More evidence La Niña will return

Following WUWT’s story on 8/22, we have this from the University of Arizona

Evidence Suggests La Niña Will Return This Winter

By Zack Guido and Mike Crimmins, CLIMAS, August 23, 2011

A return of La Nina, which historically delivers dry conditions, is increasingly likely.

Blame it on La Niña.

Pushing the jet stream and the storms it carried north of the region, La Niña played a starring role in a record-dry winter in the Southwest this past year.

The lack of rain and snow led to extensive fires in Arizona and New Mexico, skimpy irrigation allotments and withered vegetation in the spring. Now mounting evidence suggests that after a brief summer hiatus La Niña may be back.

This would not be welcome news for most of the Southwest, and especially those areas mired in extreme and exceptional drought, particularly since the second year in back-to-back La Niña events is often drier than the first.

During the 20 winters since 1950 in which La Niña was present, precipitation has been, on average, below-average across the region. Last winter upheld this dry pattern, as a moderate to strong La Niña event developed in June 2010 and dissipated in April.

At the onset of winter, in the beginning of November, only about 3 percent of Arizona was classified with moderate drought conditions; New Mexico was drought-free. By the beginning of the 2011 monsoon season in mid-June, however, 56 and 99 percent of Arizona and New Mexico, respectively, were in the grips of moderate, if not more severe, drought.

Drought also intensified in nearly every region. By mid-June, nearly 6 and 45 percent of Arizona and New Mexico, respectively, were pegged with the most severe drought category – exceptional drought, which occurs once in every 50 years; about another 13 and 23 percent were classified with extreme drought, which occurs once in every 20 years.

With the region desiccated in the lead-up to the summer rains, climatologists at the University of Arizona and National Drought Mitigation Center at the University of Nebraska stated that an average monsoon season would be insufficient to significantly improve drought conditions.

The region needed constant and copious moisture. In most of New Mexico and all of Texas, the October-July period was either the first or second driest in the last 117 years, while southeast Arizona ranked in the top six.

La Nina 3(Click image to enlarge) Average November-March precipitation during the 20 winters since 1950 in which a La Niña event was present. Map is from WestMap and utilizes PRISM (Parameter-elevation Regressions on Independent Slopes Model) data.

To date, however, the thunderous storms have been inconsistent and spottier than usual, and most of the region continues to accumulate rainfall deficits. It is unlikely that summer rains will provide widespread drought relief this late in the season.

The NOAA-Climate Prediction Center, or CPC, assigns less than a 3 percent chance that moisture in the upcoming four months will be sufficient to erase drought conditions in southern Arizona and New Mexico where drought conditions are most severe.

This doesn’t bode well for the region.

“The bigger the droughts are, the longer they last,” said Klaus Wolter, research scientist at the Climate Diagnostics Center at the University of Colorado. “I think when you have a big drought it can perpetuate itself.”

Another La Niña would only exacerbate the situation.

In July, the CPC issued a La Niña Watch, indicating favorable conditions for the development of another La Niña event in the next six months. With colder-than-average waters once again upwelling in the tropical Pacific Ocean, La Niña appears to be re-forming.

“Temperatures below the sea surface have decreased quite markedly in the last few months,” said David Unger, meteorologist at the CPC.

In addition, he said, the Climate Forecast System model – a state-of-the-art climate model that integrates interactions between the Earth’s oceans, land, and atmosphere – has been impressive in its prediction capabilities in the last few years and has been increasingly more confident in the development of a La Niña this winter.

“It’s close to even odds right now that La Niña or neutral conditions will develop,” Unger said. “It’s pretty trivial chances that El Niño will form.”

The International Research Institute for Climate and Society, or IRI, also indicates increasing odds for a return of La Niña. Basted on statistical and dynamicla models and conditions that developed in the last week, there is a 43 percent chance that La Niña will develop during the October-December period, an increase from 25 percent assigned last month to this period.

Historically speaking, back-to-back La Niña events are not surprising. The climate system tends to have a more difficult time shedding a moderate or strong La Niña event than a weaker one. An intense La Niña tends to persist for multiple years; one even lasted for 34 consecutive months between 1954 and 1957.

A La Niña event may return the following fall season even if it weakened or disappeared during the summer, as was the case this summer, Wolter said.

His insight, detailed in his experimental forecast discussion, lies in looking at past La Niña events that, like last winter’s event, had rapid onsets and were associated with very cold sea surface temperatures anomalies. Dynamical and statistical climate models are now starting to agree with Wolter, but he thinks this event will be less intense than last winter’s.

“My expectation is that this winter’s (La Niña) will be weaker,” Wolter said. “Last winter was the third strongest event, and it will be hard to beat that; it’s an opinion based purely on statistics.”

A weaker event doesn’t necessarily bring wetter conditions than a stronger event, however. Wolter recreated the MEI back to 1870 and found that for the 10 historical cases in which La Niña lasted at least two consecutive years, eight generated lower flows in the Colorado River Basin in the second year.

Lower flows are very likely to happen this year because record snows packed the Upper Colorado River Basin last winter.

Last winter “was the first time since 1917 that the Colorado River had a big runoff year-with more than 20 million acre-feet-in a La Niña event,” Wolter said.

La Niña’s re-emergence isn’t a done deal, however. Forecast models are still mixed despite a growing number suggesting a double-dip, and forecasters are waiting for additional data before increasing the odds of a return to La Niña.

“I’ll continue to look at the subsurface temperatures, which are a leading indicator of La Niña events, and I’ll keep an eye on the models,” Unger said. “In my experience, the best indicator is coherence in models.”

In the next few months, forecasters should have a better idea of the final call: La Niña or neutral conditions. Regardless of which wins out, eastern New Mexico likely will experience a dry winter. Neutral events in this area, along with West Texas, often bring slightly drier conditions, Unger said.

For the rest of the region, southwesterners are crossing their fingers for a neutral event. In the past these events have brought either a wet or a dry winter.

“You don’t have to have a severe dry period to make an existing drought worse,” Wolter said. “I’m concerned about an increased probability of this winter being drier than average.”

h/t to WUWT reader Gary Swift

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August 24, 2011 1:18 pm

To be fair, Dr. Klaus Wolter at NOAA has been forecasting this – a (strong according to his MEI measure) La Niña would return after a summer hiatus – for almost a year.
Dr. Wolter possibly might still be wrong but certainly no kudos to Hansen who was predicting a super-El Niño back in March. “we believe that the system is moving toward a strong El Niño starting this summer.”

August 24, 2011 1:38 pm

Do not forget that “in a warming world, models predicted more frequent and stronger El Ninos”
Then compare it with reality:
What does it take to invalidate those mighty models?

August 24, 2011 1:56 pm

“It’s not a done deal”…..oh, but allow me to retort: “yes it is.”

August 24, 2011 2:24 pm

Enough with La Nina – here in Aus where we were told by experts we’d never have dam filling rains again it has hardly stopped raining since October/November 2010 especially in Queensland.
Who do I see to get a bit of AGW climate change El Nino ? I want some dry weather and a bit of warmth. This winter may not have been the coldest but I can’t remember a longer continuous period of cooler weather since the 70’s.

David Falkner
August 24, 2011 2:28 pm
Thank goodness. Don’t need any more violence in the tropics.

August 24, 2011 3:18 pm

Will the Govt ignore the full dams again next spring?

August 24, 2011 4:15 pm

Bad news for Texas.
Wait for this La Nina-drought to get media attention next year … as propaganda (er, news from the ABCNNBCBS tools) to attack Texas’ governor as representative of an evangelical non-science way of thinking. Obviously, if he supported CAGW thinking like the right-minded and thoroughly-politically corrupt (er, correct) governors of Washington and Oregon and New York and Illinois, then he’d be getting more rain on his state!

August 24, 2011 6:09 pm

I went and identified several La Niña years since 1895 that were, when normalized for long term trends and variance, the twenty most extreme La Niña on record. These offer some analogs for creating composites to see what the weather typically looks like under La Niña conditions. (I also have a similar set of years for El Niño):
I was rather encouraged by my year selection as indicative of La Nina patterns, when the pattern of these composites looked a lot like precipitation and temperature patterns we have seen after this most recent La Nina:
So sad to say it looks like Texas is in for another nasty dry, hot year again, and much of the US will be quite warm as well. Interestingly, the El Niño patterns I get actually also show large areas of the US mostly warm rather than cool. Which means in large parts of the US both phases of ENSO appear to be associated with warm temps. “Something else” must cause cool years in those places. Hm…I wonder…

John F. Hultquist
August 24, 2011 10:16 pm

RACookPE1978 says:
August 24, 2011 at 4:15 pm
“and thoroughly-politically corrupt (er, correct) governors of Washington”

The Governor of Washington State was expecting GW to cause a lack of snow in the mountains and believed in the material she was given. When someone pointed out to her that the trend just wasn’t there, he was told to take his charts and go home. This past winter WA had massive snow fall and late opening of highway passes and buried hiking trails. I wonder if she is paying attention.
Too bad we can’t send a little of our water to Texas. Maybe we can ship some of the fruit and vegetables grown with a more than adequate supply of irrigation water.

August 24, 2011 10:25 pm

My prediction: it’s going to get cold this winter. We may or may not have a lot of snow. I preparing as if we will get a lot of snow & cold. If I’m wrong, I’ll have a head start on next years firewood supply – but I’m betting I won’t. So I’ll be cutting/splitting/stacking more this weekend. Ohio winters have been getting worse since 2007.
Moving along now…

Mac the Knife
August 24, 2011 10:33 pm

RACookPE1978 says:
August 24, 2011 at 4:15 pm
“Bad news for Texas.
Wait for this La Nina-drought to get media attention next year … as propaganda (er, news from the ABCNNBCBS tools) to attack Texas’ governor as representative of an evangelical non-science way of thinking. Obviously, if he supported CAGW thinking like the right-minded and thoroughly-politically corrupt (er, correct) governors of Washington and Oregon and New York and Illinois, then he’d be getting more rain on his state!”
Interesting to note that, while the State of Texas is cutting taxes, balancing their budget and creating fully half of the new jobs in the country, the States of Washington, Oregon, New York, and Illinois are all facing massive debts and deficits, trying to raise taxes, experiencing high unemployment, and dead-as-dog-squeeze economies and tax receipts! They are doing quite a few things right, in Texas…..and they work, where ever they are tried. You can hold Governors and their state legislators accountable for all of the above, but even an idiot would not try to hold them accountable for the weather! Of course, I could be wrong… about the idiots.
As for the near certainty of another long and cold La Nina fall, winter, and spring here in the Great NorthWet (Washington state), I’m adding to the +6 full cords of firewood that I already have split and dry! The north face of Mt. Rainier has retained more snow covered area both last year and again this year, than I have seen in any of the preceding 10 years. Local news reports we have had significantly below normal average temperatures every month since January. The ‘truth’ is staring Seattle right in the face, but “There is none so blind as they who will not see.”

Hector Pascal
August 24, 2011 11:19 pm

My prediction: it’s going to be cold this winter, and we can expect between 10-12 metres of snow. Just like all the seven previous winters I’ve spent in northern Japan. I’ve spent the past 6 weeks re-building all the protective cages housing our factory aircon units and hot water boilers, and converting iced water into sweat and salt stains. Another 2 weeks and I’ll be done. I consider that time well invested.

Larry in Texas
August 25, 2011 2:15 am

Yuck! I was hoping to turn my sprinklers off of automatic this fall and winter. Not good news for down here. But we did have a nice, brief cool-off for a while tonight. A front with storm clouds moved through (brought no rain where I was, unfortunately), the winds shifted abruptly and blew hard, and the temp went down from 104ºF. to about 84º F. within the hour. Sometimes Texas weather can be a really nice air conditioner.

August 25, 2011 3:13 am

When El Niño, ‘The (Christ) Child,’ was first described to be an abnormal circulation I thought the more normal condition might have been called ‘El Padre,’ but now with the understanding that these are two metastable states of equal average duration, the current nomenclature makes more sense. I believe we have now documented the modern period ENSO cycles and the general consequences of each stage of the oscillation, but there has been no explanation of why it is happening. We just appear to be bouncing between to circulation patterns that seem to shut themselves off after a short duration. Perhaps a slowly changing, climate-driving factor will eventually allow one or the other state to become permanent. That factor could be plate-tectonic related.

Steve Keohane
August 25, 2011 4:27 am

The Oct-July Precip. Percentile map seems off. The Colorado river had high flow right through July of this year. The snow pack is still high, and will start increasing soon. We had an abnormally wet summer, monsoons came a month early, and spring rains stopped late. Yet that map shows 66-87.4% of ‘normal’ precip. We have been abnormally wet and NOAA claims we are below normal. Right.

August 25, 2011 4:42 am

More evidence La Niña will return
It never really went away. The rebound from La Nina was as illusory and shortlived as the world economy’s recovery from the credit crisis over the same timescale. Now both the economy and east Pacific sea temperatures are tanking together. Hmmm – wonder if they’re related – folks dont do so much shopping when its cold.

Dave Springer
August 25, 2011 6:21 am

This sucks.
Dryer than a bone in South Central Texas

August 25, 2011 6:34 am

I actually get angry about this. Here we have legions of PhD’s uselessly chanting “Global Warming, Global Warming” when they could be engaged in research which could eventually enable useful climate predictions. But nooooooo! Not if it will debunk our Global Warming pseudo-religion.

August 25, 2011 7:45 am

phlogiston said at 4.42 am. That’s true people don’t shop as much when they can’t get out of snow drifts and flooded causeways.

Septic Matthew
August 25, 2011 10:18 am

Steve Keohane: Yet that map shows 66-87.4% of ‘normal’ precip.
Those are percentiles (compared to local distributions), not percents of average. All the green and blue areas are above median. White is close to median.

August 25, 2011 2:38 pm

Yuck. We really need rain and some cooler weather in Texas. Forget the lawns, even the native trees are drying up and dying.

Steve Keohane
August 25, 2011 8:40 pm

Septic Matthew says: August 25, 2011 at 10:18 am Thank you. So you are saying the colors are indicative of the distribution across the country, as opposed to a comparison of local records.

August 26, 2011 12:02 am

A big change in the SST’s today. Overnight a colder tongue forming off Sth America with the water above New Guinea also warming suddenly, this is a similar format as last May as shown in my animation.
The SST’s of the northern Pacific in deep cold PDO mode, has the hot area in the central northern Pacific been flowing towards New Guinea to strengthen the Walker Cycle? Perhaps one case of the PDO driving ENSO?

August 26, 2011 12:21 am

Meant to say May 2010…

Lawrie Ayres
August 26, 2011 2:53 am

Rosco @ 2.24,
In La Nina years the warm waters of the Pacific pile up against the east coast of Australia while cool water collects adjacent to the Americas. Hence they have drought and we have floods. In El Nino years it reverses. Australia has had a long drought (ten years) in some places so a few floods will balance the average. The Greens reckon the drought was caused by global warming and it would never rain again then the floods were caused by coal mines. Brilliant observers of detail, the Greens. Most come from the inner city and just don’t get nature.

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