Home » September 2011 Southwest Climate Outlook
Published September 21, 2011
Photo of Monsoon Thunderstorm

Source: Daniel Griffin, Laboratory of Tree-Ring Research, University of Arizona.

A monsoon thunderstorm soaks a small part of the Gila River Valley west of Safford, Arizona, on July 19, 2011. Photograph is taken from the Pinaleño Mountains.

September 2011 Climate Summary

Drought– Monsoon precipitation during the past 30 days provided some drought relief to parts of New Mexico and Arizona, but overall moderate drought or a more severe category persists across most of the region and even expanded and intensified across parts of Arizona. 

Temperature–Record warmth, continues across the Southwest. Temperatures have been 2–4 degrees F above average throughout most of the region.

Precipitation– The monsoon ramped up in mid-September, delivering copious rain to many parts of the Southwest; the monsoon as a whole, however, has delivered below-average precipitation.

ENSO– La Niña is back and is expected to deliver below-average precipitation to much of Arizona and New Mexico through the upcoming fall and winter seasons.

Climate Forecasts–Seasonal climate outlooks call for above-average temperatures through the new year, while below-average rainfall is forecasted for this winter.

The Bottom Line–The monsoon is nearly over and extreme and exceptional drought conditions remain ensconced in the region, particularly in the southeastern corners of Arizona and New Mexico. Widespread and intense monsoon storms flared up for a week in mid-September, but the total amount of rainfall since June 15 has been slightly below average for most of the region. Scant rain in some parts of the Southwest in conjunction with region-wide, warmer-than-average temperatures caused drought to expand and intensify in Arizona. The Southwest likely will continue to experience drier-than-average conditions because a La Niña event officially has returned. There is uncertainty about how long and how strong this La Niña will be, but forecasts suggest at least a weak event will persist through the winter.

 

News Flash: This Winter May Not Be As Dry As the Last

A climatology equivalent of an economic double dip in the Southwest is back-to-back La Niña events. In September, the National Oceanic and Atmospheric Administration (NOAA) made it official: La Niña has returned after a short hiatus, bringing with it the expectation for dry conditions for a second straight winter in most of Arizona and New Mexico. If the past is a window into the future, however, southeast Arizona and southern New Mexico may not be as dry as last winter.

There have been four La Niña events lasting two consecutive winters or more since 1955. The second winter in each of these events delivered less than 75 percent of average rainfall to most of Arizona, with the least amount of rain and snow falling in southern Arizona. In all but one of these events, New Mexico was generally drier than average. This does not bode well for a region already mired in widespread and severe drought. However, in all four events southern New Mexico received up to 1 inch more rain than it did during the winter of 2010-2011, and in three out of the four events southeast Arizona also received up to an inch more. While a sample size of four is insufficient to draw robust conclusions, there is reason to suspect that parts of the Southwest will receive more rain and snow than last winter.