on a car at the intersection of Scottsdale Road and Shea Boulevard. The report did not indicate if any injuries occurred to the occupants of the car.

Scattered strong thunderstorms affected the southeast portion of the greater Phoenix metropolitan area during the evening hours on August 31st, including the town of Mesa. The stronger storms generated gusty outflow winds as high as 60 mph. According to an amateur radio report, at 2030MST a wind gust to 60 mph was estimated to have occurred in central Mesa, about 2 miles to the northeast of the Fiesta Mall. No damage was reported in the area.

Scattered thunderstorms moved across the southeastern portion of the greater Phoenix metropolitan area during the evening hours on August 31st; some of the stronger storms generated gusty and damaging outflow winds estimated to be as high as 70 mph. According to a trained weather spotter located just south of Dobson Ranch, or 3 miles south of the Fiesta Mall, strong winds uprooted a tree with a diameter of 8 inches. The winds also snapped a tree nearly 1 foot across and as the tree fell it brought down a nearby power pole. Metal siding was damaged on a temporary building in the area. The damage occurred near the intersection of Alma School Road and West Elliot Road.

Scattered thunderstorms moved across the central portion of the greater Phoenix metropolitan area during the evening hours on August 31st, and some of the stronger storms generated gusty and damaging outflow winds estimated to be in excess of 60 mph. At 2034MST local broadcast media reported that trees were blown down across 7th Street at East Roosevelt Street in central Phoenix. About 20 minutes later, a public report was received stating that strong winds blew down trees along 40th Street between Indian School Road and Thomas Road.