Southwest Climate Outlook December 2009

December Climate Summary
Drought – Arizona is blanketed in drought conditions. All of the state has abnormally dry conditions or worse, according to the US Drought Monitor. Although a storm in early December brought widespread snow and rain to many parts of Arizona, dry conditions since the summer have heavily influenced the current drought status. In New Mexico, 43 percent of the state has abnormally dry conditions or worse.
Temperature – During the past 30 days, most regions in Arizona and New Mexico have experienced chillier-than-average temperatures. Except for parts of southern Arizona where temperatures have been 0–2 degrees above average, temperatures generally have been 0–4 degrees below average in the region.
Precipitation – In the past 30 days, central and northwestern Arizona and southern New Mexico have received more than 150 percent of average precipitation. However, more storms are needed to make up for a dry beginning to the water year, which began October 1. Since then, most of Arizona has received less than 50 percent of average precipitation and the western half of New Mexico has received less than 90 percent.
ENSO – Sea surface temperatures in the tropical Pacific Ocean warmed in the past month, and the current El Niño event is moderate in strength. It is likely that El Niño will become stronger or remain the same during the next few months, according to the NOAA–Climate Prediction Center. El Niño conditions also will likely persist into the spring.
Snow – Snowpack in Arizona and New Mexico is well above average. In the Verde River Basin in Arizona, the water contained in the snow (snow water equivalent, or SWE) is 276 percent of average. In the six other reporting basins, SWE is more than 115 percent of average. The Upper Rio Grande Basin in New Mexico reports SWE values of 108 percent of average. Most watersheds in Colorado report between 80 and 100 percent of average SWE.
Forecasts – Temperature forecasts issued by the NOAA–Climate Predictions Center for February–March indicate slightly enhanced chances for below-average temperatures in southeastern Arizona and all of New Mexico; the April–June forecast calls for above-average temperatures. Precipitation forecasts through May call for elevated chances for Arizona and New Mexico to experience above-average precipitation.
The Bottom Line – A dry summer and fall has left the Southwest thirsty for winter storms. While copious rain and snow pounded much of Arizona and parts of New Mexico in early December, more storms are needed to improve drought conditions. Fortunately, El Niño events increase the chances for wetter winters, and the current forecast calls for El Niño conditions to persist or strengthen during the next few months.