UPDATE 9 AM: The NWS report is now available. They pointed out that downsloping was a factor, and they got a look at the dust storm via images from their new dual-pol radar what?. In addition, one town got more rain in 9 minutes than 9 months with this system.
UPDATE 3 PM: The storms that were formed by this system turned into a rotating Mesoscale Convective Vortex (MCV) over southern California (see satellite photos below plus this one from AccuWeather.com). I'm not sure if the collision of the two outflow boundaries caused this, or just the strength of the first boundary and resulting storms. See high-res animation and still capture below. There is also another video of someone using a car-mounted camera to drive into the storm. The CIMSS blog has more information on the MCV and MODIS also captured this high-res image:
We have an excellent news story "Very Large and Historic Dust Storm' Sand Blasts Phoenix" detailing what happened last night in Arizona. This is the best video I've seen showing the approaching dust storm (or "haboob"):
The dust was tossed into the atmosphere over 20,000 feet into the air, as shown by the 3-D radar I pulled from GRAnalyst - in fact this is a rare case where what you see on the radar (hi-res | static | cross-section) looks exactly like what you see in reality, because it is picking up the dust as it overtakes the city. The dust storm was caused by a thunderstorm "outflow boundary" (see more below).*
The two-panel radar loop below (hi-res) is zoomed out, showing default radar (reflectivity) on the left and wind speeds (velocity) on the right. You can see the outflow boundary early on, moving northwest, then meeting another weaker boundary, moving southeast, and finally overtaking Phoenix.
One amateur weather station measured an 81 mph gust... which, although the sustained winds were low, I think is plausible...
Especially considering an official station (Davis-Monthan Air Force Base) topped out at 77:
The following photos are from AccuWeather.com Facebook fans.
The storm left a trail of wind damage and power outages as it moved from southeast to northwest:
*The way outflow boundaries are caused is illustrated thusly: Basically, cold air crashes down out of dying thunderstorms, hits the ground, spreads out, picking up dust on its periphery. As you probably noticed above, two outflow boundaries came together near Phoenix, but I'll await the NWS's report as to whether or not the two intercepting had something to do with the extreme winds. Sometimes when outflow boundaries interact, nothing happens; sometimes storms are formed (as shown SW of Phoenix in the radar loop), and sometimes they dissipate each other.
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