Home » May 2011 Southwest Climate Outlook
Published May 26, 2011
In the Las Cienegas National Conservation Area southeast of Tucson.

In the Las Cienegas National Conservation Area southeast of Tucson, the parched winter has primed grasses and trees for fire. Dry conditions have become a mainstay in many parts of Arizona and New Mexico since November, causing fire activity to be above average, particularly in southern regions of the Southwest. Photo was taken on December 5, 2010.

Source: Benjamin Blonder

May Climate Summary

Drought– Drought conditions have continued to intensify across Arizona and New Mexico during the past 30 days, with exceptional drought expanding across much of southern New Mexico. Extreme and exceptional drought now occupies about 16 and 65 percent of Arizona and New Mexico, respectively.

Temperature– Temperatures are within 2 degrees F of average, with the northern counties of Arizona and New Mexico generally cooler than average and the southern counties generally warmer than average.

Precipitation– The southern halves of Arizona and New Mexico have received less than 2 percent of average precipitation during the last 30 days.

ENSO– Sea-surface temperatures continued to warm this past month across the eastern Pacific and the La Niña event has officially ended. Neutral conditions are expected to persist through the upcoming summer season.

Climate Forecasts– Temperature outlooks call for greater than a 50 percent chance of warmer-than-average conditions in the Southwest through the summer; monsoon precipitation forecasts call for an equal likelihood of near-, above-, and below-average precipitation.

The Bottom Line–A record-setting dry winter in parts of the Southwest has led to widespread and intense drought conditions that are fueling increased fire activity. The next few months are typically dry and forecasts call for warmer-than-average conditions, making parts of the region still vulnerable to wildland fires. To date, nearly 1,000 fires have burned 425,000 acres in Arizona and New Mexico this year. The risk of fire and the effect of other drought impacts likely will continue to mount until the monsoon season begins. While the official monsoon outlook forecasts equal chances for above-, below-, and near-average precipitation, there is reason for optimism. Generally, dry winters are followed by wet summers, although this pattern has not always held true.

Southwestern Trees Hold the History—and Future?—of El Niño

The impact of tropical Pacific Ocean temperatures on the hydrology and climate of the Southwest is profound. On timescales of two to eight years, El Niño and La Niña events, which feed off those ocean temperatures, influence the amount of winter precipitation the region receives. Trees living across the Southwest record these changes in moisture in the width of their rings, providing a history of precipitation going back thousands of years.

Scientists contributing to the Southwest Climate Change Network reviewed a study in the journal Nature Climate Change that used tree rings to reconstruct the strength of past El Niño and La Niña events. The study indicated that during past time periods when the tropical Pacific Ocean was warmer, the strengths of La Niña and El Niño events were stronger. This implies that global warming could intensify the impacts associated with these events in the future, bringing more severe dry winters during la Niña events and more precipitation during El Niños.
Read more about this study and other news and climate-related information at: http://www.southwestclimatechange.org