2. Select a Source (5 or 10 day)
3. Select a Cycle
4. Select a Model
5. Select a Forecast Hour
6. Select a Field (parameter/level combination, PMSL = Sea Level Pressure, PW = Precipitable Water)
7. Click on one of the "BIAS" buttons.
After the image displays in the
frame, your selections are saved as default. To generate another plot,
just select different value(s) (change to MRF, F024, etc), and click the
ABOUT THESE IMAGES
If you click the BIAS button:
IMPORTANT !!! This is a "grid-to-grid" comparison, i.e. the "observed" data used to verify the forecast is the initial analysis of the model. Therefore in data void areas, the "observed" data is heavily weighted toward the corresponding forecast from the previous model run. The ECMWF data retrieved at WPC is on a 2.5 x 2.5 degree grid, therefore the ECMWF bias plots will appear more subdued compared to high resolution plots such as the AVN/MRF. Further, the UKMET data retrieved at WPC is on a 1 x 1 degree grid through 72 hours, but on a 2.5 x 2.5 degree grid 96 to 120 hours. The lower resolution 96 to 120 hour forecast grids are mapped onto the higher resolution 1 x 1 degree grid (of the 00 hour grid) in order to be processed in this grid to grid fashion. This means that bias signatures will be potentially more subdued at these lower resolutions compared to other model runs verified on a higher resolution grid.
At times, non-NCEP model data does not arrive cleanly to WPC. This results in bias plots having an over abundance of mostly blue or red contours. (These are also identified by looking at the MEAN contours in GREEN to see if those values look correct). If this is the case, it is usually because of the 5 or 10 cycles that went into the statistical calculation, at least one of those cycles had a corrupt or incomplete grid. The manner in which WPC retrieves this data is the culprit and at present is unavoidable. This situation occurs most often with NOGAPS data.
ENSEMBLE PLOTS are labeled
as 12 or 23. What does that mean ??? These are the number of
members in the ensemble and DIRECTLY RELATE TO THE CYCLE IN WHICH
THEY WERE RUN. Plots obtained from the GLOBAL ENSEMBLE (12) imply
that 12 members from the 12Z contributed to the verification, whereas plots
obtained from the GLOBAL ENSEMBLE (23) imply that 23 members
(12 from the 12Z cyc1e and 11 from the previous 00Z cycle ) contributed
to the verification. You can only access these plots by selecting
a cycle of 12Z.
If you click the BIAS
If you click the HELP AND
TO THIS PAGE in 2002