Versions Compared

Old Version 4

changes.mady.by.user Bob Owens

Saved on

compared with

New Version 5

changes.mady.by.user Bob Owens

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

Output focuses mainly on the week-to-week changes in the weather rather than attempting to give unsupportable detail on individual days.  Output is mostly in the form of anomalies relative to ER-M-climate and is mainly shown as 7-day means for calendar weeks Monday-Sunday.   Specialised products for the extended range also include information on potential tropical cyclone activity and the Madden-Julian Oscillation (MJO) during the coming month.

Availability of Graphical Products

...

On extended range web charts the confidence is "over-stated", because reliability diagrams consistently show that forecasts are over-confident.  Thus where a high probability of a particular type of event is predicted, the "true" chances of that event happening are actually less than the probability that is shown. 

Some broad indications of ensemble performance and predictability in the extended range should be taken into account when considering the extended range output.  Users are strongly encouraged to consult verification information - e.g. monthly forecast reliability diagrams diagrams (for 2m temperature, surface temperature, total precipitation, mean sea level pressure) or monthly forecast relative operating characteristics (ROC) diagrams (for 2m temperature, surface temperature, total precipitation, mean sea level pressure).  An explanation of reliability diagrams and ROC diagrams is given in the annex to this guide).  Users can also reference metrics that describe how skill tends to vary in different scenarios - see General use of Extended Range Output section.

A particular consideration when using the precipitation charts is that the range of colours available for "below average" anomalies (red colours) is constrained by the local climatology in the ER-M-climate.  For example if all ensemble members showed a dry week, the mean (-ve) anomaly could be no larger in magnitude than the mean in the ER-M-climate.  So in some locations the strongest dry signal one can ever see will only be in the first or the second of the red shades.

...