Dust Storm and Damaging Winds in Arizona, July 29, 2017

Name: Dust Storm and Damaging Winds in Arizona, July 29, 2017
Start: 2017-07-29T16:45
End: 2017-07-29T19:00
Location: Arizona

July 29, 2017 · NWS PSR · 9 events in 2 counties and zones

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $55,000
Crop damage: None recorded
Events: 9

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.

What happened

The episode as NWS PSR wrote it up.

Scattered monsoon thunderstorms developed across portions of the greater Phoenix metropolitan area during the evening hours on July 29th and these storms primarily generated strong gusty and damaging winds as opposed to heavy rain and flooding. A brief episode of dense blowing dust also occurred near the town of Maricopa, to the southeast of Phoenix. For the most part, peak wind gusts reached to around 60 mph and they were responsible for downing a number of trees in addition to snapping a light pole in El Mirage. However, one very strong gust was measured at 83 mph at Luke Air Force Base at 1656MST.

What forecasters said that day

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 Jul 29, 3:00 PM MST, 1 hour 45 minutes earlier.

Area forecast discussion, Jul 29, 3:00 PM MST, 1 hour 45 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
300 PM MST Sat Jul 29 2017

.SYNOPSIS...
High moisture levels have settled into much of southern Arizona
and will stay put at least through the weekend. This will bring an
increased chance of showers and thunderstorms, especially across
south-central Arizona. Subsequently, high temperatures decrease as
well...most noticeably over south-central Arizona. Next week will
remain unsettled each day with slight chances for showers and storms
over the deserts and higher chances across the higher terrain. High
temperatures will climb back to near seasonal normals.

&&

.DISCUSSION...
Active Monsoon day underway across the state, with broad coverage
of storms across the southeastern border as well as slightly lower
topped convection over portions of the Rim and northern Arizona.
AMDAR flight soundings in/around KPHX show one to two inversion
caps around 700 & above 500mb currently...possibly due to the
persist CU fields over the lower deserts throughout the morning.
Cooler daytime temperatures and capping inversions would
traditionally retard storm activity this evening, but additional
atmospheric support in the form of broad upper divergent fields
and various embedded MCV/IT circulations throughout the region
should work together to promote a bit more storm coverage this
evening than last. Current radar obs show activity already
intruding into northern Maricopa county along I-17 and near
Wickenburg. Hi-res models cluster a large area of rainfall across
portions of Phoenix by the evening, but realization of that
forecast solution would take some organized outflow intrusions and
intersections. With the moisture-laden airmass (dewpoints in the
60s and PWATs at or above moving regional averages for the date),
outflows may not have much dust or speed to them, but enough lift
to promote additional shower and storm activity across the region
into the evening.

The setup for this the rest of the weekend continues to be for
heavy rain with some potential for flash flooding given the
projected slow moving nature of the storms that develop. One
factor that will limit strength of convection this weekend is the
very cool high temperatures expected, especially over south
central AZ where highs Sunday will fall into the 90s. Of course,
the lack of typically intense summer heating will reduce
instability and potential strength of convection. POPs this
weekend remain high, in the 30-50 percent ballpark over much of
the area including central deserts.

For next week, Monday through Friday, we have a rather broad-
brushed, moderate grade monsoon forecast in place each day as
guidance is not clear cut on the small scale features that may
enhance convection. What does appear rather clear cut is that
moisture will remain in place area-wide through Friday, and there
will continue to be sufficient CAPE - especially over higher terrain
- to support typical afternoon and evening thunderstorm development.
Steering flow will stay on the light side each day initially
favoring a south to southeast flow and turning more to the northeast
by midweek, all the better to allow rim convection to drift down and
into the central deserts. Temperatures will climb a few degrees as
moisture backs off from the excessive levels seen this weekend, but
highs should stay near or slightly below seasonal normals for the
most part each day. Although moisture levels do back off slightly
during the week they do not drop enough to suggest a serious break
in monsoon convection.

&&

.AVIATION...

South-Central Arizona including KPHX, KIWA, and KSDL:

Thunderstorms will continue to build north/east/southeast of the
terminals. Today is expected to be a little bit more active than
yesterday. An outflow from the north is forecast to affect
terminals first (around 00Z) and then another outflow from the
southeast is forecast to affect terminals 2 to 3 hours later.
However, there is lower confidence on the exact timing and
direction of the outflow. Storms and showers in the vicinity of
the airport and even over the airport will be possible this
afternoon and through the overnight hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will follow their typical diurnal patterns for today with
just a few mid and high level clouds. Another chance of showers
moves in tonight for KBLH although confidence is much to low to
include any mention of precipitation at this point.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Monday through Friday: Thunderstorm activity will hang around
through Friday, with the greatest chances over the higher terrain
north and east of Phoenix. Minimum relative humidities will stay
above 20 percent across the board with great overnight recoveries.
High temperatures will be mostly below seasonal normals this
weekend, then gradually climb to near normal levels by Wednesday as
moisture and storm chances slightly decrease. Winds will otherwise
be light outside of any thunderstorm related winds.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

Visit us on Facebook, Twitter, and at weather.gov/phoenix

DISCUSSION...Nolte/CB
AVIATION...Hernandez
FIRE WEATHER...Hernandez

In the hours before

Special weather statement, Jul 29, 2:53 PM MST, 1 hour 52 minutes before

Special Weather Statement
National Weather Service Phoenix AZ
253 PM PDT SAT JUL 29 2017

CAZ560-292245-
Joshua Tree NP West CA-
253 PM PDT SAT JUL 29 2017

...SIGNIFICANT WEATHER ADVISORY FOR SAN BERNARDINO AND RIVERSIDE
COUNTIES UNTIL 345 PM PDT...

At 253 PM PDT, Doppler radar was tracking a strong thunderstorm near
Twentynine Palms. This storm was nearly stationary.

Winds in excess of 40 mph will be possible with this storm.

This storm will remain over mainly rural areas of San Bernardino and
Riverside Counties.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3408 11632 3408 11627 3412 11626 3412 11606
      3408 11604 3407 11600 3404 11601 3403 11599
      3400 11599 3398 11622 3402 11633
TIME...MOT...LOC 2153Z 221DEG 4KT 3409 11616

Iniguez

Special weather statement, Jul 29, 4:19 PM MST, 26 minutes before

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The radar

The Phoenix radar (KIWA), 74 km away, was scanning. The volume nearest the first event began at 23:43 UTC.

Open the radar archive at this moment

Event by event

7 thunderstorm wind, 1 heavy rain, 1 dust storm. Local standard time, as filed.

Thunderstorm Wind, Maricopa

When: July 29, 4:45 PM MST
Where: Maricopa County, 1.73 mi W of Ennis
Measured: 61 kt (70 mph) estimated gust
Property damage: $20,000
Reported by: Public
Coordinates: 33.630, -112.360

Strong thunderstorms developed across the western portion of the greater Phoenix area during the afternoon hours on July 29th and some of the stronger storms affected the community of Surprise. One of the storms produced strong outflow winds estimated to be as high as 70 mph. According to a report from the public, at 1645MST those strong winds blew over a trailer and a picture of the trailer was posted on social media. The trailer was located about 2 miles southwest of Surprise. No injuries were reported fortunately.

Heavy Rain, Maricopa

When: July 29, 4:48 PM MST to 6:45 PM MST
Where: Maricopa County, 1.5 mi NNE of White Tanks
Reported by: Public
Coordinates: 33.540, -112.420

Thunderstorms with locally heavy rain developed over the far western portions of the greater Phoenix area during the afternoon hours on July 29th, and some of the stronger storms affected the area around Luke Air Force Base. At 1725MST a Maricopa County flood control gage measured 0.71 inches within 30 minutes. The gage was located west of the base at the intersection of West Camelback Road and North Citrus Road. Heavy rain of this magnitude led resulted in urban flooding to the west of the air force base: at 1710MST a report from the public was received indicating that streets were flooded curb to curb and local basins and canals were above capacity. The flooding was just west of the loop 303, near West Glendale Avenue. An Urban and Small Stream Flood Advisory was issued for the area at 1648MST due to the heavy rain and it remained in effect through 1845MST.

Thunderstorm Wind, Maricopa

When: July 29, 4:56 PM MST
Where: Maricopa County, (Luf)luke Afb
Measured: 72 kt (83 mph) measured gust
Reported by: AWOS
Coordinates: 33.530, -112.380

Scattered thunderstorms affected portions of the greater Phoenix area during the evening hours on July 29th, bringing strong, gusty and damaging winds to communities such as Luke. At 1656MST, the official AWOS weather station at Luke Air Force Base measured a gust to 83 mph. This was the strongest wind gust measured in the Phoenix area on this day. A Severe Thunderstorm Warning was not issued for this storm, rather a Significant Weather Advisory instead.

Thunderstorm Wind, Maricopa

When: July 29, 5:00 PM MST
Where: Maricopa County, 0.9 mi SE of Webb
Measured: 72 kt (83 mph) measured gust
Property damage: $10,000
Reported by: Other Federal Agency
Coordinates: 33.540, -112.360

Thunderstorms with very strong winds developed across the western portion of the greater Phoenix metropolitan area during the late afternoon hours on July 29th and one particularly strong storm affected Luke Air Force Base. At about 1700MST the storm generated an outflow wind measured at 83 mph by the official AWOS weather station at the base. According to federal officials, the strong winds downed several trees and caused a variety of minor damage to the air force base. No injuries were reported however.

Thunderstorm Wind, Maricopa

When: July 29, 5:10 PM MST
Where: Maricopa County, 1.34 mi WNW of Youngtown
Measured: 52 kt (60 mph) estimated gust
Property damage: $5,000
Reported by: Broadcast Media
Coordinates: 33.590, -112.320

Scattered thunderstorms developed across the western portion of the greater Phoenix metropolitan area during the afternoon hours on July 29th and some of the stronger storms produced gusty and damaging outflow winds which affected communities such as El Mirage. According to local broadcast media, at 1710MST gusty winds estimated to be 60 mph knocked down a tree and snapped a light pole.

Thunderstorm Wind, Maricopa

When: July 29, 5:15 PM MST
Where: Maricopa County, 1.34 mi WSW of Ennis
Measured: 52 kt (60 mph) estimated gust
Property damage: $10,000
Reported by: Public
Coordinates: 33.620, -112.350

Strong thunderstorms developed across the western portion of the greater Phoenix area during the afternoon hours on July 29th and some of the stronger storms affected areas around the town of Surprise and El Mirage. The storms generated gusty and damaging outflow winds estimated to be as high as 60 mph. According to a report from the public which included pictures, strong winds downed a number of trees as well as power lines just to the southeast of Surprise. The damage was southeast of the intersection of Litchfield Road and West Greenway Road.

Thunderstorm Wind, Maricopa

When: July 29, 5:20 PM MST to 5:40 PM MST
Where: Maricopa County, 2.69 mi WNW of Litchfield Jct
Measured: 52 kt (60 mph) estimated gust
Property damage: $8,000
Reported by: Public
Coordinates: 33.450, -112.410

Scattered thunderstorms developed across the western portion of the greater Phoenix area during the late afternoon hours on July 29th and they affected communities such as Litchfield Park and Goodyear. The stronger storms produced gusty and damaging outflow winds estimated to be as high as 60 mph. At 1740MST a public report indicated that strong winds downed several trees and tree branches 3 miles to the southwest of Litchfield Park. About 10 minutes earlier, a trained spotter not far away, about 3 miles north of Goodyear, reported that strong winds blew down a tree with a diameter of 7 inches.

Thunderstorm Wind, Maricopa

When: July 29, 5:30 PM MST
Where: Maricopa County, 0.69 mi N of Tolleson
Measured: 61 kt (70 mph) estimated gust
Property damage: $2,000
Reported by: Emergency Manager
Coordinates: 33.460, -112.270

Thunderstorms developed across the western portion of the greater Phoenix area during the afternoon hours on July 29th and some of the stronger storms produced gusty and damaging outflow winds that impacted the community of Tolleson. At 1730MST, gusty winds estimated to be nearly 70 mph in strength snapped a palm tree in half, nearly three quarters of the way from the top of the tree. The snapped tree was reported by a local emergency manager and was located near the intersection of Interstate 10 and the loop 101 freeway, just north of the town of Tolleson.

Dust Storm, Central Deserts

When: July 29, 6:00 PM MST to 7:00 PM MST
Where: Central Deserts forecast zone
Reported by: Trained Spotter

Scattered thunderstorms developed across the greater Phoenix metropolitan area during the late afternoon hours on July 29th and some of the stronger storms generated gusty outflow winds that reached to around 50 mph. The winds were sufficiently strong as to stir up areas of dense blowing dust and create dust storm conditions; some of the especially dense dust affected the town of Maricopa located to the southeast of Phoenix. According to a trained weather spotter, at 1812MST a dust storm was present 4 miles to the northeast of Maricopa; dense blowing dust reduced visibility to 30 feet, creating very hazardous driving conditions. A Dust Storm Warning was issued at 1815MST as a result and remained in effect through 1900MST. Fortunately, no accidents or injuries resulted from the sharply reduced visibility.

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.
Dust Storm: Blowing dust that reduced visibility to a quarter mile or less.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Arizona in 2017 Every state in 2017 This day in weather history Warnings in Arizona, July 2017

Sources

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: 709874, 710132, 709861, 709862, 709886, 710130, 709867, 710131, 709863.