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Note: This work is published by the Climate Assessment for the Southwest (CLIMAS) project, The University of Arizona Cooperative Extension, and the State Climate Office at Arizona State University; and is funded by CLIMAS, and the Institute for the Study of Planet Earth.

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Forecasts and Outlooks >Archive
Southwest Climate Outlook - December 2008

Date issued: December 22, 2008

A. Summary

Due to The University of Arizona holiday closure, the full version of the Southwest Climate Outlook will not be produced this month. Please select the PDF file on the right for updated reservoir information and maps. The November 2008 information is still available, and we will be back with a complete version of the SWCO in January 2009. Happy Holidays from the Southwest Climate Outlook staff!

Drought – Short-term drought conditions reported for October in Arizona worsened in many regions, most notably in the Little Colorado River watershed where abnormally dry conditions in September were downgraded to a moderate drought classification; long-term drought status remains the same. In New Mexico, November drought conditions did not change from last month.

Temperature – During the past 30 days, temperatures in Arizona and western New Mexico have been 2 to 6 degrees F warmer than average. The recent storm system that passed through the Southwest on December 16–18 brought colder-than-average temperatures to most of Arizona and northern New Mexico.

Precipitation – Until recently, most of the Southwest had received little precipitation since the beginning of the water year on October 1. However, storms on Thanksgiving and between December 16 and 18 finally brought wetter conditions and delivered record snowfalls in some areas. In the past 30 days, most of Arizona and northern New Mexico have had 100 to 1,200 percent of average precipitation, due entirely to those two storms.

ENSO – The International Research Institute for Climate and Society (IRI) reports that the equatorial Pacific Ocean is presently on the borderline of ENSO-neutral and weak La Niña conditions. The IRI also states there is a 50–55 percent probability of ENSO-neutral conditions persisting over the coming season, and a 45–50 percent chance for weak La Niña conditions.

Snow – The water contained in the snow (snow water equivalent, or SWE) in most watersheds in the Upper Colorado River Basin on December 18 is generally between 70 and 90 percent of the 1971–2000 average. In the headwaters of the Rio Grande, SWE is about 70 percent of the average. Recent storms have elevated SWE in Arizona, with values ranging between 150 and 225 percent near Flagstaff and the central Mogollon Rim.

The Bottom Line – The first winter storms of the 2009 water year finally arrived, providing much needed precipitation that may help alleviate short-term drought conditions in some regions. These storms also brought cooler temperatures and record snowfalls. As winter continues, attention will be on the snowpack in the Upper Colorado River Basin (UCRB) which provides about 70 percent of the river’s yearly flow; presently, the snow water equivalent in the UCRB is slightly less than the historical average.