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Published February 23, 2011
Precipitation Outlook(March 2011–August 2011)
Data Source(s): NOAA-Climate Prediction Center (CPC)
The NOAA–Climate Prediction Center (CPC) precipitation outlooks suggest drier-than-average conditions for most of the winter and into the spring for all of Arizona and New Mexico (Figures 10a–b). The highest chances for decreased precipitation in Arizona are projected for the Mach–May period, while the highest chances in New Mexico correspond to April–June. Both of these outlooks in part reflect the expectation that the La Niña event will persist through these periods. As the summer progresses into the monsoon season, precipitation outlooks call for equal chances for above-, below-, or near-average conditions (Figures 10c–d). These outlooks largely reflect the lack of forecast skill for this period. As the monsoon season approaches, more accurate forecasts will be available.
These outlooks predict the likelihood (chance) of above-average, average, and below-average precipitation, but not the magnitude of such variation. The numbers on the maps do not refer to inches of precipitation.
The NOAA-CPC outlooks are a 3-category forecast. As a starting point, the 1971–2000 climate record is divided into 3 categories, each with a 33.3 percent chance of occurring (i.e., equal chances, EC). The forecast indicates the likelihood of one of the extremes—above-average (A) or below-average (B)—with a corresponding adjustment to the other extreme category; the “average” category is preserved at 33.3 likelihood, unless the forecast is very strong.
Thus, using the NOAA-CPC precipitation outlook, areas with light green shading display a 33.3–39.9 percent chance of above-average, a 33.3 percent chance of average, and a 26.7–33.3 percent chance of below-average precipitation. A shade darker green indicates a 40.0–50.0 percent chance of above-average, a 33.3 percent chance of average, and a 16.7–26.6 percent chance of below-average precipitation, and so on.
Equal Chances (EC) indicates areas where no forecast skill has been demonstrated or there is no clear climate signal; areas labeled EC suggest an equal likelihood of above-average, average, and below-average conditions, as a “default option” when forecast skill is poor.
For more information on CPC forecasts, visit:
For IRI forecasts, visit:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubois, New Mexico State Climatologist
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