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Forecasts
Published November 23, 2010

Precipitation Outlook

 (December 2010–May 2010)
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 early spring in all of Arizona and western New Mexico (Figures 10a–d). Probabilities for elevated temperatures are more than 40 percent in the southern halves of Arizona and New Mexico for the December–February period (Figure 10a). Probabilities for increased temperatures exceed 50 percent in southern parts of both states during the January–March and February–April periods (Figures 10b–c). In early spring, elevated temperatures are still expected, but odds decrease slightly in both states (Figure 10d). These outlooks are influenced heavily by the strong La Niña event. Chances that Arizona and New Mexico will receive drier-than-average conditions are highest in the January–March and February–April periods because La Niña events are strongest during these periods and the atmosphere has had time to adjust to cooling sea surface temperatures.

Precipitation Outlook
Notes:

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.

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