The synoptic pattern was characterized by strong westerly flow aloft situated across most of the Desert Southwest with embedded shortwave energy providing the main source for rising motion. 5 across most of central and southwestern AZ.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PSR wrote it up.
The synoptic pattern was characterized by strong westerly flow aloft situated across most of the Desert Southwest with embedded shortwave energy providing the main source for rising motion. Above normal moisture was present with PWATs in excess of 1.5 across most of central and southwestern AZ. The available moisture in combination with the daytime heating led to the development of moderate instability with MLCAPE in excess of 1000 J/KG. The strong westerly flow aloft led to strong vertical shear with 0-6 KM shear values ranging between 30-40 knots. All of these factors led to a very favorable environment for the development of strong to severe thunderstorms across portions of south-central AZ. Scattered thunderstorms started to develop by the early afternoon hours of the 12th with multiple rounds continuing into the evening hours. One severe thunderstorm in particular developed near the Buckeye area, became supercellular, and tracked generally eastward affecting areas such as Goodyear, Glendale, Phoenix, Scottsdale, Mesa and Apache Junction, causing extensive straight-line wind damage along its path. Additional thunderstorms developed just east of the Phoenix metro area during the overnight and early morning hours of the 13th, with the main impact being isolated flash flooding.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Phoenix, AZ wrote its last area forecast discussion before the first event at Sep 12, 11:16 AM MST, 2 hours 59 minutes earlier.
Area Forecast Discussion National Weather Service Phoenix AZ 1116 AM MST Tue Sep 12 2023 .UPDATE...18Z Aviation Discussion. && .SYNOPSIS... Temperatures will hover close to the seasonal normal the next several days as a series of weather disturbances pass through northern and central Arizona. Enough moisture will remain in place to support scattered showers and thunderstorms through the middle of the week with even some strong storms possible this afternoon. However, much drier air will surge back into the region during the latter half of the week cutting off any additional rainfall chances. && .DISCUSSION... Subtropical high pressure ridging has dropped further south into southern Sonora as strong westerly flow has become established across the SW Conus. A parade of shortwaves and small PV anomalies can be seen in early morning WV imagery embedded in a seasonably strong jet core directed towards the southern CA coast and local forecast area. These features combined with modest poleward moisture transport will result in multiple chances for showers and thunderstorms over the next 48 hours - primarily on the Arizona side of the CWA. Later in the week, a transitory omega-block type pattern will spread over the western Conus promoting pronounced drying and subsidence through at least early next week. A lead shortwave can be seen in both WV satellite and radar imagery crossing into SE California this morning while decaying convective complexes over Sonora were sending a series of outflows and gravity waves north. Modest chances still exist that isentropic upglide in the 310-315K layer combined with the intrusion of saturated midlevels (albeit in a lower lapse rate environment) could tap and release a large reservoir of elevated MUCape through southern Arizona this morning. So far, the only evidence of this evolution is occurring outside the forecast area, but it would not be a surprise if elevated convective elements begin materializing along the I-8 corridor later this morning. While likely incurring little immediate impact, the lasting effects in the form of enhanced, thick cloud cover on thunderstorm potential later in the afternoon may be more important. Late this afternoon, the environment may become more favorable for stronger convection as the kinematic parameters improve in the form of a 60-65 kt 200mb jet exit region and around 40kt 0-6km deep layer shear becoming established over the region. However as alluded to above, expansive thick cloud cover may compromise better surface insolation and more shallow mixing depths from a potential modified Gulf surge could compound the issue of substantial convective inhibition throughout much of the area. High resolution model output offers widely conflicting solutions yielding lower than normal forecast confidence. Based on recent trends, models have been subjectively been putting too much stock in thicker mid/high cloud influence; and feel similarly today, enough local breaks in cloud cover and a well mixed boundary layer (particularly over parts of SW Arizona) will foster MLCape 1000-1500 J/kg and deep convection. While overall ascent will be favorable, terrain features like the Kofas, Harquahala Mtns, and Harcuvar Mtns will be the most likely initiation points before updrafts migrate into lower elevations. Given the convective environment, a few organized storms or multicell clusters will be capable of developing with the greatest risks of strong to locally severe winds and localized severe hail (1" diameter). With deeper moisture profiles, DCape values may struggle to reach 1000 J/kg, however the vertical transport of higher momentum westerlies aloft may compensate for this deficiency. PWAT values around 1.75" and mean mixing ratios 11-12 g/kg would also support high rainfall rates (up to 1-2"/hr) which could result in localized flash flooding, however the stronger environmental shear and faster forward storm motion should preclude a more expansive flood threat. A fairly well defined, but weakening Pacific front should move into central AZ Wednesday as the final shortwave and upstream positively tilted trough ensures persistent westerly flow and a gradually subsident environment. However, sufficient residual boundary layer moisture should still linger around and east of the Phoenix metro with deep westerly flow aiding in orographic ascent. Several HREF members suggest another potential round of nocturnal/early morning elevated convective clusters Wednesday, however this evolution may be highly dependent on the outcome of thunderstorms this evening. Nevertheless, forecast BUFR soundings actually indicate a more favorable thermodynamic environment Wednesday afternoon with 10-11 g/kg mixing ratios juxtaposed with minimal inhibition and steeper lapse rates. Based on historical events, these situations typically result in scattered storms initiating over local terrain escarpments and foothills, but quickly moving into mountainous areas and exiting the CWA during the evening hours. Would not be surprised if future high resolution models start increasing storm potential and coverage during the day Wednesday east of the Phoenix metro. By Thursday morning, surface dewpoints in the 30s and mixing ratios below 5 g/kg may have already spread throughout the entire forecast area essentially cutting off rainfall chances. This dry regime should persist through the weekend as the pattern becomes temporarily blocked by a moderate amplitude quasi-omega feature, albeit still maintaining some form of westerly flow across the Southwest. Ensemble members show good agreement of H5 heights holding in a 586-590dm range and yielding a temperature forecast near to slightly above climatology. Even into early next week, the pattern of stronger than normal dry, westerly flow will be maintained sequestering monsoon thunderstorm activity well south into Mexico. && .AVIATION...Updated at 1755Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concern throughout the TAF period will be the potential for shower/thunderstorm activity late this afternoon through evening. Elevated southerly winds will be common heading into the afternoon. Strong to severe thunderstorms are expected to develop across south- central Arizona this evening as east to southeast winds take hold. The primary threats will be erratic winds, brief heavy rain, and lightning. There is a 30-50% for thunderstorm outflow winds to exceed 30 kts through the evening. Overall lower confidence in timing and direction of wind shifts through the period depending on how shower/thunderstorm activity plays out. Another round of showers and isolated thunderstorms may develop overnight or Wednesday morning. SCT-BKN clouds are expected mostly aob 8-10 kft. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation impacts are expected throughout the forecast period, besides gusty winds this afternoon through evening. Winds through the next 24 hours will favor a westerly component at KIPL with gusts upwards of 20-25 kts late this afternoon and evening. At KBLH, southerly winds will shift to the southwest and gust to around 20 kts this afternoon. Overnight, southerly winds will return with a period of variable winds possible at the end of the TAF package. Chances for showers and thunderstorms will be low (<10%) through the period. SCT-BKN clouds are expected aoa 10 kft before decreasing in coverage later today. && .FIRE WEATHER... With temperatures remaining near the seasonal normal, moisture will temporarily increase through the middle of the week aiding shower and thunderstorm chances. Eastern districts will have the greatest chance of wetting rainfall today and Wednesday. Minimum afternoon humidity levels will generally fall into a 20-35% range the next couple days, although drier air will quickly begin to infiltrate western districts. Overnight recovery should be fair to good in a 35- 70% range. Much drier air will sweep through the region during the latter half of the week with rainfall chances becoming neglible. Afternoon humidity levels should fall into the teens with less beneficial overnight recovery. Gusty afternoon west winds 20-30mph should be common the next several days with speeds relaxing later in the week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...Benedict/18 AVIATION...Leffel/Smith FIRE WEATHER...18
Special Weather Statement
National Weather Service Phoenix AZ
159 PM MST Tue Sep 12 2023
AZZ553-554-559-122145-
Sonoran Desert Natl Monument AZ-Northwest Pinal County AZ-
West Pinal County AZ-
159 PM MST Tue Sep 12 2023
...A strong thunderstorm will impact portions of Maricopa and Pinal
Counties through 245 PM MST...
At 159 PM MST, Doppler radar was tracking a strong thunderstorm 10
miles east of Freeman, or 23 miles west of Casa Grande, moving
northeast at 10 mph.
HAZARD...Winds in excess of 40 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Maricopa, Freeman, Stanfield, and Ak-Chin Village.
This includes the following highways...
AZ Interstate 8 between mile markers 142 and 172.
AZ Route 347 between mile markers 161 and 173.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3287 11232 3311 11198 3279 11175 3279 11187
3277 11189 3276 11205 3273 11205 3272 11214
3269 11216
TIME...MOT...LOC 2059Z 241DEG 7KT 3279 11213
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH
JLThe Phoenix radar (KIWA), 55 km away, was scanning. The volume nearest the first event began at 21:12 UTC.
22 thunderstorm wind, 4 hail, 3 flash flood. Local standard time, as filed.
Three downed power poles along West Miller Road about two miles west of Highway 347. Timing based on radar. Wind gusts were estimated at approximately 60 mph. No injuries were reported.
Downed power poles near the area Maricopa Rd and Highway 347 just west of I-10. Traffic signals were out leading to significant traffic impacts. Wind gusts were estimated at approximately 60 mph. No injuries were reported.
Public report of hailstones of 3/4 inch in diameter near Germann Rd and Dobson Rd.
Several large trees estimated to be up to 1 foot in diameter were uprooted in the area of West Indian School Road and North Litchfield Road in Goodyear. Wind gusts were estimated at approximately 60 mph. No injuries were reported.
Power lines were snapped in the area of North 17th Street and East Oak Street in Phoenix. Wind gusts were estimated at approximately 65-70 mph. No injuries were reported.
Giant 60 year old pine was uprooted, taking out two block walls as well as a couple power lines in the area of North 66th Street and East Oak Street in Scottsdale. Wind gusts were estimated at 65-70 mph. No injuries were reported.
A very large uprooted tree fell onto the roof of a home located along the area of North 40th Street and Indian School Road in Phoenix. Tree was estimated to be 90 feet tall with its root system at 13 feet in diameter. Winds were estimated at approximately 65-70 mph. No injuries were reported.
More than 100 trees downed in the city of Scottsdale parks, including 60 in the area of Vista Del Camino and El Dorado Parks. Wind gusts were estimated at approximately 65-70 mph. No injuries were reported.
A 60 foot pine tree was uprooted and toppled over a home causing damage to the patio roof. Wind gusts were estimated at between 65-70 mph. No injuries were reported.
Tree limb of approximately 6-8 inches in diameter was snapped from a large tree in the area of North Miller Road and East McDowell Road in Scottsdale. No injuries were reported.
Large tree uprooted in the area of Lindsay Road and East McKellips Road in Mesa. Wind gusts were estimated at 65-70 mph. No injuries were reported.
Multiple downed power poles and on top of houses in the area of Recker Road between East McDowell Road and East McKellips Road in Mesa. Multiple downed trees were also observed. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
Numerous reports of considerable damage at Falcon Field Airport from a severe microburst. Around 25 airplanes, mostly Cessna small aircraft, were damaged or destroyed, with some flipped over. One aviation flight school lost one third of their fleet, but it is unknown how many aircraft that amounts to. A few pilots reported that even planes with proper tie-downs broke free, with wind eyelets snapping and chains breaking as the planes likely tried to become airborne. Numerous hangars suffered significant damage, with around 90 hangar doors damaged or destroyed. Two World War II era hangars were damaged, with one losing its roof. Another hangar had an entire side wall shorn off. There were several downed trees around the airport, as well as damages to some other airport infrastructure and property, like fencing. A news report nearly three months later stated repairs are still being done and the total damages at the airport is around $7.2 million. An ASOS at Falcon Field Airport did not measure peak wind gusts from this storm due to a loss of power at the airport. Thus, based on damages, winds were estimated around 90 mph. No injuries were reported.
Home weather station located at 2915 East Minton Road in Mesa recorded a peak wind gust of 81 mph.
Multiple large trees were snapped and/or uprooted in the area of North Power and East McKellips Roads in Mesa. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
An AC unit was blown off the roof of a home located in the area of East Brown and North Power Roads in Mesa and landed on two brand new cars. The unit shattered the windshield of one car and dented the other car. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
Large tree approximately 9-11 inches in diameter was uprooted in 8534 East Halifax Circle in Mesa. Wind gusts were estimated at around 60 mph. No injuries were reported.
Severe damage occurred at Zaharis Elementary School located at the intersection of East McKellips Road and North Ellsworth Road in Mesa. Significant water damage occurred with several ceiling tiles ripped off as well as downed trees and debris across the campus. School was forced to close down for approximately a week due to the heavy damage. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
Downed power lines resulting the closure of North Cox Road between West Randolph Road and West McCartney Road in Casa Grande were reported. Wind gusts were estimated at approximately 55-60 mph. No injuries were reported.
Downed powerlines were reported in the area of North Pinal Avenue and West Val Vista Boulevard in Casa Grande. Wind gusts were estimated at approximately 55-60 mph. No injuries were reported.
A couple of mobile homes sustained severe roof damage in the area of East University Drive and Loop 202 in Mesa. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
Video showed hailstones up to one inch in diameter in the Mountain Bridge Neighbor in Mesa located just east of Loop 202. No damages or injuries were reported.
Video showed the roof from a home taken completely apart, flying approximately 100 feet away. Video also showed multiple large trees within the vicinity uprooted. The damage took place in a neighborhood complex located along North Recker Road just north of East McKellips Road in Mesa. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
Photo evidence showed damage to the roofing system as the satellite antenna dish of a home located at 2139 North Recker Road in Mesa. Hailstones were estimated to be up to one inch in diameter. No injuries were reported.
Large trees uprooted along with ceramic tiles on rooftops damaged in the Mountain Bridge Neighborhood located near East McKellips Road in Mesa. Wind gusts were estimated at approximately 80 mph. No injuries were reported.
State Route 88 between mileposts 229 and 242 southwest of Roosevelt Lake was closed due to flooding and rockslides, making the road impassable. No injuries were reported.
The overflowing from Weekes Wash lead to several road closures in Apache Junction including: Tomahawk Rd. (4th Ave to Junction St.); 4th Ave. (Tomahawk Rd. to Cactus Rd.); Junction St. (Tomahawk Rd. to Wickiup Rd.); and Scenic St. (Vista Rd. to Wickiup Rd.). No damages nor injuries were reported.
Nickel size hail reported in the area of East Thomas Road and Loop 101 in Scottsdale. No damages nor injuries reported.
Spring Creek Wash in Roosevelt was running about 3 feet deep. No damages nor injuries were reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2023Every state in 2023This day in weather historyWarnings in Arizona, September 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1139883, 1139884, 1141667, 1139885, 1139889, 1139892, 1140004, 1140005, 1140012, 1140013, 1140145, 1140006, 1140007, 1140010, 1140008, 1140009, 1140011, 1140014, 1140015, 1140016, 1140144, 1140146, 1140147, 1140148, 1140149, 1140017, 1140018, 1140019, 1140020.