Precipitation

Since the water year began on October 1, conditions across most of the Southwest have been exceptionally dry (Figures 2a–b). The one notable exception has been near the Arizona–California border and the far northeastern corner of New Mexico. However, small amounts of precipitation can cause above-average precipitation in these regions due to the historically low precipitation during the time. Outside of these areas, southern Arizona and western and central New Mexico have received less than 25 percent of their average precipitation for this time of year, and most areas have measured less than 50 percent of average. This is not uncommon for this period, especially if tropical storms emanating in the Pacific Ocean do not waft into the region.

The past 30 days also were very dry, particularly in the western third of Arizona and eastern New Mexico, both of which received less than 5 percent of average precipitation (Figures 2c–d). Only a small part of Gila County in central Arizona had near-average precipitation. In the last month, only one storm passed through the region, but it did not have much moisture to generate significant rainfall across the region.  More low-pressure systems are expected to sweep across the West in the next several weeks. However, after a few months of expecting an El Niño event to develop and deliver wetter-than-average conditions to many parts of the Southwest, the forecast now is for ENSO-neutral conditions to persist through the winter. ENSO-neutral events, on average, deliver slightly below-average rain and snow to many parts of the Southwest. They also have brought both very wet and very dry conditions, which makes projecting winter precipitation difficult.  La Niña events, on the other hand, almost always bring below-average precipitation to the region.