Was a sight to behold — one of the most incredible AccuWeather storm chasers Reed Timmer has ever had witnessed until that time in July 2018. A massive, mile-high wall of dust was hurtling toward afternoon commuters along Arizona’s Interstates 17 and 8 near Phoenix. The ominous burnt red curtain contained hurricane-force wind gusts, hail and torrential rain, drowning out rush-hour traffic with near-zero visibility as it headed west.
A haha what?
If you’re not from the Southwest (or live in a large desert like the Sahara or the Arabian Peninsula), chances are you’ve never heard the word. haboobs (pronounced hah tit) are particularly intense types of dust and/or sand storms that engulf areas for relatively short periods of time, typically 30 minutes or less.
“They’re caused by the small-scale but intense processes of thunderstorms and the resulting winds,” says Dave Houk, senior meteorologist at AccuWeather. Comparatively, “the more common ‘dust storm’ is generally driven by large-scale winds with strong low- and high-pressure systems and is less sudden and not as intense, but can have a longer duration.”
These huge dirty blogs are most likely to occur during the summer monsoon season in the southwestern US, as well as in North Africa and the Middle East. Places like Phoenix, Arizona, average several haboobs each year, but they’re much more common in Sudan, in the Sahara desert, Houk says.
Unlike many other meteorological terms with strict scientific definitions based on measurable characteristics, such as those that distinguish a tropical storm from a hurricane, with haboobs, there is no strict set of rules that lead to scientific classification.
However, Houk says: “However, there are characteristics that lead meteorologists to call it ‘haboob’.”
What makes a Haboob a Haboob?
You can usually see the sharp edge of a haboob’s wall of dust and sand in the distance. The accompanying and feeding ground-based winds typically gust to 30 to 60 miles per hour (48 to 96.5 kilometers per hour) or more. These massive clouds can extend vertically into the atmosphere for 10,000 feet (3,048 meters) and span up to a mile (1.6 kilometers). “But sometimes you organize thunderstorm lines that stretch more than 50 miles [80 kilometers] it can pick up sand and dust all along the line when conditions are right,” says Houk.
If you’re unlucky enough to get caught in one, he adds, “you can expect visibility to drop considerably, even close to zero, at ground level as the sand/dust cloud moves through the area.”
What causes a Haboob?
Haboobs are typically associated with the smaller-scale processes involved with strong up, down, and outward winds from a thunderstorm or shower, says Houk. “We like to say ‘what goes up must come down,’ and that’s true when it comes to rising air.” Rising air creates showers and thunderstorms that can move at speeds of up to 100 miles per hour (160 kilometers per hour).
“As the strong upward movement causes a thunderstorm, the rain that begins to fall from the thunderstorm begins to create areas of downward moving air,” he says. “That downdraft of cooler air that descends around the periphery of the core of the upward moving air in the thunderstorm can be enhanced as evaporative cooling and downward falling raindrops add extra velocity to the thunderstorms.” downward moving winds.
When those downdraft winds hit Earth’s surface, they have nowhere to go but outward in the horizontal plane, usually strongest ahead of the storm core in the direction the storm is moving, Houk says. “We call the leading edge of these propagating winds a ‘gust front’ or ‘outflow’ of the thunderstorm.”
A haboob forms when the downdraft of air reaches the ground and kicks up dust and sand. That dust gets caught in the turbulent winds associated with the main storm’s circulation and begins to move along with the gust front.
They are dangerous?
Haboobs can damage property and threaten lives, Houk says. Sudden onset and low visibility for ground and air traffic can cause accidents, slowdowns and stoppages. Wind gusts can cause power outages and downed trees. Windblown dust can scrub vehicles and homes and cause paint and surface damage.
Airborne dust and sand also create a respiratory hazard. And the lightning and heavy rains that accompany thunderstorms can carry the risk of injury, fire and flooding.
If you’re in the path of an oncoming haboob, the best thing to do is seek shelter indoors, says Houk. If you are driving, stop in the safest place you can find. “If caught outdoors, cover your face with a cloth or clothing to prevent particles from entering your lungs.”
You can also rest easy knowing that these dust storms are usually short-lived. “The haboob often outgrows the advancing and decaying storm that caused it,” says Houk, “and the sand/dust storm [often] It dissipates in 10 minutes.