When a towering wall of dark clouds — thousands of feet high and miles wide — looms on the horizon, and moves quickly in your direction, it’s easy to fear the worst.
Watching a dust storm blow in, you can almost imagine it will leave a broad swath of nothingness in its wake, like the devastation you’d see in a science fiction story. Fortunately, it’s not like that at all.
Dust storm or haboob?
What’s the difference between a dust storm and a haboob — or are they the same thing?
A dust storm is formed when strong turbulent winds pick up loose particles of dirt and sand, creating a wall of wind that pushes across dry terrain. When there’s a wall of dust — like those seen above and below — a dust storm can be considered a haboob. (The word haboob is Arabic for “strong wind” — habb meaning “wind.”)
When a haboob-style dust storm is blowing in, from a distance, it looks like a solid wall of clouds close to the ground — very different to usual storm cloud formations.
Once you’re inside the wall of clouds, daylight instantly turns into a dusky evening light. All the dust that’s kicked up turns the air an orange-brown color, and the wind howls as it blows not just the sandy dust, but also leaves and litter and everything else that’s loose.
That’s one big haboob
The photo below was taken as one of the largest recorded dust storms rolled into the Phoenix metro area on July 5, 2011.
The National Weather Service termed it a “very large and historic dust storm,” and reported that, based on radar data, the storm is estimated to have reached a peak height of at least 5000 to 6000 feet, with the leading edge stretching for almost 100 miles — and the whole storm is said to have traveled at least 150 miles. (See another video clip of this haboob seen from a helicopter here.)
Where do dust storms come from?
What causes these huge dust storms? In the US — particularly the dry, desert areas of the southwest (including California, New Mexico, Arizona, Nevada, Utah and Texas — dust storms are most common in the summer time, often in the afternoon during monsoon season, when there is thunderstorm activity in the area.
Outside the United States, haboobs have been seen in the Sahara desert region, the Arabian Peninsula, Kuwait, Iraq, North Africa, Australia and Alberta, Canada.
USGS and partner research shows that two major contributing factors to the creation of these storms are low vegetation cover and disturbance to soil surfaces.
In the case of the Phoenix haboob mentioned above, the National Weather Service noted that there were several contributing factors to the storm’s intensity (all of which are common to dust storm activity — just not to the same degree as seen during this event).
Here are a few of the causes that worked in tandem to create this particular dust storm:
- Monsoon: In Arizona, dust storms most often occur during Monsoon season — which usually begins around the middle of June and lasts until about the second half of September.
- Dry land: There was an ongoing drought in the area between Tucson and Phoenix, where rainfall since the end of the last summer has been less than 50% of normal.
- Thunderstorms: In the afternoon, strong to severe thunderstorms developed east of Tucson. Thunderstorms in eastern and southern Arizona collided.
- Gaining strength: The storms intensified as they progressed west, producing downburst winds in excess of 70 MPH, raising and collecting dust.
- Force of gravity: Aided by gravity (as Tucson’s altitude is approximately 1500 feet higher than Phoenix) and additional downbursts from the parent storms, these strong outflow winds proceeded to race off to the northwest, with the leading edge moving at 30 to 40 MPH.
Dust in the wind
As freaky as the storms can look, haboobs and regular dust storms aren’t destructive like tornadoes and hurricanes. But as you’d imagine, driving is dangerous during a dust storm, because they can massively reduce visibility, and often occur with little warning.
If you’re driving when a dust storm hits, the Arizona Department of Transportation says to pull of the road and turn your lights off. Put on your emergency brake, and be sure you don’t have your foot on the brake pedal. Apparently, in reduced visibility, other people may see your car’s lights and attempt to follow — which is not a good move when you’re stopped. (For more specifics and tips, check az511.com.)
An issue that arises from dust storms and sand storms is the huge decrease in air quality due to the very small particles of dust, which are of concern because they can cause damage when they’re inhaled into the lungs. (Larger particles, on the other hand, get filtered out by your nose and throat.)
Finally, there’s the annoyance factor: dust storms of all sizes deposit a fine layer of dirt into swimming pools, on cars and on to everything else in its path.
Arizona dust storm: Amazing time-lapse of Phoenix ‘Haboob’
These time-lapse videos show a wall of dust moving through the city of Phoenix in Arizona.