Precipitation

(data through 10/19/11)
Data Source(s): High Plains Regional Climate Center

Precipitation since the water year began on October 1 has been variable, with above-average rainfall in the north and below-average rainfall in the south (Figures 1a–b). Northwestern Arizona and northern New Mexico have received 150–800 percent of average precipitation, while southern Arizona and southern New Mexico have received less than 50 percent. Yuma, La Paz, and Santa Cruz counties in Arizona and Lea, Eddy, Doña Ana and Union counties in New Mexico have been the driest, receiving less than 2 percent of average precipitation.

In the past 30 days, early fall storms have brought rainfall to Southern California but they generally have not moved across Arizona and New Mexico (Figures 2c–d). The exception is in northwestern New Mexico, where the past 30-day precipitation is 100–150 percent of average. In Arizona, eastern Maricopa County has received less than 2 percent of average precipitation in the last month.

Notes:

The water year begins on October 1 and ends on September 30 of the following year. As of October 1, 2010, we are in the 2011 water year. The water year is a more hydrologically sound measure of climate and hydrological activity than is the standard calendar year.

Average refers to the arithmetic mean of annual data from 1971–2000. Percent of average precipitation is calculated by taking the ratio of current to average precipitation and multiplying by 100.

The continuous color maps (Figures 2a, 2c) are derived by taking measurements at individual meteorological stations and mathematically interpolating (estimating) values between known data points. Interpolation procedures can cause aberrant values in data-sparse regions.

The dots in Figures 2b and 2d show data values for individual meteorological stations