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Published November 23, 2010
Temperature Verification(December 2010–May 2010)
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 temperature for December–February to forecasts issued in November for the same period suggest that forecasts have not been more accurate than a forecast of equal chances (i.e., 33 percent chance that temperature will be above-, below-, or near-average) in most of Arizona and New Mexico (Figure 13a). Forecast skill—a measure of the accuracy of the forecast—is substantially higher than equal changes only in northwest Arizona for this period. For the January–March period, forecasts have been better than equal chances in southern regions of both states and northwest Arizona (Figure 13b). For the three-month lead times, forecasts issued in November generally have been more accurate in Arizona than in New Mexico (Figures 13c). Forecasts for the March–May period have been more accurate than equal chances in all of the Southwest (Figure 13d). 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.
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.
For more information on the Forecast Evaluation Tool, visit:
For a CLIMAS publication that explains how to use the Forecast Evaluation Tool, 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 Dubious, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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