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Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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1. On Forecast Charts and Data page, click on any Forecast Range.  A menu of available charts appears.
   
2. Select Medium Range and Point Based Products.  A selection of products appears.
3. Select the Meteograms display.
4. Select meteogram type from drop-down menu or display all ensemble diagrams by clicking on square icon.
   
5. Select location by name or Lat/Long.
   

View directly an example of the meteogram sitea meteogram example.

Overview

The ensemble meteogram provides a probabilistic interpretation of the ensemble for specific locations.  It displays the time evolution of the distribution of several meteorological parameters from the ensemble by a box and whisker plot.  All ensemble meteograms have a title section, giving the name (unless overwritten by the user), the true height of the chosen location, and the co-ordinates of the grid point used based on the ensemble resolution.   

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• 15-day medium-range plot at 6hr intervals for:
  • weather (total cloud cover, 10m wind strength, 6hr rainfall total, 2m temperature).
  • waves (significant wave height, mean wave direction, mean wave period, and strength and distribution of direction of the 10m wind).  If no sea grid point nearby, only wind data is plotted from the nearest land grid point and the wave diagrams are empty. 
• 15-day extended-range plot at 24hr intervals for:
  • weather only (mean total cloud cover, 24hr rainfall total, mean strength and distribution of direction of the 10m wind, max and min 2m temperature).
  • weather only (as above) but also showing M-climate.

Note:

• The Ensemble Control Forecast (ex-HRES) values are shown as a blue line on the 10-day ensemble meteogram. 
• The 15-day ensemble meteogram displays the probability distribution for each calendar day from 00UTC to 00UTC.  For forecasts with data time of 12UTC the first and last 12 hours in the forecast period are excluded and only 14 (instead of 15) daily distributions are generated. 

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Fig8.1.4-4: 10-day medium-range meteogram for Athens data time 00UTC 12 May 2017.  Solid blue lines are Ensemble Control Forecast (ex-HRES).  The red numbers above the precipitation panel are the greatest precipitation value reached by any ensemble member.  Ensemble extreme values cannot be ignored as the evolution of every ensemble member is considered to be equally probable.  Note: Forecast temperatures at 00UTC, 06UTC, 12UTC, 18UTC are shown. 15-day meteograms show forecast maximum and minimum temperatures.  UTC is used exclusively in the meteograms. 

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.4-5: 15-day medium-range meteogram for Dublin from ensemble data time 12UTC 22 June 2023.  The displayed values are for the 24hr period each day, with additionally the distribution of 10m wind direction. Note: Forecast maximum and minimum temperatures are shown.  10-day meteograms show forecast temperatures at 00UTC, 06UTC, 12UTC, 18UTC.  UTC is used exclusively in the meteograms.

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.4-6: As Fig8.1.4-5 with the addition of M-climate data.  M-climate data is shown by shaded colours with percentiles similar to the box and whisker scheme.  The temperature box and whisker for 24 June lies confidently above the 99th percentile of the M-climate.  The median wind forecast for 30 June lies above the M-climate values (above the 75th percentile of the M-climate) with the whisker extending above the 99th percentile of the M-climate.  The median precipitation for the 25 June lies between the 50th and 75th percentile.  Note: Forecast maximum and minimum temperatures are shown.  UTC is used exclusively in the meteograms.

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.4-7: Illustration of the relationship between 10day ensemble presentation and 15day presentation (truncated to 10days for ease of comparison).

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.4-8: Illustration of the relationship between 10day ensemble presentation and 15day presentation (truncated to 10days for ease of comparison).

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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• 10m wind speed in the 10-day ensemble meteogram is the instantaneous forecast value in m/s.  Note this is the mean speed, not the diagnosed gust.  In the 15-day ensemble meteogram as it is the 24-hour wind-speed average of ensemble forecast values at 06, 12, 18 and 24UTC.  Note:
  
  • The peaks of the whiskers should not be interpreted as wind gusts.  ensemble Ensemble products related to gusts should be used (e.g. CDF diagrams).
    
    
• 10m wind direction (only shown in the 15-day ensemble meteogram) is the daily distribution of directions obtained by taking each 6-hourly forecast step for the day (50 members x 4 forecast steps at 06-12-18-24UTC) and allocating it to the relevant octant.  The area of an octant is proportional to the probability of that wind direction (i.e. to the proportion of forecasts falling in that octant).  The probability of each octant is shown by shading light (low) to dark (high).  Note:
  • The wind roses shown on the ensemble meteograms cannot be directly compared as each is scaled to the size of the most populated octant. The size of the wind rose does not refer to wind speed.
    
    
• 2m temperature  in the 10- day ensemble meteogram is shown as instantaneous forecast values at 6-hourly intervals.  In the 15-day ensemble meteogram it is shown as daily maximum and minimum temperatures (in °C).  Note:
  • The forecast temperature is adjusted by using a 5.5K/km lapse rate applied across the difference between the station height (as displayed in the title) and the ensemble orography (the relative heights of ensemble and true orography are shown in the top right corner of the meteogram web page.  In some instances, some information is also included in the temperature panel title of the meteogram itself).

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The total cloud cover in the ensemble is mostly 8 oktas, the low and middle levels have small amounts of cloud.  Therefore a brighter sky may be expected than by considering the total cloud cover alone.   However, the vertical profile strongly suggests thick upper cloud layers implying greyer skies which is reasonable ahead of an approaching front.

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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The total cloud cover in the ensemble is mostly 8 oktas, the low and middle levels have no cloud.  The vertical profile strongly suggests only thin upper cloud layers.  Therefore a much brighter sky may be expected than by considering the total cloud cover alone.

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Note: the so-called land-sea mask processing (where the land or sea nature of the source and target points was used to adjust the interpolation weights) used by the old ECMWF interpolation software scheme (called EMOSLIB) is not used by default in the new MIR interpolation package that was introduced early in 2019.

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