Tuesday, July 24, 2012

Weekend Dust-Up in Phoenix

A haboob advances toward Yellow House Canyon near
the community of Ransom Canyon, Texas. June 18, 2009.
Credit: Wikimedia Commons
In the last post about monsoons one of the hazards listed was dust storms. Phoenix experienced a spectacular dust storm, or haboob, on Saturday, July 21. It was the first of the season for Phoenix.

Haboobs (Arabic for "strong wind") are common in arid parts of the world. In the U.S. haboobs occur in the Desert Southwest. They typically result from strong downburst thunderstorm winds. These winds spread outward from the storms, picking up loose, dry sand from the desert floor.  They often appear as a wall of dust hundreds of feet high advancing along the ground.

The haboob in Phoenix this weekend resulted from the outflows of thunderstorms that developed to the southeast of Phoenix and moved northwest.  The two radar images below show the outflow of the thunderstorms as they approached Phoenix, which likely marked the leading edge of the haboob.  It crossed through the Phoenix metro area from about 5:00 p.m. to near 7:00 p.m. local time. (Note that I was unable to find the time of the dust storm in news reports, but I did find it in the comments from our CoCoRaHS observers!)

This is the radar image from the NWS radar at Phoenix at 5;13 P.M. MST. The city of Phoenix is northwest of the radar. The white arrows point to the blue linear echo marking the outflow from the thunderstorms. The thunderstorms were moving from southeast to northwest.

This radar image shows the outflow boundary (marked by white arrows)
just about at the NWS radar site at 5:55 p.m. MST

The strong winds left almost 10,000 homes without power, and the dust reduced visibility to near zero in many areas. The dust was a nuisance and a health hazard, but it was also a boon to pool service companies and car washes in the area.

Here are some of the comments about the haboob from our CoCoRaHS observers, all from the observations on the morning of July 22. Suprisingly there were no Significant Weather Reports filed for this event!

AZ-MR-5    Sun City West 1.9 NNE    Apx 6pm Sat very strong winds with heavy blowing dust and poor visibility. Apx 8pm thunder/lightning/rain started. Apx 9:12pm VERY LOUD boom over our house with strong vibration and lightning. Heavy rain followed.

AZ-MR-25    Phoenix 4.2 NE    peak wind gust 47mph at 18:02:46 hours.

AZ-MR-68    Mesa 1.3 NNE    Haboob struck from ESE @ 1658 on 072112W? gusts < approx 50 mph. Rain began approx 1610, lasting about 20 min. (All blow and no show)

AZ-MR-72    Paradise Valley 2.8 NNW
    A lot of dust and wind last evening around 6pm. To call the rainfall "trace" is a gross overstatement. There was a lttle dust in the rain guage, probably associated with a few rain drops.

AZ-MR-157    Chandler 6.6 SE    dust storm, 50+ mph winds started about 6 pm with heavy rain and thunderstorm starting at 6:30 pm, lasted until 6:45 pm, 20 degree temp drop in 1/2 hour, rain and wind stopped with gradual clearing

AZ-MR-174    Surprise 5.1 NW    The blow came through about 6PM with lots of dust and high winds followed by loud and very close lighting and thunder around 8Pm and rain toaling 0.04 inches. Lost power little after 9PM for about an hour. This AM skys are clearing, winds very light from the North, humidity 63%, temp 84 degrees.

AZ-MR-287    Surprise 10.9 NE 
   1.28"... 2 miles NE of Happy Valley Rd./67th Ave close to Pyramid Peak. Was not home, but could tell from where we were near 107th Ave/Deer Valley that our home was being hit hard both by the haboob and later by the thunderstorm.

AZ-MR-57    Phoenix 7.4 NE
    partly cloudy. About 5:15 pm huge dust storm rolled in last night, totally obscuring the mountain from our location. Gusts of wind blew through the yard, whipping trees, then stilling. Later we would see lightning to the north, but we received no precipitation.

A freelance photographer for the Phoenix New Times took some spectacular photos of the haboob as it swept across Tempe and Scottsdale toward Phoenix. You can view these photos on the Phoenix New Times web site.

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