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.
Population growth, demographic trends, and competition over water resources places increasing demands on existing water supplies, which are subject to demand from end-users fluctuating levels related to temperature and precipitation patterns. In the Southwest, an issue that has become a priority concern is the increased frequency of drought from warming temperatures due to climate change, and how that will impact the supply of water in the near future. In order to conserve water, communities in arid and semi-arid climates are increasingly recognizing green infrastructure as a cost-effective approach that conserves water and also manages stormwater. Furthermore, in order for the Southwest to increase its capacity to respond effectively to future changes in climate, the region must begin to integrate innovative solutions that support sustainable development. (Read More)
Precipitation & Temperature: October precipitation was below average to record driest in Arizona, with the driest conditions occurring in the southwestern corner of the state (Fig. 1a). In New Mexico, precipitation was average to above average in the eastern half of the state, and average to below average in the western half (Fig 1a). October temperatures were above average to much-above average across both Arizona and New Mexico (Fig. 1b) except for small regions in the north and in eastern New Mexico. Thus far, November has been mostly dry in the Southwest (Fig. 2), while temperatures have mostly been above average (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 nearly all of Arizona and New Mexico recording much-above average temperatures, including pockets of record-warmest conditions in both states (Fig. 4b).
Snowpack & Water Supply: Snow water equivalent (SWE) is mostly below average across the Southwest, whereas the opposite has occurred in the Pacific Northwest (Fig. 5). Our dry conditions are partially attributable to persistent warm temperatures and relatively dry conditions in October and November. With the emergent weak La Niña event – and its associated warmer and drier conditions in the Southwest – the potential implications for drought and water resource management are something to watch over the winter season.
Drought: The trend of relatively widespread drought conditions in most of Arizona and western New Mexico continued this past month. The southern third of Arizona is mostly classified as D1 (moderate drought) with a small pocket of D2 (severe drought), while the northern two-thirds is mostly classified as D0 (abnormally dry) with pockets of D1. New Mexico is free of drought designation except for the western edge, which is classified as a mix of D0 and D1 (Fig. 6).
ENSO & La Niña: October saw the onset of a La Niña event that is expected to continue through at least winter 2018. However, the current forecast also suggests this will remain a weak La Niña event, for which correlations to below-average winter precipitation in the Southwest are not as evident (see La Niña Tracker on p. 3-4 for more details).
Tropical Storms: The 2017 eastern Pacific tropical storm season is winding down, and as of Nov. 16, 2017, there have been 18 named storms, including nine hurricanes and four major hurricanes – totals that fell within the expected range of the May 25 NOAA seasonal forecast for 14-20 named storms, including 6-11 hurricanes and 3-7 major hurricanes. Notably, while the eastern Pacific basin was active, very little of the mid-to-late season activity (September-October) reached the Southwest this year. In a typical year, the Southwest often sees a few mid-to-late season tropical storms curve back into the region. Those that arrive prior to Sept. 30 can help boost monsoon seasonal totals, while those that arrive after Oct. 1 can jumpstart water-year precipitation.
Precipitation & Temperature Forecast: The three-month outlook for December through February calls for increased chances of below-average precipitation for nearly all of Arizona and New Mexico (Fig. 7, top), and increased chances of above-normal temperatures for the entire southwestern United States (Fig. 7, bottom).
In the Nov 2017 episode of the CLIMAS SW Climate Podcast, Mike Crimmins and Zack Guido sit down to discussion temperature and precipitation in the Southwest over the past month or so, and the discrepancy between Arizona and New Mexico re: precipitation. They also dive into ENSO and the emergent (weak) La Niña conditions, and what this might mean, taking a close look at last year (another weak La NIña) and other weak La NIña events of the past decades. They wrap up with a quick summary of the seasonal outlooks for the Southwest.