1. PRODUCTION:

This is a newly map production of NCEP/NWS/NOAA which was created by Yuejian Zhu and Zoltan Toth since November of 2000. The maps will be produced every day around 7:00-8:00 am with up to 15 days leading time.

2. EXAMPLE MAPS:

The example map is shown here for 5-day forecast of relative measure of predictability. The black contour is 500 hPa height from ensemble forecast mean. The shade colors are the relative measure of predictability which based on ensemble members forecast distribution. Each 10% should be approximately equal to the 10% area of the weighted space of whole domain. The reddest color is showing more ensemble members support ensemble mean forecast ( small spread, less uncertainty ), the dark blue color is showing less ensemble members support ensemble mean forecast ( falling on the same climatological bin, large spread, more uncertainty ).

3. CALCULATION:

To construct this measure, first to calculate the ensemble mean at each grid points, by using 10 climatological bin, you will get how many ensemble members support the ensemble mean ( falling on the same bin ). You will get the measure of predictability by normalized, weighted, space ( Northern Hemisphere extra-tropic ) and time ( past 30 day decaying factors ) average from 11 forecast probability ( e.g. 10 forecast members ) categories. The blue numbers are the probability which come from past verification statistics. For example: 76 means 76% approved by analysis based on past statistics.

4. REQUIREMENTS:

Ensemble forecasts at grid point.

Climatological data set (e.g. monthly mean).

Historical evaluation records ( best have past year ).

5. REFERENCES:

Zoltan Toth, Yuejian Zhu and Timothy Marchok, 2001:

``The Use of Ensemble to Identify Forecasts with Small and Large Uncertainty'' Weather Forecasting, 16. 436-477

http://sgi62.wwb.noaa.gov:8080/ens/yzhu/relpred.html