Precipitation

Precipitation since the water year began on October 1 has continued to be much drier than average across nearly all of Arizona. New Mexico, on the other hand, has experienced both wetter- and drier-than-average conditions (Figures 2a–b); eastern and southwestern parts of the state have been dry, while southeastern, central, and northwestern New Mexico have been wet. The extreme variability is due to the position of the storm tracks, availability of moisture, and topography. Areas with higher elevations can squeeze moisture out of the storms more effectively than lower elevations, but many storms have had scant moisture this past winter. A few storms that wafted across southern Arizona had surges of warm, moist air from the western equatorial Pacific Ocean. This led to a large rain event in southern Yuma and western Pima counties of about 1 inch on December 13, which produced more than half of the total average annual rainfall in parts of these regions. The moisture source for central and southern New Mexico was the Gulf of Mexico; high pressure set up over Texas, allowing southeasterly winds to carry moisture westward.  

In the past 30 days, precipitation in parts of southeastern New Mexico was 1–2 inches above average, or more than 150 percent above average, while western New Mexico and virtually all of Arizona was bone dry (Figures 2c–d). Most of the dry areas received less than 0.5 inches of rain, with many places receiving less than 0.1 inches. Dry conditions, however, are expected during this time of year—most of Arizona and Southwest New Mexico receive less than 12 percent of their total annual precipitation in the April–June period. Much of the West also was generally dry as a result of a ridge of high pressure that forced most storm systems to track north of Utah and Colorado.