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Forecast Verification
Published August 25, 2010

Temperature Verification

 (September 2010–February 2011)
Data Source(s): Forecast Evaluation Tool

For a thorough description of the interpretation of these maps, see the feature article, "Evaluating forecasts with the RPSS," in the April 2009 issue of the Southwest Climate Outlook.

Comparisons of observed temperatures for September–November to forecasts issued in August for the same period suggest that in southern and western Arizona forecasts have been more accurate than an equal chances forecast, while forecast accuracy for all of New Mexico has been similar to an equal chances forecast (Figure 15a). Forecast skill—a measure of the accuracy of the forecast—is highest in the southern and western regions of Arizona. Skill for the two-month lead time forecasts for October–December increases in all of New Mexico and remains more accurate than equal chances in southeastern and northwestern Arizona (Figure 15b). The three-month lead time forecasts have the most accurate forecasts in southern areas of the Southwest (Figure 15c). However, the four-month lead time forecast has been historically less accurate than equal chances in all of the Southwest, suggesting that forecasts for these periods are less likely to occur (Figure 15d). While bluish hues denote more accurate forecasts, caution is advised to users of the seasonal forecasts for regions with reddish colors.

Temperature Verification
Notes:

These maps evaluate the historical performance of the one- to four-month long-lead forecasts made by NOAA’s Climate Prediction Center (CPC). The maps convey the historical accuracy of the CPC forecasts in relation to the reference forecast, which assigns a 33 percent chance to the three CPC categories, “above,” “below,” and “neutral.”  These categories indicate whether conditions are predicted to be similar to the warmest, coolest, or normal temperatures for 1971 to 2000. The maps are generated from the Forecast Evaluation Tool, which was developed by The University of Arizona in partnership with NOAA, NASA, NSF, and the University of California-Irvine.

The maps display the Ranked Probability Skill Score (RPSS). The more the forecasts and actual weather match, the bluer the color. A bluish or reddish RPSS indicates the forecast is more accurate or less accurate, respectively, than assigning a 33 percent chance to each of the three CPC categories.

The RPSS is calculated by comparing all the forecasts made since December 1994 for particular seasons and specified lead times to the actual weather of the season.

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