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Forecasters are saying there is a 65 percent chance of an El Nino weather pattern developing this winter, and that would mean a wetter winter than normal. Arizona State University climatologist Randy Cerveny will give us an update.

Ted Simons: Good evening and welcome to Arizona Horizon. I'm Ted Simons. It's that time of year when forecasters get a better idea of the chances that a wet el Niño weather pattern will hit in the coming winter months. ASU climatologist Randy Cerveny is here to tell us if we can expect an el Niño winter. Good to see you again.

Ted Simons: So, can we expect an el Niño winter?

Randy Cerveny: We can. The weather service is going up with a 70% chance that we will have this el Niño pattern, which for us, usually, means more rain.

Ted Simons: Ok. Define an el Niño winter weather pattern.

Randy Cerveny: Well, what happens with el Niño, it's a warming of the pacific ocean. Particularly, the area around the equator, and we've been seeing it start and start and stop for the last few months, but now, it's getting its act together. When it happens, that shifts the jet stream around, the storm track, so that the storms that would normally hit up in the Northwest, in Oregon and Washington, has come down into California and Arizona.

Ted Simons: And that's how it impacts Arizona. How often is Arizona hit by storms in an el Niño winter? Is it one of these few but heavy storms? Or lots of storms?

Randy Cerveny: Well, it depends on the strength of the el Niño. It's how hot is the Pacific Ocean? This one is not following a lot of the patterns, so we're still kind of throwing our hands up in the air. It looks like we'll get more than we normally would get which means we'll get five to six inches of precipitation across the state during next three months. But, any particular place, it's more difficult.

Ted Simons: When an el Niño hits, when does the rain usually start?

Randy Cerveny: Well, el Niño, actually, means the child, and refers to the Christ child, which tells us that the time that we start to see these things is around Christmas. That's when the pattern really starts to become apparent. With the storms that we have had and will see, it's on track to be this time of year that we'll have these.

Ted Simons: So what we had last weekend and the next couple days, that is part of el Niño?

Randy Cerveny: It is, indeed, and in fact, that kind of pattern does not seem to be changing. We'll have the small impulses, nothing really big but a lot of small impulses that will dump a good, moderate amount of rain over Arizona, better over California, and better up over the northern parts of Arizona.

Ted Simons: Now, a lower jet stream would suggest these are warmer storms, correct?

Randy Cerveny: Well, it has to do with where the moisture is coming from. You might have heard over the weekend, particularly in California, they were talking about something called a pineapple express. That's where the moisture is coming from the tropics, down around between 10 and 15 degrees latitude and gets pumped up into California, so it's warm rain. But, what happens afterwards is we get cold air that comes down from Alaska that follows behind that. That's why we get colds usually after one of these events.

Ted Simons: So an el Niño weather system could indicate lots of snow.

Randy Cerveny: It could, and in fact, this next storm is probably going to be a better snow producer than the one that we had over the weekend. There is more cold air behind it, so consequently, the snowbowl in Flagstaff should get more snow.

Ted Simons: The diversion for the pineapple express, why did they get hit so strong up and down California, and we got just nothing here?

Randy Cerveny: Well, it has to do with the orientation that, that moisture comes into California. You got the coastal mountains of California, and the moisture hits it and gets pushed up and dumped out. Very little of that is able to get over the mountains and make it all the way into Arizona. What does usually goes more to the north part of the state than the south part of the state. So, we miss out. What we need to have is the pineapple express move even further south so it crosses say Baja, as opposed to L.A.

Ted Simons: And much like the monsoon, if it comes up through Mexico we're going to get it?

Randy Cerveny: That's basically it.

Ted Simons: And that brings in another question regarding the drought. California is in a major drought, and we are in a drought. Is the drought that's affecting California, is it the same drought that's affecting us?

Randy Cerveny: Yes. And it has to do with the fact that over the last few years we have had the high pressure, the storms stay up in the Northwest, and we have had the high pressure over us, so that we have not had that rain. Not only has that high pressure sat over us but particularly over California, and Texas, and they have suffered worse things than we have.

Ted Simons: We are still in a drought?

Randy Cerveny: We are.

Ted Simons: Will the el Niño, it will help water supplies and all sorts of things, but how many -- like 75 el Niños in a row? Or what's going on?

Randy Cerveny: These are the storms that, if we continue to have a series of these, we like these, we get into the rim country, and that's what will get into the reservoir and is fill them up. So, it's these winter storms that are the drought busters.

Ted Simons: And I think that we have this chart that shows precipitation forecasts for Arizona. For the country. But, Arizona right there, that green, that's good, right?

Randy Cerveny: That is, indeed. This is a three-month forecast, December, January, February, and it's showing that there is above normal chances for precipitation, particularly, over the southwest. Everything from Texas to California, we have better than average chances of getting above normal precipitation.

Ted Simons: And that will last January, February, maybe into March, too?

Randy Cerveny: Possibly into March. El Niño usually starts to shift the pattern around March, so it's hard to go beyond that time. Everything is looking up like already we have seen the last few days. We'll have these storms coming through California.

Ted Simons: Before we let you go the impact of an el Niño, on Arizona, good for us, lots of rain. What about the Northwest, what about the east coast, what about the rest of the world?

Randy Cerveny: Well, it shifts the patterns around we'll see severe drought conditions over Australia, and unfortunately, it is the same way that we do, they get wildfires, so I would imagine over the next few months we'll hear of really bad wildfires that are going to take place in the Australia area. Some other parts of the world are, also, impacted. We have floods along Chile and Peru, and we have a tendency for a drought along the coast of Brazil. It's odd, it's pock marked places that are impacted differently. But, it's because the ocean, the Pacific Ocean controls so much of the world's weather that when you change it, you change that.

Ted Simons: Coast, more winter storms, anything?

Randy Cerveny: Probably -- if we end up with the storm track shifting to the south, they are probably going to have a bit warmer weather in the Great Plains, and a bit cooler weather right up in the New England states.

Ted Simons: All right, well, so you say el Niño has begun?

Randy Cerveny: That's what we're hoping for, and the weather service changed to 70% likely that we're going to have an el Niño winter.

Ted Simons: Good news. Randy, good to have you here and thanks for joining us.

Randy Cerveny: My pleasure.

Randy Cerveny:Climatologist, School of Geographical Sciences at Arizona State University;

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