http://www.climas.arizona.edu/swco/oct2012/climate-summary

October Climate Summary, from CLIMAS, Climate Assessment for the Southwest, Vol.11 Issue 10, from Oct. 24, 2102


Drought- Drought conditions remain virtually unchanged from one month ago; all of Arizona and New Mexico are classified with at least moderate drought.

Temperature- Temperatures have been above average in nearly the entire Southwest in the last month; the warmest regions in both states have been 2–4 degrees F above average.

Precipitation- Dry conditions reigned during the last month in the Southwest. Southern Arizona and western New Mexico, where the monsoon ended early, have been the driest.

ENSO- A once-budding El Niño event faltered further this past month. While El Niño still has a greater than 50 percent chance of developing, if it does form it will likely be weak and short-lived.

Climate Forecasts- Temperatures will likely be warmer than average in coming months, while precipitation forecasts do not point to any trends one way or another.

Bottom Line- Since the monsoon ended in September, rainfall has been scant across most of the Southwest, notably in southern portions of Arizona and western New Mexico. This is not unexpected as September and October are often dry, and recent dry weather has reinforced the widespread and intense drought in both Arizona and New Mexico. Currently, most of the Southwest is classified with at least moderate drought, and about 31 and 63 percent of Arizona and New Mexico, respectively, are classified with at least severe drought. In the last year, precipitation has also been below average in most of the Southwest and upper Rio Grande and Colorado River basins, which has contributed to an expansion of drought during this period. It is not all bad news, however. Drought in many areas is not as extreme compared to one year ago. Looking forward, a wet winter is needed to help mitigate widespread impacts, which include low reservoir levels across both states. In New Mexico, 10 of 13 reporting reservoirs have storage less than 18 percent of capacity, including Elephant Butte, which now sits at only 5 percent full. Only a few months ago, the prospect of a wet winter was rosy because conditions in the tropical Pacific Ocean favored the development of an El Niño event; El Niños increase chances for wet winter weather in the Southwest. But in the last few months, odds for an El Niño have declined, and the current forecast is that El Niño has a slightly better than 50 percent chance of forming. Even if it does materialize, it is expected to be weak and short-lived and play a minor role in the winter weather. Without a strong El Niño signal, there are equal chances for above- or below-average precipitation during the November–January period. On the other hand, due in part to recent warming trends, temperatures will likely be above average in coming months, which may cause more precipitation to fall as rain rather than snow at mid-elevations this winter.