Summary

Description

The Climate Prediction Center (CPC) issues a probabilistic one-month temperature outlook for the United States twice a month. CPC issues an initial monthly outlook with a lead time of 0.5 months on the third Thursday of every month. CPC issues an updated version of the monthly outlook with a lead time of 0.0 months on the last day of each month. For example, in mid-January, CPC will issue a One-Month Probabilistic Temperature Outlook for February. An updated version of this outlook (valid for February) would then be issued at the end of January. New outlooks, valid for March, would then be released in mid-February and the end of February, respectively. 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.