Drought

The moderate-to-strong La Niña event that persisted during the 2010–2011 winter led to record low precipitation across the Southwest. This led to rapidly intensifying and expanding drought conditions across much of Arizona and New Mexico that the ensuing mediocre monsoon did not alleviate.  By the beginning of the 2012 water year, the drought was widespread and intense in the Southwest, with extreme or exceptional drought covering more than 30 and 63 percent of Arizona and New Mexico, respectively. Dry conditions persisted through October and November, further helping to entrench drought conditions that covered most of Arizona and New Mexico (Figure 4a). In December an unusually wet weather pattern delivered above-average precipitation in Arizona, despite the formation of a second consecutive La Niña event. New Mexico, however, received less moisture. Drought conditions improved to moderate levels across Arizona by mid-February, but severe to exceptional drought continued to cling to much of New Mexico (Figure 4b).

The  2011–12 La Niña, albeit a weaker event than the one in the preceding winter, brought the return of dry weather to the Southwest between January and April. Very little precipitation fell during this period, leading to the reemergence of severe drought conditions in many parts of Arizona and western New Mexico. By mid-May, some level of drought blanketed all of Arizona and New Mexico, with most areas classified with at least severe drought (Figure 4c). Monsoon precipitation hit the region in late June and early July, slightly earlier than average. By the end of the summer, monsoon precipitation was close to normal for much of Arizona but below average for most of New Mexico. The monsoon helped improve short-term drought conditions in Arizona, but led to the intensification of drought in some parts of New Mexico (Figure 4d). The water year ended with at least moderate drought covering all of Arizona and New Mexico.
 

Click figures to enlarge.