Isolated thunderstorms developed and moved west across parts of southeast Arizona. One storm produced damaging winds that downed power poles near Santa Rosa.
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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 TWC wrote it up.
Isolated thunderstorms developed and moved west across parts of southeast Arizona. One storm produced damaging winds that downed power poles near Santa Rosa.
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 Tucson, AZ wrote its last area forecast discussion before the first event at Aug 27, 1:31 PM MST, 1 hour 59 minutes earlier.
Area Forecast Discussion National Weather Service Tucson AZ 131 PM MST Thu Aug 27 2020 .SYNOPSIS...Excessive heat will give way to cooler temperatures heading this weekend. Isolated showers and thunderstorms are expected through Friday, then an increase in thunderstorms is expected this weekend into early next week as additional moisture moves in. && .DISCUSSION...Showers and a few thunderstorms are developing right on schedule early this afternoon across portions of southeast Arizona. Latest GOES Total PWAT continues to show considerably drier air to the southeast of Tucson across much of Cochise County with PWAT values of 0.75"-1.00", compared to 1.00"-1.25" from Tucson westward. The bulk of the isolated thunderstorm coverage will be on a line from Bylas-Sierra Vista westward with the better chance of a few stronger storms mainly to the south to west of Tucson. A few thunderstorms are possible in the White Mountains as well. With the inverted-v sounding and DCAPE values of around 1500 J/KG, the main concern will be gusty winds and areas of blowing dust, especially to the west of Tucson. Some locally heavy rain is possible with the stronger storms as well. Storm movement will tend to be towards the west about 5 to 10 mph. Latest model runs shift the mid/upper level high to the east across NM on Friday placing southeast Arizona in a light southerly flow. Still enough moisture around as PWAT values average around or just above 1 inch to result in isolated showers and thunderstorms mainly from the Tucson area eastward and tending to be focused along and near the higher terrain. A gulf surge is expected to increase Friday night into Saturday in response to Tropical Storm Hernan off the southern tip of the Baja peninsula. As this occurs, the mid/upper high will shift southward into Chihuahua allowing a continued southerly steering flow. Saturday has the potential to be see a significant uptick in convection especially if we get considerable solar insolation with much deeper moisture and PWAT values around 1.25"-1.75". The increased moisture will continue through the weekend into early next week but as the high axis shifts south and elongates east-west, that will allow a more southwesterly flow aloft across southeast Arizona more reminiscent of a late monsoon transition pattern. Given the considerable moisture, there will still be plenty of opportunity for showers and thunderstorms Sunday and Monday as temperatures lower to below normal for late August given the deeper moisture. One thing to note with the deeper moisture is we may tend to lose some of the typical diurnal nature of thunderstorms. Looking further out into the middle of next week, most of the guidance is showing the mid/upper level high building to our north to northwest leading to a drier northerly flow. Still quite a bit of uncertainty in how this will all evolve and how much drier air will move in. Will go below some of the more aggressive NBM PoPs but still indicate isolated to scattered showers and thunderstorms through much of next week with temperatures near normal. && .AVIATION...Valid through 29/00Z. SCT-BKN clouds 10-15k ft MSL mainly in the afternoon and evening hours thru the forecast period. Isolated -TSRA possible this afternoon and evening as well as Friday. Favored areas are westward from far western Graham and Cochise Counties as well as the White Mountains. Expect the smoke haze to linger through the period. Aside from thunderstorm outflow gusts to 40 kts, surface winds generally remain less than 12 knots with afternoon/evening winds out of the northwest and variable at other times. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Through Friday only isolated thunderstorms are expected for most of the area with a bit more activity in the usual areas such as the White Mountains and vicinity of the International Border mainly west of Sierra Vista. This weekend into early next week moisture increases leading to a chance of showers and thunderstorms area wide. Temperatures will remain hotter than normal with minimum humidities 10-20 percent across the valleys and 20-30 percent in the mountains, with good overnight recoveries through Friday. Saturday into next week minimum humidities will generally be above 25 percent with normal to slightly below normal temperatures. 20-foot winds generally remain less than 15 mph outside of any thunderstorm gusts, which could reach 40+ mph. && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST this evening for AZZ501- 502-504>506-509. && Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Special Weather Statement National Weather Service Tucson AZ 209 PM MST Thu Aug 27 2020 AZZ502-272145- Tohono O'odham Nation including Sells- 209 PM MST Thu Aug 27 2020 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL PIMA COUNTY UNTIL 245 PM MST... At 209 PM MST, Doppler radar was tracking a strong thunderstorm near San Isidro, or 13 miles northeast of Sells. This storm was nearly stationary. Winds in excess of 40 mph and pea sized hail will be possible with this storm. Locations impacted include... San Isidro, Comobabi, Cababi, South Comobabi, Santa Rosa Ranch, San Luis - Sells District and Rincon. LAT...LON 3220 11170 3203 11161 3194 11188 3213 11198 TIME...MOT...LOC 2109Z 066DEG 3KT 3208 11175 AH
The Phoenix radar (KIWA), 118 km away, was scanning. The volume nearest the first event began at 22:30 UTC.
1 thunderstorm wind. Local standard time, as filed.
Thunderstorm winds downed nine power poles south of Santa Rosa. Power was out in several villages for two hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2020Every state in 2020This day in weather historyWarnings in Arizona, August 2020
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: 919565.