Please join us for the first CLIMAS monthly colloquium of 2018 for a three short presentations followed by a panel discussion focused on our evolving understanding of drought in the Southwest.
Note: This event was on Jan 26, 2018 - click on the links below for YouTube videos of the presentations.
December Precipitation & Temperature: December precipitation ranged from average to much-below average across most of Arizona and New Mexico, with record-dry conditions along the western edge of Arizona and in pockets of central and eastern New Mexico (Fig. 1a). December temperatures were above average to record warmest in both states (Fig. 1b), continuing the pattern observed during fall 2017.
Water Year (to-date) and 2017 Precipitation and Temperature: Looking to the water year (Oct 1-present), much of Arizona and New Mexico have been recording below-normal precipitation (Fig. 2) and above-average temperatures (Fig. 3) for the period (for more details see the water year to date summary). Annual precipitation in 2017 ranged from much-below average to average in Arizona, and from below average to much-above average in New Mexico (Fig. 4a), while average annual temperatures were record warm across most of Arizona and New Mexico (Fig. 4b).
Snowpack & Water Supply: Snowpack and snow water equivalent (SWE) are below average across the Southwest (Fig. 5), with most stations in Arizona and New Mexico recording SWE of less than 25 percent of normal. The above-average temperatures and dry conditions that drove this pattern are attributable, at least in part, to the ongoing La Niña event. If warm and dry conditions persist through winter—not uncommon in a La Niña event—this will have implications for drought and water resource management throughout 2018 (see Arizona and New Mexico reservoir volumes).
Drought: Above-average temperatures and below-normal precipitation are reflected in the expanding areas of drought designation in the Jan. 17 U.S. Drought Monitor (Fig. 6), with Arizona and New Mexico documenting increases in extent and intensity of drought since the December outlook. Most of both states was classified as moderate drought (D1), but severe drought (D2) was noted over a large area along the Arizona/New-Mexico border and in a smaller region of eastern New Mexico. Below-average precipitation in the Southwest over the last few months is a primary driver for these designations, but the drought monitor authors also considered the effect of long-term drought in their designations.
ENSO & La Niña: La Niña conditions continued for another month, although the event may have reached its peak intensity. Current forecasts suggest this weak-to-moderate event will last through winter 2018 before weakening this spring. In the Southwest, weak La Niña events tend to produce drier-than-average winters, but moderate events have resulted in more consistently dry conditions over the winter (see La Niña Tracker and DJF La Niña Precip in the SW for details). Given the drier-than-average conditions in the Southwest last fall and so far this winter, the presence of a La Niña influence continues to cause concern in the Southwest in terms of winter precipitation, drought, and water resource management.
Precipitation & Temperature Forecast: The three-month outlook for February through April calls for increased chances of below-average precipitation for all of Arizona and New Mexico (Fig. 7, top), and increased chances of above-average temperatures for the entire southwestern United States (Fig. 7, bottom).
Precipitation & Temperature: November precipitation was below average across most of Arizona, with record-dry conditions in the western third of the state (Fig. 1a). In New Mexico, precipitation was average to much-below average, with small pockets of record-dry conditions in the central part of the state (Fig. 1a). November temperatures broke record highs across nearly all of Arizona and New Mexico (Fig. 1b). Thus far, December has continued the trend of above-average to near-record temperatures and very dry conditions (Fig. 2), although at the time of this writing (Dec. 20), a series of storms had brought welcome precipitation to the Southwest (Fig. 3). Year-to-date precipitation ranges widely from much-below average in southeastern Arizona to much-above average in northeastern New Mexico (Fig. 4a). Year-to-date temperatures have been consistently warmer than average, with most of Arizona and New Mexico recording either much-above average or record-warmest conditions (Fig. 4b).
Snowpack & Water Supply: Snowpack and snow water equivalent (SWE) are below average across the Southwest, California, and the Pacific Northwest, with a mix of above- and below-average conditions in the Intermountain West (Fig. 5). Most of the Southwest has experienced above-average temperatures and below-average precipitation for much of the fall season (Sept-Oct-Nov), which is a primary factor in the below-average snowpack and concerns about water supply for 2017-2018. The ongoing La Niña event – and its associated warmer and drier conditions in the Southwest – has potential implications for drought and water resource management over the winter season (see Arizona and New Mexico reservoir volumes).
Drought: Above-average temperatures and below-normal precipitation are reflected in the expanding areas of drought designation, with both Arizona and New Mexico seeing increases in extent and intensity of drought. On the Dec. 19 U.S. Drought Monitor (Fig. 6), nearly all of Arizona is classified as moderate drought (D1), with a pocket of severe drought (D2) on the U.S.-Mexico border. New Mexico has likewise seen a widespread expansion of drought conditions, with most of the state now classified as abnormally dry (D0) and intensifying to moderate drought (D1) along the western edge. These classifications are primarily the result of below-average precipitation across much of the region over the last few months, but also include the effect of long-term persistent drought.
ENSO & La Niña: After a relatively late start, La Niña has ramped up in terms of observed conditions and projected intensity, and current forecasts suggest a weak-to-moderate La Niña event lasting through winter 2018. Weak La Niña events tend to produce drier-than-average winters, but moderate events have resulted in more consistently dry conditions over the winter season (see La Niña Tracker and DJF La Niña Precip in the SW for details), Thus, this projected increase in strength is worth watching over the next few months to see how the Southwest fares in terms of winter precipitation, drought, and water resource management.
Precipitation & Temperature Forecast: The three-month outlook for January through March calls for increased chances of below-average precipitation for all of Arizona and New Mexico (Fig. 7, top), and increased chances of above-average temperatures for the entire southwestern United States (Fig. 7, bottom).
This issue of the Rio Grande/Bravo Climate Impacts & Outlook is abbreviated due to the holidays. We will resume In January with a full issue, and we wish everyone a safe and happy holiday.
Esta edicion del Rio Grande/Bravo Impactos Climáticos y Perspectivas se ha abreviado debido a las vacaciones. Continuaremos en enero con una edicion completa, y deseamos a todos unas vacaciones seguras y felices.
Forecasts favor above-average temperatures and below-average precipitation for the Rio Grande/Bravo Basin through February, due to weak La Niña conditions in the tropical Pacific.
Los pronósticos favorecen las temperaturas superiores a la media y las precipitaciones inferiores a la media para la cuenca del Río Grande / Bravo hasta febrero, debido a las condiciones débiles de La Niña en el Pacífico tropical.