Annual Mean Absolute Error Charts


In cooperation with the Climate Prediction Center (CPC), the WPC has verification data for its medium-range minimum and maximum temperature forecasts for days 3, 4, and 5. The first full year for which mean absolute error (MAE) statistics are available is 1972. Verification for 1996 or 1997 is not available. The WPC began forecasting for days 6 and 7 in 1998.

The primary guidance used by the WPC through 1995 was the Klein-Lewis forecast that provided departure from normal (DN) values. There were several other forecast strategies that incorporated various weightings of the Klein-Lewis DN forecast (KL) and a 10-day running bias of the KL (E10). These forecast strategies included:

1. KL - E10
2. KL/2
3. (KL-E10)/2
4. KL - (E10/2)
5. 3*(KL-E10)/4

1983 was the first full year that Linear Regression (LR) forecasts were available. These utilized equations different from the Klein-Lewis forecasts, and included a 60-day running bias correction. MOS forecasts were available starting in the early to mid 1990's, with verification statistics starting from 1998.

Description of "WPC -vs- Guidance" Charts

The red line shows the MAE of the WPC forecasts of max or min temperature for day 3, 4, or 5. WPC MAE data is available 1972-1995 and 1998 to present.

The green line indicates the MAE of the forecast against which WPC was offially compared. During 1972-1995 the WPC was scored against the Klein-Lewis forecasts. By 1998 MOS became the standard against which WPC forecasts were compared, and is currently the only guidance available.

The blue line depicts the MAE of the best performing strategy for that year. This plot terminates after 1995. The WPC has full-year MAE data for the following strategies (as described above) and times:

KL 1972-1995
#1 1972-1982, 1984-1995
#2 1972-1982, 1984-1995
#3 1973-1982, 1984-1995
LR 1983-1995