Summary

Description

The Climate Prediction Center (CPC) issues a series of thirteen probabilistic three-month temperature outlooks for the United States. CPC issues the thirteen outlooks each month with lead times from 0.5 months to 12.5 months. For example, in mid-January, CPC will issue Three-Month Temperature Outlooks for February through April, March through May, April through June, and so on into February through April of the following year. A new set of outlooks would then be released in mid-February for March through May, April through June, and so on into March through May of the following year. CPC expresses the outlooks in a 3-category probabilistic format as the chance the mean temperature for the period will be above, below, or near normal. CPC bases its definition of above normal, near normal, and below normal by dividing a thirty year climatology into equally likely thirds comprising 10 cases each. Note that the base period for the thirty year climatology (currently beginning in 1981 and ending in 2010) is updated once per decade. The top 10 (warmest) cases of this thirty year climatology define the above normal category, the bottom 10 (coldest) cases define the below normal category, and the middle 10 cases define the near normal category. CPC indicates the probability of the most likely category with shaded contours and labels the centers of maximum probability with the letters "A" (for Above Normal), "B" (for Below Normal), or "N" (for Near Normal). For areas where a favored category cannot be determined, CPC indicates those areas with an "EC" meaning "Equal Chances". CPC also accompanies the outlook maps with a technical discussion of the meteorological and climatological basis for the outlooks. CPC may include analysis of statistical and numerical models, meteorological and sea-surface temperature patterns, trends and past analogs, and confidence factors in this technical discussion.