Arizona Dust Storm

A dust storm is a large wall of rapidly moving and blowing dust. It can create zero visibility in just one to two minutes, turn day to night, knock down trees and power lines, and leave a blanket of dirt and debris in its wake.

While a dust storm in Arizona can occur at any time of the year, this weather phenomenon is generally associated with the summer monsoon season, usually appearing between May and September.

Approaching a dust storm near the town of Eloy, AZ. Note the thunderstorm clouds in the distance which produced the storm

Dust storms are also officially known as haboobs, from the Arabic word habb which means "wind."

They usually form when a cluster of ordinary thunderstorms grow in light winds. The thunderstorm clouds begin to rise vertically, looking like huge towers of clouds in the sky.

These clouds then get loaded with water from the atmosphere, creating rain that falls to the ground and evaporates quickly, producing what meteorologists call "outflow."

The "outflow" or downdrafts hit the ground and are pushed out and forward in front of the storm, picking up dust and debris.

There can be just a few, or many, of these thunderstorms with outflow. If and when the outflows merge, it can cause widespread and often large dust storms.

Just such an Arizona dust storm occurred on July 5, 2011.

Although referred to as the Phoenix dust storm, the strong thunderstorms that caused it formed east of Tucson in the late afternoon.

As these storms intensified, they moved west into Tucson producing downburst winds over 70 MPH.

The historic Phoenix dust storm of July 5, 2011 approaching downtown Phoenix Courtesy of the National Weather Service - Phoenix

Tucson is 1,500 feet higher than Phoenix, so gravity and additional downbursts from the storms helped the strong outflow winds race towards the northwest.

Meteorologists estimate the leading edge of the dust storm was moving at 30 to 40 MPH.

By 7:00 pm, the leading edge of this historic and massive Arizona dust storm had hit parts of southeastern Phoenix.

The storm continued to push into metropolitan Phoenix over the next two hours with reports of near zero visibility and winds gusting from 30 to 50 MPH. There was even some wind gusts of almost 70 MPH recorded.

Observers reported that it reminded them of the Mt. St. Helens eruption with layers of dust coating every surface and the sky blackened by dirt and debris.

The storm also felled trees, brought down power lines, knocked out power, and caused flight delays and cancellations at Phoenix Sky Harbor Airport. It even blew over a semi-trailer truck on Interstate 8.

We took this photo while driving in a dust storm on Interstate 10 south of Phoenix

Based on radar data, the National Weather Service estimates that the July 5, 2011 Phoenix dust storm reached a peak height of at least 5,000 to 6,000 feet, with the leading edge stretching for almost 100 miles. The dust storm traveled at least 150 miles.

The dust finally began to settle by the time it reached Yuma, AZ later in the evening.

A blanket of haze upwards of 10,000 feet high still covered downtown Phoenix the following afternoon.

The ongoing drought in the area was also a factor in the size and intensity of the Phoenix dust storm.

The start of dust storms can be hard to forecast because it's hard for meteorologists to know when this type of merger will occur.

A typical dust storm in Arizona might reach 1,000 feet and travel between 30 and 40 MPH. On average, dust storms last about 10 to 30 minutes.

A warning sign over Interstate 10 between Phoenix & Tucson provides a dust storm warning to motorists

There are usually a few Arizona dust storms each year, frequently occuring along the Interstate 10 corridor between Phoenix and Tucson.

Though they are often over quickly, dust storms in Arizona are a definite driving hazard. They create blinding conditions and have been the cause of major vehicle collisions and pileups, so you should know what precautions to take when driving in dust storms.

Arizona Dust Storm Driving Tips

• If you are outside when an Arizona dust storm hits, get inside as soon as you can.
• Do not drive into a dust storm if you can avoid it.
• When entering a dust storm, be sure to turn on your headlights and slow down, traveling at a speed suited for limited visibility.
• Use the painted lane stripes to guide you.
• Never stop in the middle of the road.
• As visibility drops, it's advisable to find a safe place to pull off the road if you can. If you're stopping at the side of the road, try to get as far to the right as possible.
• Once pulled over, turn off your car engine and your headlights. Activate your emergency brake. Remove your foot from the brake pedal so drivers do not mistake your vehicle for one in motion.
• Wait out the storm until it passes and visibility returns.
• Be cautious when returning to the road way. Roads may be slippery, wet or cluttered with debris. Dust may be covering the pavement markings.

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