Figure 9. Precipitation Outlook (November 2009–April 2010)
Source: NOAA-Climate Prediction Center (CPC)

The NOAA–Climate Prediction Center (NOAA–CPC) long-lead precipitation outlooks through April indicate increasing chances for above-average precipitation along the southern tier of the US and increasing chances of below-average precipitation throughout the Pacific Northwest (Figures 9a–d). These outlooks rely heavily on the expected impacts of the current El Niño event, which typically brings wetter winter conditions to the southern part of the US and drier conditions to the Northwest and Ohio and Mississippi valleys.

For Arizona and New Mexico, the forecast through the end of 2009 and into January 2010 indicate equal chances of above-, below-, and near-average precipitation (Figure 9a). The outlook through April for the southern portions of the Southwest shows a slight tilt in the odds toward conditions that are similar to the wettest 10 years of the 1971–2000 observed record.

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 the reliability (i.e., ‘skill’) of the forecast is poor; areas labeled EC suggest an equal likelihood of above-average, average, and below-average conditions, as a “default option” when forecast skill is poor.

More Information:
For more information and the most recent forecast images, visit: http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_
outlooks/color/churchill.html. Please note that this Web site has many graphics and may load slowly on your computer.

For IRI forecasts, visit: http://iri.columbia.edu/climate/forecast/net_asmt/