Issued October 12, 2011, Vol. 7, Issue 6

Brad Udall – WWA Director
Jeff Lukas, Eric Gordon, Kristen Averyt, Tim Bardsley – Editors/Writers
Klaus Wolter, Gary Bates – Asst. Editors


October 2011 Summary

Temperature Temperatures for September were warmer than average across nearly all of the region.

Precipitation September was generally drier than average across the region, and especially dry in Wyoming, northern Utah, and southeastern Colorado.

ENSO After a brief hiatus this summer, La Niña conditions have re-emerged and are expected to persist through the winter season.

Climate Outlooks Consistent with the La Niña conditions, in the late fall and winter seasons, the CPC seasonal outlooks call for some enhanced risk of warmer and drier conditions in the extreme southern portions of our region, and of wetter conditions in the northern portions.

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Announcements & News

Do you need information about the socioeconomic impacts of climate variability and climate change? Let us know!

The WWA-funded “Socioeconomic Impacts and Adaptation Strategies Clearinghouse” project is compiling existing research and studies about the social and economic impacts of and adaptations to climate variability and climate change, relevant to the WWA region (Colorado, Utah and Wyoming), into an online, searchable database. The purpose of the project is to provide useful, readily accessible socioeconomic impacts information to decision makers as they prepare to adapt to climate variability and change. Climate-induced socioeconomic impacts could include:

Please let us know which social and economic impacts you need more information about as you plan for climate variability and change. If published research in that area exists, we will add it to the database. If it doesn’t, we will add it to a roster of research needs and explore options for funding that research. Contact Bobbie Klein at bklein@colorado.edu.


Utah Bark Beetles and Watersheds Workshop -- December 1, Salt Lake City

We invite our IWCS readers in Utah to join the Western Water Assessment (WWA) and the USDA Forest Service Intermountain Region for an all-day science workshop exploring the water-related impacts of bark beetle infestations in Utah and the Rocky Mountain West. Beetle-impacts researchers from WWA, the University of Colorado, and the USFS Rocky Mountain Research Station will present their findings. Researchers, water managers, forest managers, and other decision-makers are encouraged to attend. Please RSVP to Tim Bardsley (wwa.bardsley@gmail.com) by November 23, and specify if you will be attending in Salt Lake City or via videoconference. Space is limited. For more information, go to the WWA Beetles, Water, and Climate web page. (Note: We will also have a 3rd annual beetle-water science symposium in spring 2012 in Boulder, CO--look for announcements after the new year.)

NIDIS Upper Colorado Pilot activities extended, including CCC Upper Colorado drought webinars

The National Integrated Drought Information System (NIDIS) program office has announced that although the NIDIS Upper Colorado Pilot program has formally ended, some activities which were initiated during the pilot will continue. In particular, the CSU Colorado Climate Center has been funded for three years to continue their weekly-to-monthly (depending on time of year) half-hour webinars that present the status of precipitation, snowpack, streamflow, water demand, and drought indices for the upper Upper Colorado basin. Many of the graphics and updates cover the entire three-state region of Colorado, Utah, and Wyoming. To register for the next webinar, go here. The webinars are archived shortly after presentation here.


Changes in this month's IWCS

We usually release the IWCS around the 25th of the month, shortly after NOAA CPC posts its monthly and seasonal climate outlooks on the 3rd Thursday of the month. However, this means that the information released on or about the 1st of the month (previous month's temperature and precipitation, streamflow forecasts, basinwide snowpack maps) is almost four weeks old by the time the IWCS comes out.

We are experimenting this month with an earlier release (by about two weeks) of the IWCS, which will make the first-of-the-month information more timely. Conversely, the monthly and seasonal CPC outlooks are now less timely, having been released the 3rd Thursday of the previous month. Please let us know if you prefer one release date over the other.

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Feature Article

The National Climate Assessment – Available and forthcoming resources for the Intermountain West and beyond

by Jeff Lukas, WWA

(download pdf)

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Focus Article

There is no Focus Article for this issue.


Recent Climate Conditions

Temperatures for September were warmer than average across nearly all of the Intermountain West (Figures RC-1 and RC-2). Warm anomalies of more than 4°F above average occurred in portions of Wyoming and Utah, while pockets of below-average temperatures were most prevalent in eastern Colorado.


Figure RC-1. Average temperature for the month of September 2011 in °F. (Source: High Plains Regional Climate Center)

Figure RC-2. Departure from average temperature for the month of September 2011 in °F. (Source: High Plains Regional Climate Center)


September precipitation was generally below average across the region, especially in much of Wyoming, northern Utah, and southeastern Colorado, where less than 40% of average September precipitation was recorded (Figures RC-3 and RC-4). The only wet anomalies of note were in parts of southern Utah and east-central Colorado; the latter reflects a single storm on September 14 that dropped up to 6" of rain in the Colorado Springs area.


Figure RC-3. Precipitation for the month of September 2011 (inches). (Source: NOAA ESRL Physical Science Division)

Figure RC-4. Precipitation for the month of September 2011 as percent of average precipitation for September. (Source: NOAA ESRL Physical Science Division)


For the 2011 water year that just ended, the region on balance saw wetter-than-average conditions, with more than 150% of average precipitation occurring in much of northern and western Utah, southwestern Wyoming, and northwestern Colorado. Most of this widespread wet anomaly occurred during the DecemberMay period as the storm tracks consistently favored those regions, leading to record snowpacks in many mountain locations. Both Utah and Colorado experienced a strong gradient from wet conditions in the northwest to dry in the southeast, with southeastern Colorado seeing less than 70% of average precipitation for the water year.


Figure RC-4b. Precipitation for the 2011 water year (October 2010–September 2011) as percent of average precipitation for that period. (Source: NOAA ESRL Physical Science Division)


The 3-month SPI (Figure RC-5) as of October 1 indicated near-normal conditions across Colorado and most of Utah, with moderately wet conditions in northeastern Utah. Dry conditions in August and September were balanced out by a wet July in those two states. Wyoming, however, was on the dry side over the past three months, with very dry to extremely dry conditions in the northern part of the state.

The 36-month SPI (Figure RC-6) indicated either near-normal or moderately wet long-term conditions across the entire region, with the exception of moderately dry conditions in south-central Colorado and very wet conditions in east-central Wyoming.



    

Figure RC-5. 3-month Intermountain West regional Standardized Precipitation Index as of the end of September 2011 (data from 7/1/11–9/30/11). (Source: Western Regional Climate Center)

   

Figure RC-6. 36-month Intermountain West regional Standardized Precipitation Index as of the end of September 2011 (data from 10/01/08–9/30/11). (Source: Western Regional Climate Center)


The U.S. Drought Monitor issued October 4 indicated that the extreme (D4) and severe (D3) drought conditions in southern Colorado have been partly alleviated since mid-July, though a large portion of the state is still in drought (Figure RC-7). A small area of abnormally dry (D0) conditions has persisted in extreme southeastern Utah, and a new area of abnormally dry conditions has emerged in eastern Wyoming.


Figure RC-7. Drought Monitor from October 4, 2011 (full size) and July 19, 2011 (inset, lower left) for comparison. (Source: National Drought Mitigation Center)


Notes & Weblinks
(provides explanations of graphics and additional information sources)

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Intermountain West Snowpack

Snowpack levels during October reflect the beginning of the winter snowpack accumulation and are poorly correlated with peak snowpack levels. However, October precipitation and snowfall can be important for alleviating summertime drying of the soil, potentially improving runoff efficiency in the following spring, and for establishing the snow base at regional ski areas.

After a large and moist storm system moved through the region during the first week of October, as of October 10, most higher-elevation SNOTEL sites throughout the region showed well-above-average SWE for the date (Figure SP-1). While this looks like a promising start to the season, bear in mind that the actual SWE amounts at nearly all sites are less than 2”, with some sites in southwestern Colorado, northeastern Utah, and central Wyoming having up to 4”.


Figure SP-1. Snow-water equivalent as of October 10, 2011 as percent of the long-term average, at SNOTEL sites across the Intermountain West. (Source: Natural Resources Conservation Service)

Notes & Weblinks
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ENSO Status and Forecast

The end of a moderate to strong La Niña episode in early May 2011 was followed by neutral ENSO conditions until August, when weak La Niña conditions returned. This "double-dip" La Niña behavior—diminishing during summer and reappearing in fall—has occasionally occurred in the past, most recently in 2008.


Figure EN-1. Observed SST (upper) and observed SST anomalies (lower) in the tropical Pacific Ocean.  The Niño 3.4 region encompasses the area between 120°W–170°W and 5°N–5°S.  The graphics represent the 7-day average centered on September 28, 2011. (Source: NOAA Climate Prediction Center)


Model forecasts made in late summer of SST anomalies as compiled by the International Research Institute for Climate and Society (IRI) reflect a nearly even split between models projecting a continuation of La Niña conditions throught the winter, and those projecting a return to ENSO-neutral conditions (Figure EN-2). Note that this set was compiled in mid-September from forecasts made earlier; the next set of forecasts, to be released October 20th, should show a greater likelihood of continuing La Niña conditions, given more than a month of recent observations of cooling SSTs like those shown in Figure EN-1.


Figure EN-2. Forecasts made by dynamical and statistical models for sea surface temperatures (SST) in the Niño 3.4 region for nine overlapping 3-month periods from September–November 2011 to May–July 2012 (released September 15, 2011). (Source: International Research Institute (IRI) for Climate and Society)

Notes & Weblinks
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Temperature Outlook
October 2011–February 2012

The latest temperature outlooks from the NOAA Climate Prediction Center indicate an enhanced risk of below-average temperatures across the western portions of the Intermountain West in October 2011, shifting to an enhanced risk of above-average temperatures in the southern part of the region for the November-January season, consistent with typical La Niña impacts (Figures TEMP-1 and TEMP-2). In the subsequent season, this area of enhanced risk of warm temperatures shifts to the south and east (Figure TEMP-3).

Temperature impacts of La Niña over the U.S. are typically weaker during the summer and early fall, and strengthen during the late fall and winter.  The ENSO state heavily influences the outlooks for temperature for November and subsequent seasons through the winter. The monthly outlook for October blends both long-term climate forecasts with shorter-term (up to 14-day) weather forecasts. There is also an overall trend towards warming conditions in the southwestern U.S. that is incorporated into the forecasts.

Note: These climate outlooks are intended for use prior to the start of their valid period (in this case, prior to the beginning of November).  Within any given valid period, observations and NWS short- and medium-range forecasts should be consulted. The zero-lead monthly outlook and the seasonal outlooks are updated on the third Thursday of the month, and the next ones will be issued on October 20th.


Figure TEMP-1. Long-lead national temperature forecast for October 2011 (released September 30, 2011). (Source: NOAA Climate Prediction Center)

Figure TEMP-2. Long-lead national temperature forecast for November 2011–January 2012 (released September 15, 2011). (Source: NOAA Climate Prediction Center)

Figure TEMP-3. Long-lead national temperature forecast for December 2011–February 2012 (released September 15, 2011). (Source: NOAA Climate Prediction Center)

 

Notes & Weblinks
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Precipitation Outlook
October 2011–February 2012

The CPC precipitation outlook for October 2011 (Figure PPT-1) shows a slightly enhanced risk of wetter-than average conditions in Wyoming, with no shift in probability elsewhere in the region. For the November–January and December–February seasons, this region of enhanced risk of wetter conditions contracts to western Wyoming (Figure PPT-2), and then expands again into northern Utah and Colorado (Figure PPT-3). Meanwhile, enhanced risk of drier-than-average conditions lurk to the south of our region, extending into far southern Utah and Colorado in the November–January season.

The areas of above- or below-median precipitation described above are largely due to expected La Niña impacts on climate, including the typical La Niña-influenced tilt of the odds towards below-median precipitation for some areas of the southern tier and towards wet conditions for the Pacific Northwest. The monthly outlook for October blends both long-term climate forecasts with shorter-term (up to 14-day) weather forecasts.

Note: these climate outlooks are intended for use prior to the start of their valid period (in this case, prior to the beginning of November).  Within any given valid period observations and NWS short- and medium-range forecasts should be consulted. The zero-lead monthly outlook and the seasonal outlooks are updated on the third Thursday of the month, and the next ones will be issued on October 20th.


Figure PPT-1. Long-lead national precipitation forecast for October 2011 (released September 30, 2011). (Source: NOAA Climate Prediction Center)

Figure PPT-2. Long-lead national precipitation forecast for November 2011–January 2012 (released September 15, 2011). (Source: NOAA Climate Prediction Center)

Figure PPT-3. Long-lead national precipitation forecast for December 2011–February 2012 (released September 15, 2011). (Source: NOAA Climate Prediction Center)

 


According to the experimental PSD Precipitation Forecast Guidance released in late September, the OctoberDecember season has a slight tilt towards drier-than-average conditions over the plains of eastern Colorado, with a stronger tilt (510%) over south-central Colorado (Figure PPT-5a). The JanuaryMarch season has a
more widespread tilt towards dryness in both Utah and Colorado, especially over northwestern Utah and southeastern Colorado (510%) (Figure PPT-5b). While not explicitly factored into these forecast maps, they confirm a general tendency in our region for the second consecutive year with cold-season La Niña conditions to be drier than the first year.  Thus, a repeat of last year's (near-) record snowpacks in the higher elevations
of Colorado and Utah is unlikely.


 

Figure PPT-5a. Experimental precipitation forecast guidance. Forecasted shifts in tercile probabilities for October–December 2011. (Source: NOAA ESRL Physical Science Division)

 

Figure PPT-5b. Experimental precipitation forecast guidance. Forecasted shifts in tercile probabilities for January–March 2012. (Source: NOAA ESRL Physical Science Division)

 

Notes & Weblinks
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Seasonal Drought Outlook
through December 2011 (Released September 15, 2011)

The U.S. Seasonal Drought Outlook (DO) projects how drought areas categorized in the U.S. Drought Monitor might change and where new drought areas might develop. The Drought Outlook released in mid-September forecasts that the area of drought in southeastern Colorado will improve over the next three months, but drought conditions will develop just to the west, in southwestern Colorado and southeastern Utah.

Readers interested in the next 1–5 days and 6–10 days can consult the “Looking Ahead” section of each week’s Drought Monitor for near-term drought outlook conditions. The next Seasonal Drought Outlook will be issued October 20th.

Figure DO-1. Seasonal Drought Outlook for September 15, 2011–December 2011. (Source: NOAA Climate Prediction Center)

Notes & Weblinks
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The Intermountain West Climate Summary is published periodically by Western Water Assessment (WWA), a joint project of the University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES) and the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL), researching water, climate, and societal interaction.

Disclaimer - This product is designed for the provision of experimental climate services. While we attempt to verify this information, we do not warrant the accuracy of any of these materials. The user assumes the entire risk related to the use of this data. WWA disclaims any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. This publication was prepared by CIRES/WWA with support in part from the U.S. Department of Commerce/NOAA, under cooperative agreement NA17RJ1229 and other grants. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of NOAA.