Storm Expert

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Randy Cerveny, Professor of Geographical Sciences at ASU, talks about the huge storm system blowing across Arizona.

Ted Simons: We could see up to five inches of rain out of the latest storm to hit the state. Here to talk more about the apparent arrival of El Nino is Randy Cerveny, a professor of geographical sciences at Arizona State University. Thank you for being here.

Randy Cerveny: My pleasure.

Ted Simons: We should mention the county has declared a state of emergency and at the time of this taping, we're actually under a tornado watch. Is this the arrival the El Nino?

Randy Cerveny: This is definitely a strong winter storm and that's typical of a good El Nino year. We have rain that comes from here, stretching all the way back to L.A. It's still raining in Los Angeles right now.

Ted Simons: Let's describe what exactly El Nino is.

Randy Cerveny: El Nino is involving the water temperatures out in the Pacific Ocean. That normally the water temperatures out there are very cold. On a map that we have that shows temperatures, it would appear blue. When we monitor the temperatures during El Nino, which happens about once every five to seven years, the temperatures warm up so there's a giant red band --

Ted Simons: And we're seeing it right now. The warm water in the Pacific. Does that go away and the rain still comes? What's the timing of this now?

Randy Cerveny: There now. And it forces changes in where the storm track is. During most years, the storm track takes these winter storms and dumps them in Portland or Seattle. But during El Nino, they come down through southern California and into Arizona.

Ted Simons: Does this arrival of El Nino happen later than expected?

Randy Cerveny: Yeah, El Nino refers to Christmastime. Normally we see the first effects in and around December. It's been a pretty quiet December but looks like January will start with a bang and the forecast is that this is going to progress into March and April.

Ted Simons: I know we have another graphic that shows how much rain we're expecting. Looks like this is the start of something big.

Randy Cerveny: Right, the long-term prediction put out by the group called the climate prediction center, which is the group that makes long-term forecasts for the United States says there's an above normal chance for above-normal precipitation in the area from Southern California all the way to Arizona.

Ted Simons: And that's a whole lot of green in Arizona. Now, does this mean -- obviously, we talked last summer and you mentioned it looked like an El Nino kind of thing. Couldn't be sure then. With it here now, can we look at to next summer, next winter -- will there be a bigger monsoon?

Randy Cerveny: Not really. The El Nino circulation changes really impact more of the winter time precipitation which is more important to us anyway. The snow cover we get over the front range is what drives our water supply here. We can't tell whether this is going to mean a wet or dry monsoon this summer.

Ted Simons: When was the last time we had rainfall like this, a series of storms passing through to this extent?

Randy Cerveny: The last time in my memory would be back to '97. L.A. got 400% of their normal winter time precipitation. We ended up with 200% of ours. And if this is the forerunner, we're looking for another wet winter.

Ted Simons: When you say wet winter, can we expect storms of this magnitude of stopping by of systems?

Randy Cerveny: It depends on how long lasting this weather pattern is. This has got a lot of energy with it. In fact, the rain we're getting today will likely continue on all the way into Saturday and then we're going to get a little bit of a rest. And then on Tuesday, we've got another system coming through. The thing about an El Nino year, there's usually a lot of sequences of storms coming through.

Ted Simons: and it's because of the warming of the water in the Pacific moving the jet stream down. Now if we're getting all this business is Portland and Seattle bathing in sunshine?

Randy Cerveny: Actually that's the case. The northwest part of the United States is going to have dryer than normal conditions, a flip flop. If you get the wet area down here, it can't be up there, so they get dryer.

Ted Simons: How unusual for us to have a tornado watch in January?

Randy Cerveny: Well, this is actually the normal time we would have a tornado. Arizona, we don't get many and the ones we get are weak. We average one to two tornados a year and those one to two tornados usually occur in January with the result of the jet stream coming this far south. They tend to be really weak we tend to call them cold air funnels but this is the time we can have them.

Ted Simons: Thanks for joining us.

Randy Cerveny: My pleasure.

Randy Cerveny:Professor of Geographical Sciences, ASU;

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