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A single display comprises the following elements:

Temperature, Dewpoint dew point and Dewpoint dew point Depression on (most) model levels

• The vertical structure of temperature (red) and moisture (dewpointdew point, green) in tephigram format, and also dewpoint dew point depression (blue).  Shaded bands denote for the ensemble the minimum, 25th and 75th percentiles and maximum for each of temperature, dewpoint dew point and dewpoint dew point depression distributions at each level, with the median value shown by a thin solid line.  This display strategy mirrors the use of box-and-whisker plots on meteograms.  A thick solid line represents Ensemble Control Forecast (ex-HRES) (as on meteogram products).
  
  • Dewpoint dew point depressions are first computed from each ensemble member output at each level, and then the spread and median are derived in the same way as for temperatures and dewpointdew point.  So maximum dewpoint dew point depression shown is not derived from the highest temperature on any ensemble member and the lowest dewpoint dew point on any ensemble member at that level.
  • Wind arrows from Ensemble Control Forecast (ex-HRES) standard level output are shown on the dewpoint dew point depression diagram (5m/s per full barb).  This plotting position was chosen for convenience, and not because of any direct or implied relationship with the dewpoint dew point depression information itself.
  • Note that whilst the Ensemble Control Forecast (ex-HRES) traces for each thermal variable all represent plausible solutions, the same cannot be said for the median traces because they will very probably comprise data from different runs at different levels.

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Fig8.1.8-3: Magnified portion of Fig8.1.8-2 showing the possible overlap between temperatures and dewpoints dew points among the ensemble members.  At some levels (here 860hPa taken for illustration) some ensemble members forecast dew points are higher than the temperature forecast by other ensemble members.  The dew point depression is 0C-20C to show moist environments in more detail. 

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• The vertical structure of winds (m/s) is shown by a wind hodograph that uses one line for each ensemble member and one colour for each of a range of levels (warmer colours for low levels and colder ones for upper levels).  Only data from standard pressure levels are shown.  The radial wind speed scale varies to span the value range represented, with certain values (20, 50, 100 m/s) highlighted to aid quick interpretation.  A solid line shows Ensemble Control Forecast (ex-HRES).  This should be identical to the winds on the dewpoint dew point depression plot).
• To avoid plot clutter:
  • the Ensemble Control Forecast (ex-HRES) run is shown in the same way as the other ensemble members.
  • the ensemble median is not shown separately.

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