La Nina: Dry Weather Ahead for San Diego
Tuesday, November 23, 2010
Climate researchers say there is a strong La Nina condition brewing over the Pacific, a condition which usually means a wet fall and dry winter and spring. We explore what a La Nina is and what it means for water resources and fire danger this summer.
Climate researchers say there is a strong and perhaps lengthy La Nina condition brewing over the Pacific, a condition which usually means a wet fall and dry winter and spring. We explore what a La Nina is, what it will mean for San Diego, and what it means for water resources and fire danger this summer.
Guest: Ed Joyce, KPBS Environmental Reporter
MAUREEN CAVANAUGH: I'm Maureen Cavanaugh and you're listening to These Days on KPBS. After our windy, cloudy, rainy weekend, it may be hard to believe that San Diego forecasters are expecting a dryer winter this year. But the experts say California's whether cycles are well documented, and we're about to enter a la Nina cycle. This one may stick around for a while. Joining us to explain what that means for San Diego is my guest, KPBS environment reporter be Ed Joyce. Good morning, ed.
ED JOYCE: Good morning, Maureen.
MAUREEN CAVANAUGH: First explain to us what a la Nina is.
ED JOYCE: Well, a la Nina is defined as cooler of the normal sea surface temperatures in the central and eastern tropical Pacific ocean, and that's what affects the global whether patterns and la Ninas happen every few years and they can last as long as a couple of years. And the difference between la Nina, and el Nino, they both refer to changes in the sea surface temperatures across the central and eastern tropical punish. But usually the sea surface readings of South America's west coast range in the 60s and '70s Fahrenheit, while they exceed 80 degrees in the warm pool and central and western Pacific. So this warm pool expands to cover the tropics during el Nino, but shrinks to the west during la Nina. So they call this the el Nino southern oscillation, which is the process that includes both el Nino and la Nina. And notes are needed for this.
MAUREEN CAVANAUGH: It is complicated. But it's a cycle, right? I mean it goes from one to the other. Now, how do cool ocean surface temperatures actually affect rainfall.
ED JOYCE: Well, la Nina often features dryer than normal conditions in the southwest and late summer true the following winter. Which is what you're setting up for right now. Dryer than normal conditions also happen in the central plains in the fall and the southeast in the winter and can the Pacific northwest as we're seeing now as well, is likely to be wetter than normal in the late fall and early winter with a well established la Nina, and I think we're seeing some signs of that, at least the climate scientists would say now with the now we're seeing in Seattle, and western -- now we've seen in Seattle the last couple of days and throughout western Washington, western Oregon even.
MAUREEN CAVANAUGH: You know, it's sort of counter intuitive though, because ask any San Diego an who's been around for any length of time, and it's really been kind of wet, you know, towards the end of the summer, and this fall. Our rainfall is one and a half inches above average for the season already. Do we really have to worry about a dry year?
ED JOYCE: Well, there's a couple of ways to look at this. One is that la Nina typically means a whether or an average or above average fall in terms of precipitation, which can come in the form of rain or snow. And then it can peter out, I mean, literally, we get this gang buster start, and we're would have average now, then we hit a lull in maybe December or January, then that part of the winter, December or January, nothing happens. However, we talked to San Diego County water authority, Kevin wine berg, and he said there's sometimes where a la Nina can bring that wet whether from the Pacific north with, and it can ease into northern California which can actually help our water supply.
NEW SPEAKER: The only difference with the la Nina, the whether set they get in the FSC northwest, moves south and they affect the Sierra, so you could have some more precipitation up in the Sierras, while it's very dry here in Southern California. Of.
MAUREEN CAVANAUGH: So it's rather difficult for us to tell, simply by looking at the day to day whether, what's happening in the weather, whether or not we are in one of these cycles or not, right.
ED JOYCE: That's true. Although most of the forecasts say we are in a la Nina condition right now. The question is, how strong will it be, and clause Walter, one of the Nora forecasters who works f from the university of Colorado, he said he expects this to be a strong la Nina, and they're also concerned about this as he is about fire danger in the future, but he's also concerned about, that this la Nina could set up to come back -- to be back next year as well. So he's thinking that it could more of an effect not this winter but the following winter.
MAUREEN CAVANAUGH: Did he tell you why he thinks this might be a particularly strong la Nina.
ED JOYCE: He crunches through a lot of data, they use satellites, drifting buoys, sea level analysis, they look at the computer models over time, they look at the cycles, and based on evaluating that, and a lot of other data, he's come up with this forecast that this is a strong La Nina, and he expects it to be a two-year La Nina.
MAUREEN CAVANAUGH: With all this modeling and all this stuff, does he look back in the past where we did have a strong La Nina condition, and what was the result of that.
ED JOYCE: Yes, he says there was a three-year La Nina, from 98 - 2001. And he's looked at the detail of what happens in those years, and he's looked at the details of what happened in that, are and this is gonna be a similar, he's not saying it's gonna be a three-year event, lees looking at a two-year event, but he actually thinks it's gonna be a big event, in the sense that it comes and goes, and you get a full sort of like a fall spring in eye sense, and then it goes away, and then can comes back again. He made the analogy of the film fatal attraction, when the character Glen Close comes back again and again. Just when you think she's done, she's back again.
MAUREEN CAVANAUGH: Okay. That'll stick in my mind. I am speak with KPBS environment reporter Ed Joyce, and we are talking about predictions for a La Nina cycle in San Diego, which mean ace dryer winterer ahead. So it's kind of a two edged sword though that we're dealing with, we're talking about rainfall this season, considering we have had a pretty wet fall so far. And it's been pretty moist also in northern California. So when we're looking at rainfall this -- when we're looking at water supply this season in California what are we looking at for 2011, just next year.
ED JOYCE: We're set up fairly good for 2011, and there's two reasons for that, one is conservation efforts thought the state, and currently in San Diego County, the conservation effort has been phenomenal. The water authority will attest to that certainly. . And also we had a an average or better than average rain year the previous year, so the reservoir supplies, the storage supplies are up, as you recall, we had a three-year drought period which ended essentially in 2010, you know, into O9, 2010, so we've built up some storage supplies, so this allocation of state water is based on supplies that we currently have. So the reservoirs are much better than they were, say, a year ago at this time.
MAUREEN CAVANAUGH: So every year, our water authority requests a certain amount of water from the metropolitan water district and so forth, and always those requests are kind of like, say, we can just give us five percent of what you requested, and so forth. What are they expecting us to quiet for our request this year?
ED JOYCE: Well the State Department of water resource from the state water project, said the initial allocation, it's always a conservative estimate, is 25 percent of requested amounts. Now, last year at this time, that number was five percent, which was the lowest in the history of the state water project that dates back to 1967. So they did say, so far it's been an above average year, they anticipate that that request would be 60 percent by next spring. All these numbers mean we're looking at a good water supply for 2011.
MAUREEN CAVANAUGH: Now, when they say it's going to be a dryer winter, do they actually have any kind of idea as to how much rainfall we might expect? Let's say -- winter starts, December 21st, onward, are we about to see a dramatic shift in our whether pattern to a more dry cycle.
ED JOYCE: Well, that's the forecast of the La Nina. Typically we have a wetter fall, and then it starts to dry out over the winter months. Now anything can change, it is weather. It's not an exact science in the sense that we don't ebb what may change. There are a lot of factors involved in in weather patterns and that can change as Ken wine berg said, some of that precipitation could ease down into the Sierra and just, you know, last weekend, mammoth had 81 inches in a weekend, this is phenomenal. And it does encourage water managers but they have been through this before where it starts fast and then dries out.
MAUREEN CAVANAUGH: Part of your piece this morning was kind of scary, because of what the consequence of what a dryer winterer, even if we don't feel it in our coming water supply this coming year, we may see increased fire danger. Tell us a little bit about that.
ED JOYCE: Well, you have this wet fall, so the water saturates the ground, a lot of vegetation springs up, let's say. We get a warming period, so we have a lot of dry fuels that are available to burn, and if we have an intense, you know, a really dry winter going into the spring, the fire danger could be very intense. Clause weighter from Noah and the university of Colorado spoke to that. Of.
NEW SPEAKER: I think we're starting out well, so my concern is less with next year, really in terms of the water supply. Then the year after. Southern California obviously when you have a dry winter, and you get into the spring season, we have had some very unusual fire seasons in the last five years. And this is the kind of set up you have to worry about, that you might get some early season fires rather than having the luxury of waiting, you know, until the fall season. So if we go through this winter on the dry side, I would say watch out in the spring for maybe some early season fires?
ED JOYCE: Again, if -- you know he qualifies that with if. So we have to wait and see. We're not sure. He's referring to those fires, the cedar fires in 2003, the '07 fires as well in San Diego County. Those were fall events predominantly. Spring is a lot sooner and a scarier possibility.
MAUREEN CAVANAUGH: It certainly is. Now, let me ask you, and I don't know if you can answer this question, ed, but I'm gonna ask it to you way, because I know your knowledge about weather and all of this, you've deputy a lot of research, has anybody explained last summer?
ED JOYCE: Funny that you should mention that. Actually dane canon from Scripps institution of oceanography, excuse me, referred to that recently. He didn't connect it to La Nina or El Serrito, it was just an unusual event in the pattern, the water temperatures being colder than normal in San Diego County. Certainly much the entire summer, and the weather was just a lot bit off, not typical. So it's part of a long range pattern perhaps.
MAUREEN CAVANAUGH: A long range pattern that perhaps we don't yet understand?
ED JOYCE: A blip. That, I can't say. They're always crunching through all that data and all the numbers, and computer models, but it stuck out. Now, a hundred years later, you look back, it might just be a small blip on that scale.
MAUREEN CAVANAUGH: Rather than something that starts and then the curve starts going up with the amount of cloudy days we had this summer?
ED JOYCE: Yes, and the way the climate change research shows, at least it indicates that what will happen in San Diego County, at least, it will get dryer, continue to be dryer, less rain, and there will be more rain and snow in northern California that will come sooner, but the Pacific northwest is supposed to have more intense winters, snow, rain, than they do now 678 and the last couple of years, last year and already this year, in the Pacific northwest, a lot of snow on the ground in the low lying areas, which is not typical. You usually get some no every, you know, 3, 4, 5 years in western Oregon, western Washington, and maybe there's a snow day or two, but nothing like a consistent -- it's went er, and then there's regular snow days.
MAUREEN CAVANAUGH: Bringing you back to San Diego, when La Nina really starts to kick in, if indeed these predictions are correct, and we see less rain, does it affect the temperature at all? Should we say colder days or does it have any effect on our actual day to day temperature during the winter time?
ED JOYCE: I don't know for a fact. But it seems that in other La Nina conditions, there's not a real radical change and all of a condition we're getting 40-degree temperatures, and the high for the day for example in San Diego is 50 degrees. I don't think there's a wide variation of the temperature, it's just more of an event related to precipitation, rain and snow amounts.
MAUREEN CAVANAUGH: Well, finally to try and end this on know upbeat note, one of the people you spoke with said at least we don't have to worry about flooding right.
ED JOYCE: Exactly, exactly, well less heavy rain events, with that sand bag event we had this weekend, they were making sand bags available. There's low lying areas, there's also flooding potential with not having those heavy rain it is potentially at least in the forecast right now, at least in the extreme events, that means no flooding.
MAUREEN CAVANAUGH: Well, I'll try to do my calculations on that pool of ocean water expanding and what degree it's at this moment.
ED JOYCE: You can check your own individual buoy for the water temperature near you.
MAUREEN CAVANAUGH: I do appreciate it, ed, thank you so much.
ED JOYCE: You're welcome.
MAUREEN CAVANAUGH: I've been speaking with KPBS environment reporter Ed Joyce, if you'd like to comment, you can go on line, KPBS.org/These Days. Coming up, an update on food assistance programs in San Diego. That's as These Days continues here on KPBS.