Tag archive for La Nina

SoCal 2014 water year forecast: Dryness, but…

For California, the Department of Water Resources releases an "experimental" long-term forecast, based on ocean indices. Lead forecaster Dr. Klaus Wolter of NOAA predicts — as he did last year — dryness, but opens the door to the possibility of an El Nino developing in spring.

The forecast's three central predictions for the 2014 water year:

► Mostly dry conditions for most of California, with dry conditions being especially likely in Southern
► Near-normal to drier than normal for the Colorado River Basin, an important source of water supply for Southern California, although not as dry as in water year 2013.
►A small chance of a spring shift to El Niño conditions that could bring wetter weather for Southern
California late in the season.

However, a look at a suite of projections appears a bit more promising for El Nino:


The forecasters write:

Most of the set of dynamical and statistical model predictions issued during late October and early November 2013 predict neutral ENSO conditions through the rest of 2013 and into early 2014, with a warming tendency during northern spring and summer 2014. Development of weak El Nino conditions appears possible by the middle of 2014. In the most recent week, the SST anomaly in the Nino3.4 region was 0.0C. Based on the multi-model mean predictions, and the expected skill of the models by start time and lead time, the probabilities (X100) for La Nina, neutral and El Nino conditions (using -0.5C and 0.5C thresholds) over the coming 9 seasons are:

Season La Ni�a Neutral El Ni�o
NDJ 2014 1% 99% ~0%
DJF 2014 3% 96% 1%
JFM 2014 4% 92% 4%
FMA 2014 5% 84% 11%
MAM 2014 5% 74% 21%
AMJ 2014 7% 59% 34%
MJJ 2014 10% 48% 42%
JJA 2014 8% 44% 48%
JAS 2014 9% 43% 48%

Another way to look at it might be — we have a substantially better chance of El Nino (which tends to mean a warmer, wetter spell) than a La Nina (which tends to mean a drier, colder conditions). 

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President Obama talks climate: 12 hottest years, in last 15

The earth’s getting warmer: “Yes, it’s true that no
single event makes a trend. But the fact is, the 12 hottest years on
record have all come in the last 15.” President Obama, in the State of the Union Address:

You can see that in NOAA’s record of global temperatures.

From Ezra Klein's Wonkblog. Weather nerds will note how much colder La Niña years once were, compared to neutral or El Niño years — but not today. 

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No El Nino or La Nina this year, just La Nada

Like the headline the Star put on my story from Saturday: No El Nino or La Nina this year, just La Nada

The crucial quote couple of graphs from the story, featuring media star and friend Bill Patzert:

Veteran forecaster Bill Patzert, who works with the NASA-affiliated
Jet Propulsion Laboratory in Pasadena on long-range forecasts for
Southern California, calls this condition "La Nada," because he thinks
the word "neutral" misleadingly implies that rainfall will be moderate
or "normal."

"You never want to say the word 'normal' when it comes to rain in
Southern California, because in the last 100 years, we've only had a
total of six 'normal' years of rainfall, meaning about 15 inches of rain
in a winter in downtown L.A," he said. "We have had one of the wettest
winters on record during a La Nada period, and one of the driest."

Here's a graph of the Pacific Decadal Oscillation, or PDO, which many climatologists believe governs rainfall in SoCal more than El Nino/La Nina/ENSO:
The graph is a few years old (2003). Patzert noted that during that freakish two weeks of rain in December 2010, it was positive, but as of late, has turned steadily negative. 

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What is going on with the alleged El Nino of 2012?

Six months ago, temperatures in the equatorial Pacific suggested that, after two years under the influence of La Niña, which tends to mean cold dry winters here in Southern California, that our ocean was turning towards an El Niño condition. Under that condition, warm temperatures and westerlies in the equatorial Pacific predispose those of us in California for wetter winters. This is what usually happens, after a long stay in one condition, that we transition to its counterpart. 

But now it appears that, unusually, the predicted El Nino is "petering out," in the words of Kevin Trenberth, a leading climatologist. Even more curiously, the statistical and dynamicla models are in disagreement, as discussed by Robert Henson of the National Center for Atmospheric Research. Henson highlights a curious fact about this year's discussion of the controversial boy El Nino

  • In March, the dynamical and statistical models tracked by IRI agreed that neutral conditions were most likely to prevail by late 2012.
  • By May, about half of the models called for a weak El Niño, while half still called for neutral conditions.
  • And by July, more than 70% of the models were calling for an El Niño. However, a clear split was now evident. Most of the dynamical models were calling for El Niño to appear, perhaps even a moderate to strong one, while the statistical models leaned toward neutral conditions or a very weak El Niño.

The statistical method, used to establish a probabilistic baseline, is about as skilled as the dynamical model as a forecaster. But the IRC [International Research Institute for Climate and Society] points out that the statistical method, which looks at the past record, might not pick up changes — perhaps including those brought on by global warming? — that the dynamical model can. The dynamical model plugs ocean temps and other values into a climate/ocean model and runs a projection. 

Here's an image of the rise and fall of ocean temps in the mid-Pacific this year, from Henson's excellent discussion


As you can see, the fall-off in temps has been rapid. What is going on? Could this be part of a broader trend towards drought, as discussed in this paper in Nature by Aiguo Dai? (h/t: Dot Earth

Have an assignment: Will try to find out, report back. 

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Possible good news: El Niño conditions developing

For those of us who are suffering through seemingly endless heat and dryness, to hear of a possible change in the forecast is comforting, and yes, the National Weather Service's Climate Prediction Center does see increased chances for an El Niño this fall. 

Supported by model forecasts and the continued warmth across the Pacific Ocean, there is increased confidence for a weak-to-moderate El Niño during the Northern Hemisphere fall and winter 2012-13. El Niño conditions are likely to develop during August or September 2012 (see CPC/IRI consensus forecast).


Also reassuring — the forecast sees little chance of another La Niña.

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Could global warming give us late, light flu seasons?

In Ventura, the Star's first-rate health and society reporter Tom Kisken documents the lightest flu season in decades. Seriously, for some reason, it's been 29 years since the flu season took until February to get started. Usually it happens by Christmas. That's according to the official Centers for Disease Control.

Why so late?

In California and Ventura County, officials also declared influenza a late bloomer that began to emerge in late January and early February. Activity remains mostly light.

Ask why and they say the same things as the feds: No way to know.

Over at The New York Times, Charles Pierce has an idea

Scientists are still studying the complex relationship between flu and climate, and other factors, like an absence of new strains or immunity from past vaccinations, may have contributed to this season's low numbers. But there is reason to believe that the weather is an important factor. For one thing, studies have extablished that the flu virus thrives in low humidity, and therefore low temperature — there's a reason, after all, that the flu usually hits us in January, not July. Cold weather also dries out the nasal passages, making it easier to get the coughts and sneezes that transmit the flu. And it keeps us cooped up inside, passing illnesses around. 

Ironically, the same La Niña pattern that may have suppressed flu transmission this year in the U.S. among humans could in the Pacific among birds lead to the creation of new and potentially dangerous viruses, according to a study presented in December at the AGU.

"We know that pandemics arise from dramatic changes in the influenza genome. Our hypothesis is that La Niña sets the stage for these changes by reshuffling the mixing patterns of migratory birds, which are a major reservoir for influenza," says Jeffrey Shaman, PhD, Mailman School assistant professor of Environmental Health Sciences and co-author of the study.

The climate giveth, and the climate taketh away. 

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La Niña misses SoCal, hits Sun Belt

As we've been discussing over the last few months, this past year's La Niña has been a bust in Southern California. What was expected to be a dry winter with winds and heat turned out to be a wet, blustery winter with massive Sierran snowpack. 

But not so across the U.S! As the NY Times reported yesterday, across the rest of the Southwest and deep into the Sunbelt and the South, this has been a classic La Niña episode, a huge drought that experts are now comparing to the Dust Bowl. 


[Click to enlarge]


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La Niña dry winter prediction fails in 2010, experts agree

This fall experts, including the Forest Service, were predicting a strong La Niña condition likely to produce a dry winter, with heat and Santa Ana winds.

The oceanic pattern developed, but the prediction? 

Bzzzttt! Wrong. Here in Ventura County, we're at roughtly 150% of normal, and got pounded by about six inches of rain over the weekend, stranding literally dozens of hikers, including both a Sierra Club outing and a Boy Scouts outing, in the backcountry, requiring rescue. More rain is expected this week.

Leader of the forecasting pack Bill Patzert admits: the predictions were a bust

I have a rain gauge, but my old wheelbarrow makes the point more impressively…


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Thin ice in the Arctic means cold winters back East?

Put perhaps as simply as possible, that's the speculation among some experts about the cold snowy winters experienced this year in many Northern hemisphere climates, such as New York.

Here's the most concise, detailed explanation I've found so far, from Climate Central:

Recent scientific studies have shown that the dramatic warming that has been occurring in the Arctic during the past few decades, along with the associated loss of sea ice cover, may be changing atmospheric circulation patterns throughout the northern hemisphere. This could be contributing to the recent outbreaks of unusually cold and snowy weather. Sea ice loss during the spring and summer melt season, which leaves a thinner and more sparse ice cover throughout the fall and early winter, is a key suspect in influencing winter weather patterns. When the ice melts, it allows incoming solar radiation to warm water and air temperatures, which in turn has an influence on atmospheric pressure and circulation, and may help shift Arctic air southward, while the Arctic remains unusually warm.

One meteorologist has described the pattern this way: "This pattern is kind of like leaving the refrigerator door ajar — the refrigerator warm up, but all the cold air spills out into the house."

It's important not to overlook the ancient planetary cycles, of course. Down here in SoCal, it feels the past few days as if La Niña has taken hold. It's cold and dry, with no sign of precip in sight. 


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What the heck is going on with this La Niña?

Isn't it supposed to be cold and dry in SoCal during a La Niña, not wet and warm?

Craig Miller of KQED asks questions, and gets answers from the helpful Kevin Trenberth of NCAR:

"In La Niña conditions, which is what we have now, the main storms that come into North America come barreling into Washington, Oregon and British Columbia more," Trenberth told [Miller] in a phone interview.

But lately a persistent region of high pressure in the north Pacific is diverting storms south, into California. Trenberth says: "There’s a crapshoot or a random component to it, if you like, in the more northern latitudes, that’s adding some extra flavor to what’s going on, I think."

Speaking of crapshoots, in a recent interview Bill Patzert pointed out that in eighteen of the last twenty-two La Niñas, SoCal did experience drier, colder winters than normal. And Trenberth, for one, still expects us to regress to the mean.

He says this is considered a “strong” La Niña and is still likely to wield influence over the winter as a whole. One clue is ocean temperatures in the central-to-eastern Pacific, which are running 2 degrees C (3.5 F) below normal. "That only occurs—probably less than 10% of the time, so it’s a relatively rare event and certainly stronger than anything we’ve seen in recent years," said Trenberth.

Piece also included a great image of the Pinepple Express, in unexpected full bloom:


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