Home » December 2011 Southwest Climate Outlook
Published December 20, 2011
Photo of snowy Arizona and New Mexico mountains

Source: Walter Freeman

Winter storms often blanket Arizona and New Mexico mountains with snow. In late November and early December, several storms dumped copious precipitation across the Southwest.

December 2011 Climate Summary

Drought-Drought conditions in Arizona and New Mexico have improved slightly as a result of several early winter storms.  Drought conditions remain widespread, however, due to significant precipitation deficits that have accumulated since the start of last winter.

Temperature-Temperatures have been colder than average in the last 30 days, but near average since the water year began on October 1.

Precipitation-Several winter storms tapped subtropical moisture and moved across Southern California and into Arizona and New Mexico in the past 30 days. As a result, many areas have received more than 150 percent of average rain and snow.

ENSO-Weak to moderate La Niña conditions persist in the tropical Pacific Ocean. Forecasts suggest the event will peak in January or February, with half of the models suggesting it will increase to moderate intensity.

Climate Forecasts-Seasonal precipitation outlooks call for drier-than-average conditions through April in New Mexico and Arizona, with southern regions drier than northern areas. Temperature outlooks call for increased odds of warmer-than-average conditions in New Mexico in the next three months.

The Bottom Line-A weak to moderate La Niña event remains entrenched in the tropical Pacific Ocean and continues to influence below-average precipitation outlooks for the winter. However, several wet and cold early winter storms moved through the region, dumping rain and snow in the Southwest that improved drought conditions in some areas. These storms tapped tropical moisture and chilly polar air, creating ripe conditions for snow to fall at mid-elevations. However, these storms missed the southeast corner of New Mexico, where precipitation in the last month has been below 75 percent of average. Exceptional and extreme drought continue to grip this region. The atmospheric circulation that ferried several early winter storms into the Southwest is somewhat abnormal for a La Niña, which often pushes storms north of the region this time of year. However, weak La Niña events tend to be wetter than moderate or strong events. There is uncertainty about how long and how strong this La Niña will be, but forecasts suggest at least a weak event will persist through the winter.

News Flash: Human actions play a role in extreme events

It’s been called the year of billion dollar disasters. In 2011, extreme drought, heat waves, floods, and wildfires have contributed to a record 12 weather and climate catastrophes, each of which caused more than $1 billion in damages, according to the National Oceanic and Atmospheric Administration. While researchers caution against linking a single event to human-caused climate change, a recent international report states human actions collectively are indeed increasing the intensity and frequency of some extreme events.

On November 18 the Intergovernmental Panel on Climate Change (IPCC) released its Summary for Policymakers, a condensed version of a special report on climate extremes. Publication of the panel’s full report, written by 220 climate experts from 62 countries, is expected in February 2012.
Through activities that increase heat-trapping gases in the atmosphere, the report states, human actions have contributed to raising the lowest and highest daily temperatures and have caused extreme precipitation to become more intense in some regions.  Although the extent of damage caused by disasters has been mounting, the report attributes that trend to people increasingly putting themselves and their property in harm’s way.

Read the summary report at: http://www.ipcc-wg2.gov/SREX/