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Fig8.1.5.8: 10-day medium-range meteogram for Oslo from HRES/Ensemble Control (blue line) and ENS members (box and whiskers) data time 00UTC 26 June 2023.   The nearest land grid point to Oslo is at 59.93N 10.83E which lies some 5km away from and some 141m higher than Oslo city centre.  This grid point may well be representative of Haugerud on the fringes of Oslo, but temperatures are reduced to near sea level using 6.5K/km lapse rate.

Examples of selection of grid point for meteograms

Example1: A medium sized island.

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• critically assess forecast values in the light of experience regarding differences between previous forecast values and actual observed observations.
• consider if there are wide variations in orography within an area , because then the representativeness of a grid point can be uncertain.  
• consider the effect representativeness of altitude as meteogram temperatures are adjusted higher or lower according to the difference in altitude between the allocated grid point and the location in question.the meteogram in coastal, island or mountainous regions and take into account consequent differences in height between altitude of the grid point and that of the desired town or location.
• consider the structure of the lower atmosphere as IFS temperature adjustments make assumptions of a uniform lapse rate.
• Inspect meteograms for nearby offshore locations which can add useful information for nearby coastal locations.
• observe when the same ENS grid point is be selected by IFS for both inland and coastal locations as meteograms may not indicate correctly the differences between them.  
• note influences of any Influences of any adjacent sea areas may be over- or under-represented by the ENS meteograms.  
• assess the effect of the forecast winds (e.g. if the wind blows from land to sea then the influence of a nearby sea point may not be relevant).
• assess whether a local effect might be relevant (e.g. onset of a sea breeze), or the local prevalence of persistent cloud (e.g.sea fog and low cloud drifting onshore), or the influence of turbulent mixing with stronger winds. consider the representativeness of the meteogram in coastal, island or mountainous regions and take into account consequent differences in altitude between altitude of the grid point and the desired town or location.cloud drifting onshore), or the influence of turbulent mixing with stronger winds. 
• consider the impact of the land-sea mask value(s) at the grid point on the forecast parameter (temperature, wind, etc) on the meteogram.
• note that a sea grid point (defined as a grid point surrounded by >50% water surface) can be over land and have an altitude defined by ENS orography.  ENS sea grid points do not always have an altitude of 0m.
• The the spectral representation of orography in the IFS, can lead to "topographic ripples" over adjacent sea/large lakes, which decay with offshore distance, and which are most prominent where there are steep-sided high mountains nearby.
• note wind speeds cannot be relied upon in mountainous areas as winds are strongly modified by orography and local effects.

ENS should be taken at face value without consideration of the ways the temperature values are derived and the effects of local influences.  It is for the user to assess critically the representativeness of the Meteogram meteogram displayed and to make adjustments in the light of local knowledge and experience.  Disentangling coastal effects from altitude effects can be difficult. 

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