RE: NOAA versus the others
This is a great question. I don't know the methods of other companies (sometimes this is not provided to the public), but I do know of one difference that often shows up in presentation/format. You'll note that CPC outlooks are presented in a probabilisitic format. That is, CPC will tell you the percent chance of three different outcomes (the maps show the color of the outcome that earns the highest percent but there are chances assigned to the other 2 categories as well). There are 3 possible outcomes: above, near, or below average (temperature or precipitation). For example, instead of just telling you that there WILL be below average temperatures in a certain part of the country, CPC tells you that there may be a 40% chance of below average temperatures. The reason we do this is because there is large range of possible outcomes and many different prediction models or methods will give you different answers. We feel that we should give you information that is up-front with this uncertainty so that you can make the decision that is best for you. For some people, they will make a decision if there is a 30% chance of below-average temperatures. Others might not make a decision until there is a 70% chance of below average temperatures.
Check out the current North American Multi Model Ensemble model temperature predictions for DJF 2014-15: http://www.cpc.ncep.noaa.gov/products/NMME/current/ustmp2m_Seas1.html . There are a lof of different combinations! Some models predict below-average temperatures over much of the country, but many other models predict above-average temperatures. And there is generally no "one best model." Some models perform better in certain years than other models, so we don't necessarily know which one is going to be best for a certain year. So, we often take all this information (including more than what you see on this webpage) and we build in this uncertainy into our predictions by presenting them as "a percent chance."
Therefore, this year, as you look at our forecast maps, keep in mind that there is a chance for below-average temperatures over the entire country. However, it is just higher in certain areas (the Southeastern U.S.) than say over the West Coast, where the chance of below average temperatures is less than the chance of above average temperatures.
Also, in addition to being clear about the uncertainty in our format, CPC also provide past assessments of our forecasts showing objective scores that tell you how well the forecasts are doing. We recommend you look through this webpage to see these: