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Published September 23, 2010
Data Source(s): High Plains Regional Climate Center
Precipitation since the water year began on October 1 has been well below normal on the Colorado Plateau, as well as in the southwestern quarter of both Arizona and New Mexico (Figures 2a–b). These areas, along with northeastern New Mexico, have received 50–90 percent of average precipitation. Central and southeastern Arizona and northwestern and east-central New Mexico have received 100–130 percent of average. A few isolated areas also have seen 130–200 percent of average precipitation, including northeastern Arizona, southeastern New Mexico, and the area near the Nevada-California-Arizona border. The spotty nature of the water year precipitation seems a bit unusual in an El Niño year, when winter precipitation tends to be more uniform. This year, however, the moisture source was inconsistent, and the winter storms tended to be localized.
A decrease in storm activity over the past 30 days left most of New Mexico with less than 50 percent of its average rainfall (Figure 2c). The southern half of Arizona has received 50–100 percent of average rainfall, with areas of southeastern Arizona receiving 110–300 percent of average. A large area covering northeast Arizona and northwest New Mexico has received 130–300 percent of average precipitation. For some areas the summer rainfall filled in gaps left by isolated winter storms, but in many cases the dry areas during the winter were also dry areas during the monsoon.Notes:
The water year begins on October 1 and ends on September 30 of the following year. As of October 1, 2009, we are in the 2010 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.
For these and other precipitation maps, visit:
For National Climatic Data Center monthly precipitation and drought reports for Arizona, New Mexico, and the Southwest region, visit:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer