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Forecast Verification
Published May 26, 2011

Temperature Verification

 (June 2011–November 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 June–August to forecasts issued in May for the same period suggest that forecasts have been substantially more accurate than a forecast of equal chances (i.e., a 33 percent chance that temperatures will be above, below, or near average) in most of Arizona (Figure 16a). NOAA–Climate Prediction Center (CPC) forecasts for this season are based in part on recent trends in warming for this season. For the July–September period, forecasts have been better than equal chances in all of Arizona but not as good as equal chances in New Mexico (Figure 16b). For the August–October period, forecasts generally have been more accurate in most of Arizona and less accurate than equal chances in New Mexico (Figure 16c). For the four-month lead time, forecasts have been only slightly more accurate than equal chances in southeastern Arizona (Figure 16d). While bluish hues suggest that CPC historical forecasts have been more accurate than equal chances, 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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