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• The vertical structure of temperature (red) and moisture (dewpoint, green) in tephigram format, and also dewpoint depression (blue).  Shaded bands denote for the ENS the minimum, 25th and 75th percentiles and maximum for each of temperature, dewpoint and dewpoint 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 HRES and a thick dashed line represents the Control (as on meteogram products).
  
  • Dewpoint depressions are first computed from each ENS member output at each level, and then the  spread and median are derived in the same way as for temperatures and dewpoint.  So maximum dewpoint depression shown is not derived from the highest temperature on any ENS member and the lowest dewpoint on any ENS member at that level.
  • Wind arrows from HRES standard level output are shown on the dewpoint 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 depression information itself.
  • Note that whilst the Control and 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.Image RemovedImage Removed

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Fig8.1.12.2A: An example of ecCharts vertical profile output.

Fig8.1.12.2B: Magnified portion of Fig 8.1.12.2A showing the possible overlap between temperatures and dewpoints among the ENS members.  At some levels (here 910hPa 860hPa taken for illustration) some ENS members forecast dewpoints dew points are higher than the temperature forecast by other ENS members.
Note: since the figures on this web page were created the value range used for dewpoint depression was reduced from 0-50C, to 0- The dew point depression is 0C-20C, to enable the user to see moist environments in more detail.

In order to save disk space and reduce plotting time, whilst at the same time retaining the information most pertinent for forecasting tasks, we elected to used The vertical profile uses every model level in the lower troposphere up to about 700mb, and every other level higher up than that . Before is used to plot the vertical profiles.  Before the spread metrics (e.g. 25th and 75th percentiles) are computed the model levels from each ENS member are all set to correspond the same (ensemble mean) pressure values. For typical mean sea level pressure variations seen up to T+120 this is not problematic. 

Hodograph

Horizontal Winds on Pressure levels

• The vertical structure of winds (m/s) is shown by a wind hodograph that uses one line for each ENS 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  A solid line shows HRES/Ensemble control (which can be compared with, and should be identical to, HRES/Ensemble control winds on the dewpoint depression plot). To avoid plot clutter:
  • the HRES/Ensemble Control run is shown in the same way as the main other ENS members, and.
  • the ENS median is not shown separately.

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Fig 8.1.12.3: An example of ENS and HRES winds plotted as hodographs. Depending  Depending on the case, these can be very informative (e.g. the consistency of significant shear among ENS members).

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In principle, CIN, the convective inhibition, can be computed from any model level.  In practice the temperature structure of the forecast atmosphere is scanned in the vertical, working out what CIN is for parcels rising from each level, and then the minimum of the values that correspond to levels in the lowest 350hPa of the atmosphere is stored in MARS (and used in ecCharts etc.).   Conceptually, CIN is always zero or a positive value.  However in practice where the parcel curve (from any of the levels tested) never even reaches the environment curve (i.e. it lies always to the left of it) then CIN is in effect infinite. We cannot store infinite values so instead  Infinite values of CIN is stored as a missing value indicator is stored whenever the (minimum) CIN encountered exceeds a pre-defined very large threshold (e.g. in strong inversions).

CAPE is different in that it is bounded between 0 and some large, non-infinite, value that depends on atmospheric structure.  So CAPE is stored in a different manner that does not include missing values.

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