Issued July 29, 2011, Vol. 7, Issue 5

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


July 2011 Summary

Temperature June temperatures were generally below average across Utah and Wyoming but above average across Colorado.

Precipitation June precipitation was well below average in southern Colorado and Utah and average to above-average to the north.

Hydrological Conditions As expected, the above-average to record snowpacks observed across the region in late spring delivered above-average runoff, with flooding in many locations. Reservoirs across the region filled or improved to levels not seen in several years.

ENSO The La Niña event ended in May, and ENSO-neutral conditions are forecasted to continue through the summer season.

Climate Forecasts For August and subsequent seasons, the CPC seasonal outlooks call for an enhanced probability of warmer conditions in the southern portions of the region, and an enhanced probability of wetter conditions in the northern and eastern portions of the region.

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Feature Article

Examining Regional Climate Model (RCM) projections: What do they add to our picture of future climate in the region?

By Karen Cozzetto, Imtiaz Rangwala, and Jeff Lukas

(download pdf)

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Focus Article

There is no Focus Article this month.

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Recent Climate Conditions

Average temperatures for the month of June were near average across much of Colorado, with increases of about 2-4°F above average in the southeastern portion of the state. On the other hand, most of Utah and Wyoming experienced temperatures 2–4°F below average for the month (Figure RC-2). Temperatures ranged from an average of 70–75°F in southeastern Colorado to under 50°F in the mountains of central Colorado and in the Yellowstone region of northwestern Wyoming (Figure RC-1).


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


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


Precipitation during June followed a northeast-southwest gradient, with less than 40 percent of average precipitation falling across much of Utah and southern Colorado, while areas of eastern Utah,and Wyoming, and the Medicine Bow mountains saw over 150 percent of average precipitation (Figure RC3 and RC-4a). For the water-year-to-date, most of Utah, northwestern Colorado and western Wyoming have received 150 percent or more of average precipitation, while southeastern Colorado has received less than 70 percent of average (Figure RC-4b).


 

RC-3

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

RC-4

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

RC-4b

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

 


The 3-month SPI as of the end of June 2011 (Figure RC-5) indicates very dry conditions across southeastern Colorado. Almost all of Wyoming and Utah, however, was moderately to extremely wet for the same period, with near-normal conditions in eastern Utah and across much of Colorado. The 36-month SPI, on the other hand (Figure RC-6), shows near-normal conditions throughout most of the three-state region. Eastern and southeastern Wyoming was moderately to extremely wet over that period, with moderately wet conditions in northern Utah and northeast Colorado. The south-central portion of Colorado remained moderately dry.



RC-5

Figure RC-5. 3-month Intermountain West regional Standardized Precipitation Index as of the end of June 2011 (data from 4/01/11– 6/30/11). (Source: Western Regional Climate Center)

RC-6

Figure RC-6. 36-month Intermountain West regional Standardized Precipitation Index as of the end of June 2011 (data from 07/01/08–6/30/11). (Source: Western Regional Climate Center)

 


The U.S. Drought Monitor for July 19 shows Extreme (D3) and Severe Drought (D2) conditions across most of southeastern Colorado, an extension of the large drought area covering much of New Mexico, Texas, and Oklahoma. The remainder of the three-state region, however, does not contain any drought areas, and only the far southeastern corner of Utah is abnormally dry at this time (Figure RC-7).


 

RC-7

 

Figure RC-7. Drought Monitor from July 19, 2011 (full size) and June 14, 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 and Streamflow

The very large snowpacks observed in late spring across the region finally melted out, after persisting well into July in many locations. The meltout was prolonged by intermittently cool weather at higher elevations in June, with some additional snow accumulation, and the absence of a very warm spell as occurred in early June 2010. Also, the overall impact of dust-on-snow appeared to be less than in 2009 and 2010, except perhaps in southern Colorado where spring accumulation was much less and the dust was exposed more often during the melt season.

The May 1 forecasts for spring and summer streamflow, which called for above-average to well-above-average flow in nearly all basins regionwide, generally verified as observed flow volumes through late July were consistently above average, and in many locations, daily flows were high-for-date during some or most of the runoff season. The observed inflows to Lake Powell for June ended up lower than the last forecast but were still well above average. Snowmelt-induced flooding occured in many locations across the region, particularly in northwest Colorado and northern Utah.

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

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Reservoir Supply

The above-average runoff volumes through June saw reservoir status improve regionwide, with even Lake Powell, which had been well below average during most of the past decade, climbing back up to 76% full and 93% of the long-term average for the end of June (Figure RES-1). Across the region, reservoir levels are the highest since the early 2000s.


  Reservoir Current storage (af) Capacity (af) % Full Average on 6/30 % of Average
COLORADO Dillon Reservoir 255,876 257,304 99% 249,000 103%
Turquoise Lake 116,562 129,390 90% 116,562 100%
Lake Granby 530,296 539,758 98%  432,955 122%
Blue Mesa 828,044 829,500 100%  695,200 119%
Pueblo 222,687 235,000 67%  160,500 139%
             
UTAH Strawberry 1,110,300 1,106,500 100%  710,000 156%
Utah Lake 1,080,000 870,900 124%  872,200 124%
Bear Lake 985,900  1,302,000 76%  972,100 101%
Lake Powell 18,388,080 24,322,000 76%  19,801,000 93%
             
WYOMING Fontenelle 274,058 344,800 79%  271,100 101%
Flaming Gorge 3,525,692 3,749,000 94%  3,235,000 109%
Seminoe 935,129 1,017,273 92%  827,800 113%
Boysen 794,635 741,594 107%  714,600 111%
Buffalo Bill 626,204 644,126 97% 550,000 114%

Figure RES-1. All reservoir content data is from June 30, 2011. Percent of average ranges are color-coded as follows: green: >90%; light green: 60–89%; yellow: 40–59%; orange: 20–39%; red: 0–19%.


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

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ENSO Status and Forecast

The La Niña event of 2010-2011 ended in May with the warming of sea surface temperatures in the tropical Pacific, and ENSO-neutral conditions are currently being observed (Figure EN-1).


EN-1

Figure EN-1. Observed SST (lower) and the observed SST anomalies (upper) in the 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 July 13, 2011. (Source: NOAA Climate Prediction Center)


Model forecasts of SST anomalies (Figure EN-2) reflect a strong consensus that ENSO-neutral conditions will continue through the summer period (July–September). Through the end of 2011, the ensemble of forecasts also point to the continuation of neutral conditions, though with some chance of the emergence of El Niño conditions or the re-establishment of La Niña conditions.


EN-2

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 July–September 2011 to March–May 2012 (released July 20, 2011). (Source: International Research Institute (IRI) for Climate and Society)

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

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Temperature Outlook
August–December 2011 (Released July 21, 2011)

The latest temperature outlooks from the NOAA Climate Prediction Center indicate an enhanced probability of warmer-than-average temperatures in parts or all of Utah and Colorado in August 2011 and subsequent seasons through December (Figures TEMP-1 through TEMP-4). Northern Wyoming, conversely, is indicated to have an enhanced probability of colder-than-average temperatures in August and the August–October season.

The increased odds of warm temperatures in the southern and southwestern US indicated in these forecasts reflects both the continuation of the long-term trend towards warmer temperatures in the region and the typical pattern in fall seen following La Niña conditions.

The August 2011 temperature forecast will be updated on July 31st on the CPC web page. This “zero-lead” monthly update will incorporate information from the short-range numerical weather prediction models and the latest monthly predictions from the Climate Forecast System models. The Seasonal Outlooks are updated on the third Thursday of the month, and the next one will be issued on August 19th.


TEMP-1

Figure TEMP-1. Long-lead national temperature forecast for August 2011. (Source: NOAA Climate Prediction Center)

TEMP-2

Figure TEMP-2. Long-lead national temperature forecast for August–October 2011. (Source: NOAA Climate Prediction Center)

TEMP-3

Figure TEMP-3. Long-lead national temperature forecast for September–November 2011. (Source: NOAA Climate Prediction Center)

TEMP-4

Figure TEMP-4. Long-lead national temperature forecast for October–December 2011. (Source: NOAA Climate Prediction Center)

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

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Precipitation Outlook
August–December 2011 (Released on July 21, 2011)

The CPC precipitation outlooks for August 2011 and the subsequent seasons (Figures PPT-1 through PPT-4) indicate an enhanced probability of above-average precipitation over the northern and eastern portions of the region, including parts of Wyoming and Colorado. These seasonal precipitation forecasts are based on the Climate Forecast System models, ENSO composites, and precipitation trends.

The August 2011 precipitation forecast will be updated on July 31st on the CPC web page. This “zero-lead” monthly update will incorporate information from the short range numerical weather prediction models and the latest monthly predictions from the Climate Forecast System models. The Seasonal Outlooks are updated on the third Thursday of the month, and the next one will be issued on August 19th.


PPT-1

Figure PPT-1. Long-lead national precipitation forecast for August 2011. (Source: NOAA Climate Prediction Center)

PPT-2

Figure PPT-2. Long-lead national precipitation forecast for August–October 2011. (Source: NOAA Climate Prediction Center)

PPT-3

Figure PPT-3. Long-lead national precipitation forecast for September–November 2011. (Source: NOAA Climate Prediction Center)

PPT-4

Figure PPT-4. Long-lead national precipitation forecast for October–December 2011. (Source: NOAA Climate Prediction Center)

 

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

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Seasonal Drought Outlook
through October 2011 (Released July 21, 2011)

The U.S. Seasonal Drought Outlook (DO) builds on the Drought Monitor categories to project how these drought areas might change or where new drought areas might develop. Southeastern Colorado, currently experiencing severe (D2) and extreme (D3) drought conditions, is projected to see improvement in those conditions over the next three months (Figure DO-1). Drought conditions are not expected to develop elsewhere in the region.

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 August 4th.


DO-1

Figure DO-1. Seasonal Drought Outlook for July 21, 2011–October 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.