Ted Simons: Good evening and welcome to "Horizon." I'm Ted Simons. It looked like something out of a Hollywood movie. A massive dust storm a mile high and 100 miles wide with winds in excess of 50 miles an hour hit the valley last night. Visibility in many areas was reduced to near zero as the wall of dust charged northward from storms between Phoenix and Tucson. Thousands of APS and SRP customers lost power during the storm and many more had to deal with a thick coating of dust on homes and cars. Even longtime valley residents were hard pressed to remember a dust storm of that magnitude. My goodness. Here now to talk about what causes these kinds of storms is Randy Cerveny, an Arizona State University president's professor in the school of geographical sciences and urban planning. Thanks for joining us.
Randy Cerveny: Thank you.
Ted Simons: How unusual was that storm last night?
Randy Cerveny: We haven't seen anything like that for a couple of decades. The amount of dust was reminiscent when the valley was much, much smaller and before we paved over and put houses and shopping centers in. The desert winds were able to come closer to the valley. Very much like last night. We hadn’t seen that because of the growth of the valley.
Ted Simons: A sign of the recession right there?
Randy Cerveny: Exactly. The weird thing is - given the recession and the fact that people have a lot of abandoned houses and lots and this type of thing, there was a dust supply available for those storms to come through.
Ted Simons: Wow, ok. How do dust storms start?
Randy Cerveny: Well, what you have to have is a mature thunderstorm. Down by Tucson last night there was a series of big thunderstorms that caused street flooding around oracle and Tucson. And as those storms die, their air comes crashing to the ground and spreads out as a bomb blast.so as it hits grounds, it picks up the dust.
Ted Simons:Is there a flashpoint for what we saw? At one point, was that just a little cloud of dust?
Randy Cerveny: Yeah, it was a small thunderstorm building up and producing rain over a given area and as it collapsed on itself and came crashing to the ground, it creates that wind.
Ted Simons: And it just keeps getting bigger and bigger, just like an avalanche?
Randy Cerveny: Right, as long as it has a supply of dust. And it still had the dust to maintain itself to Phoenix.
Ted Simons: Now, do you usually see these bigger dust storms earlier in the monsoon?
Randy Cerveny: Right because as the atmosphere gets moister, we'll see more rain, the first part of the monsoon season we call dry season, because it's the storms -- the rain kind of evaporates before it hits the ground and we're left with the wind. As we get later on in the month, we'll have more true thunderstorms with rain and lightning and hail than type of thing.
Ted Simons: Usually, it seems to me from what I remember, you got a dust storm and often a storm coming in after it. We didn't get that last night.
Randy Cerveny: Probably within the next few weeks, we'll have those storms with the rain behind it and then by the end of the month, just the rain.
Ted Simons: Interesting. Anywhere else in the country do we see these dust storms?
Randy Cerveny: You can have them occasionally in Texas and in the Great Plains during big droughts. In the 1930s, when we had the dust bowl days. Those were simply the same process. Storms that were dry having the air coming out and smashing into the ground and picking up the soil left over from the dust bowl days.
Ted Simons: And these are called Haboobs, because they're walls of dust. In the 19 30, they had the same Haboobs.
Randy Cerveny: They called them Black Blizzards, because the amount of soil they had in the Great Plains in Oklahoma and Kansas and Nebraska, dark in color and there was literally a black wall as opposed to the brown wall, the desert sands we had last night.
Ted Simons: Compare what we had last night to what happens in the Middle East.
Randy Cerveny: Very, very similar. The same kind of process is in place there. Those kind of storms are the same kind of heat generated, we call them convective thunderstorms that occurred here, last night. And as they die away, they put out the blast and our soldiers probably coming back from places like Iraq and Afghanistan felt at home because that was the same kind of storm they get there.
Ted Simons: How likely is it that you have a pretty -- let's say instead of a monster storm, a big storm? A big dust storm followed by a big dust storm. I know the monsoon seems to take off a night. Same with dust storms?
Randy Cerveny: Yeah, today we had a hazy day. A lot of dust suspended in the atmosphere. That tends to stabilize out the atmosphere. You don't get the strong surface heating you need to create a thunderstorm.
Ted Simons: The dust we saw today, that stuff is hanging around from last night?
Randy Cerveny: Exactly.
Ted Simons: Last question. You've been here for a while. You said in decades -- rank this thing. How impressive was this storm last night?
Randy Cerveny: I'd have to go back to the Glendale storm in '96 when all of the houses on the West side of the valley -- that was probably in terms of intensity, the last really big storm of this magnitude.
Ted Simons: And shouldn't see anything of that magnitude again or --
Randy Cerveny: Mother Nature likes to roll the dice. Occasionally it rolls snake eyes twice in a row.
Ted Simons: Good to have you on. Thanks for joining us.
Randy Cerveny: My pleasure.