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Posted at 10:45 AM ET, 11/ 3/2009

Remarkable fall storm showed links to El Niño

By Andrew Freedman

* Full Forecast | October recap | This week: Our Winter Outlook *


Snowfall amounts from Oct. 27-29 in north and northeast Colorado. Courtesy of NOAA/National Weather Service.

Two images capture a remarkable storm that dumped record snow last week in Colorado, flooded parts of the South Central states, and spawned an EF-2 tornado that tore through downtown Shreveport, La. (population 200,000).

The first image (above) shows the absolutely phenomenal snowfall totals in Colorado, where accumulations of one to two feet were common in the Front Range metro areas, including Denver and Boulder. The jackpot was found in the mountains and foothills to the west and northwest of Denver, with 46 inches of snow recorded near Pinecliffe.

Keep in mind that this snowstorm occurred at the same time baseball's World Series kicked off -- a period most people typically call "fall." It was a bit early for 46 inches of snow, don't you think?

The other image (below) shows the wet side of the storm, with an unbroken band of heavy rain that fell Oct. 29-31, stretching from northeast Texas through southern Illinois. The widespread three to six inches of rain fell on already saturated ground, and flash flooding and river flooding ensued.


Three-day rainfall totals for the South Central U.S., ending on Nov. 1, 2009. Courtesy of NOAA/National Weather Service.

The 5.88 inches of rain that fell in Shreveport on Oct. 29 was the seventh wettest 24-hour rainfall total on record for that city, according to Victor Murphy, Climate Service Program Manager for the National Weather Service Southern Region in Fort Worth, Texas.

More significant than the single event, however, was how it aggravated preexisting flooding concerns. The storm pushed the water-logged Arkansas/Louisiana/Texas border area -- known as the "ArkLaTex" -- well into record territory for October, following an unusually wet September. October 2009 was the wettest on record in Shreveport and Monroe, La., as well as in Tyler, Texas, and El Dorado, Ark.

With 20.35 inches of rain, Shreveport broke its previous October record by more than six inches, and even recorded its third wettest month overall since records began in 1930.

"These periods would be the wettest 30- and 60-day periods for this time of year for these areas dating back to 1895," Murphy said in an email conversation.

Links to El Niño

While specific weather events cannot be definitively linked to large-scale climate factors, the storm, and the unusually wet fall season in parts of the nation's mid-section, may have had ties to a well-known source of natural climate variability -- our old friend El Niño, currently lurking in the tropical Pacific Ocean.

An El Niño event is characterized by warmer-than-normal sea-surface temperatures in the central and eastern equatorial Pacific. El Niño can lead to significant shifts in weather patterns worldwide.

As occasional CWG contributor Robert Henson of the University Corporation for Atmospheric Research (UCAR) explains in the current edition of UCAR Magazine, El Niño is associated with heavy early-season snowstorms in Colorado.

"...the presence of El Niño boosts the odds of a big dump considerably, even though our winters as a whole aren't substantially wetter during El Niño," Henson wrote. "It's a good example of nuance in the relationship between El Niño and climate, the kind of connections worth exploring in many parts of the world."

According to Henson, research shows almost half of the major snowstorms (12 inches plus) in Boulder occurred in El Niño years, compared to only 22 percent during El Niño's opposite phase, La Niña. Even heavier snowstorms, on the order of 20 or more inches, are almost seven times more likely to occur in an El Niño year compared to non-El Niño years. In addition, El Niño winters tend to bring more snows in the early and late parts of the season, with a dry spell in between.

However, the Weather Service's Murphy said the storm that buried Colorado and flooded the ArkLaTex did not feature the hallmarks of a typical El Niño-related event, such as a subtropical jet stream feeding Pacific moisture into the southern U.S. He also noted that "the impacts of El Niño are most commonly felt deeper into the winter and spring (i.e. mainly from November into March or April)," rather than during the fall.

"On the other hand, this El Niño continues to strengthen. If the El Niño weren't in place, would this event have been less likely to occur? Probably," Murphy said.

Connections with climate change?

There is another elephant in the room that may have played a role in the numerous rounds of rainfall that have contributed to a historically wet fall in the ArkLaTex, and to the heavy snowfall in Colorado: manmade climate change. Like El Niño, climate change does not cause a particular weather event, but it can increase the odds that events will pass certain thresholds, kind of like how taking performance-enhancing drugs may increase the odds of a baseball player hitting a home run.

According to Murphy, this was Louisiana's wettest October on record, and Arkansas may have recorded its wettest as well. The monthly values for both September and October in these two states constitute roughly a one in 100-year event for this time of year, Murphy told me.

We know from numerous studies, including a 2008 federal report on climate extremes, that climate change increases the odds of heavy rain events. That report showed that the nature of rainfall in North America, how heavy it is and how often it occurs, has shifted during the past century to favor heavier downpours. The report tied this change to the increase of water vapor in the atmosphere that has occurred as a feedback to warming from greenhouse-gas emissions.

However, the evidence tying climate change to the recent historic wet spell, and to last week's storm in particular, is not as strong as the potential link to El Niño. El Niño has strengthened throughout the fall, potentially increasing its impacts on U.S. weather patterns.

As will be detailed in CWG's winter outlook later this week, El Niño may play a big part in determining whether our winter will be a particularly white one, or if D.C. area snow lovers are going to be disappointed yet again.

The views expressed here are the author's alone and do not represent any position of the Washington Post, its news staff or the Capital Weather Gang.

By Andrew Freedman  | November 3, 2009; 10:45 AM ET
Categories:  Climate Change, Freedman, News & Notes, Science  
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Comments

I can personally attest that we received 22.3" of snow in Boulder, and that it snowed (in varying rates of intensity) for 47 hours straight!

Posted by: Josh-CapitalWeatherGang | November 3, 2009 11:27 AM | Report abuse

Typically Colorado seems to have its heaviest snowfall early and late in the winter season, while midwinter can be relatively cold and dry--a reflection of Colorado's continental climate.

This scenario is evidently amplified during an El Nino winter, as storms moving in from California can dump their excess snow on the Wasatch and Rocky Mountains. There may be no dry midwinter interlude during an El Nino winter.

Posted by: Bombo47jea | November 3, 2009 1:56 PM | Report abuse

I am curious about something Mr. Freedman. If you had to choose between -
a. getting a root canal without any anesthesia
or
b. having a long, in depth discussion (let's say your next 7 columns, spanning the next 5 weeks) about the proposed political solutions to "climate change" and how those solutions will affect the average American

Which would you choose?

And why do you refuse to discuss "global warming" policies?

Is it because if people knew some of the proposed solutions being discussed, they would demand a higher standard of proof?

Mr. Q.

Posted by: Mr_Q | November 4, 2009 12:40 PM | Report abuse

Senator Barbara Boxer us gave a peek at her thought processes. According to Senator Boxer, unemployment is great for the climate.

Not only does that lady have her priorities backwards, she is incredibly short sighted. The wealthier a nation the better that nation's environment. That is an indisputable fact. The population of the poorer countries are too worried about survival to care much about the environment. So if you really want to help the environment, lift the poor countries out of poverty.

Mr. Q.

Posted by: Mr_Q | November 4, 2009 12:55 PM | Report abuse

@Mr. Q--

The climate change coverage on this blog focuses on scientific issues...Andrew doesn't cover policy solutions b/c that's really outside the scope of this blog.

Posted by: CapitalWeatherGang | November 4, 2009 10:45 PM | Report abuse

CapitalWeatherGang wrote, "...Andrew doesn't cover the policy solutions of things b/c that's really outside the scope of this blog."

And who set the scope of this blog?

Mr. Q.

Posted by: Mr_Q | November 4, 2009 10:47 PM | Report abuse

According to what Dan Stillman posted here, the scope of this blog includes -
"Commentary on climate change and environmental science."

How does discussing the proposed climate change policy solutions fall outside of the scope of "Commentary on climate change"?

Mr. Q.

Posted by: Mr_Q | November 4, 2009 10:53 PM | Report abuse

@CapitalWeatherGang

If you happen to run into Mr. Stillman, could you please pass along a question for him from me?

Please ask him - Do you only write articles about global warming and record temperatures when the records being broken are record highs?

Mr. Q.

Posted by: Mr_Q | November 4, 2009 11:11 PM | Report abuse

CapitalWeatherGang wrote, "The climate change coverage on this blog focuses on scientific issues...Andrew doesn't cover policy solutions b/c that's really outside the scope of this blog."


Let me make sure I understand the scope of this blog where climate change is concerned.

Inside the scope of this blog are the following "scientific issues" related posts/columns -
Wear a Condom... Save the Planet?
Climate Change and the Scary Jellyfish Scourge
Caution: Giant Snakes Ahead
Freedman: In-flight Magazines and Polar Bears
Freedman: Planning Your Global Warming Vacation
Local Poets Slam on Climate Change
Freedman: Time to Play God With Wildlife?
Freedman: Weather Almanacs Grapple with Warming
Weather Channel Cuts Earn Mixed Reviews
Greenpeace Protest Ties Up Traffic; Not So Green
Social Science Uncovering New Climate Angles
Freedman: Climate Change Low on Public Agenda
Global warming poll finds puzzling trend
Renaming Climate Change - Does it Matter
Will an Economic Downturn Benefit the Climate?
Politico Falls Into Climate Coverage Trap
Climate Change & National Security: A Tough Sell
Videos: Freedman, Morano Clash on Climate
Freedman: Hot Weather, Heated Political Rhetoric
Joe Wilson, Civility, and Climate Change
Biden, Palin Clash on Climate Change
Dueling Climate Meetings Aim to Steer Policy
Oval Office Debate on Global Warming?
Obama Needs to Give a Climate Speech - ASAP
Freedman: Three Statistics for Climate Change Talks
Goals of Major U.N. Climate Meeting Unclear


So the "scientific" climate change issues within the scope of this blog include condoms, giant snakes, scary jellyfish, weather almanacs, playing God with wildlife, in-flight magazines, slam poetry, Greenpeace protests, national security, social science, polls, a video debate between Freedman and Morano, the Weather Channel earnings, the effect on climate of our economic downturn, the Politco, Sarah Palin, Joe Wilson, and the "Goals" of a Major U.N. climate meeting. But it does NOT include any discussion of proposed policies to reduce CO2.

Am I the only one who finds this inexplicable?

Mr. Q.

Posted by: Mr_Q | November 5, 2009 12:32 PM | Report abuse

The comments to this entry are closed.

 
 
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