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Published September 26, 2012
Data Source(s): High Plains Regional Climate Center
Since the water year began on October 1, New Mexico and parts of Arizona have been much drier than average (Figures 2a–b). The La Niña circulation pattern, which helped deflect winter storms to the north, affected both states by reducing precipitation. New Mexico also experienced a below-average monsoon as a result of the position of the subtropical high—generally parked over New Mexico—which kept skies clear and brought little moisture to the state. Arizona, on the other hand, benefitted from the high pressure over New Mexico, as the position created southwesterly airflow that brought copious moisture into the state. The southern and eastern counties received average or above-average precipitation (see page 12). Even western Arizona, the driest area in the state, had a very active monsoon, with some intense storms. The vigorous monsoon helped compensate for precipitation deficits seen in much of Mohave County in the northeast and western Pima County in the south.
The last 30 days were a tale of two states. While Arizona received more than 200 percent of average rainfall over large parts of Arizona, reducing precipitation deficits from the dry winter and spring, New Mexico was relatively dry (Figures 2c–d). In Arizona, only a few isolated areas received below-average rainfall. New Mexico, on the other hand, only enjoyed rainfall over the higher elevations in the north and along the western border. The far northeastern counties received less than 50 percent of their average for this time of year.Notes:
The water year begins on October 1 and ends on September 30 of the following year. As of October 1, 2011, we are in the 2012 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.
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.
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