Meteograms
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Attention: meteograms for the same place can be different, depending on the area and altitude considered for the forecast. p☼int meteograms adjust the temperature to the altitude fo the selected place. AIR meteograms show average temperature for the region. The extension of the area considered depends on the forecast model and may be indicated in the meteogram.
Attention: time axis for meteograms is in local time. The meteogramAIR is shown in UTC time. For the conversion of UTC into local time, see our Hours & Dates page.
Samples – Click on images to enlarge:
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Meteogram components
Temperature charts
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Precipitation charts
The precipitation charts show the amount, type and probability of precipitation. Precipitation amount is shown in mm (which corresponds to liter per square meter) for the respective time period (e.g. 1 hour). Total precipitation amount (blue bars) is the sum of shower (light blue bars) and frontal precipitation (not indicated separately). Precipitation types are rain (no separate symbol), snow (*), and freezing rain (!). Hail is only displayed for special services. If Precipitation falls as snow, the height of the snow cover can be indicated separately - otherwise, multiply the amount of water by the factor 10 to obtain snow cover. Precipitation probability is calculated from the predicted cloud conditions, the frequency of precipitation forecasts in the region and the frequency of precipitation in previous forecasts, and is shown in percent (%). |
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Cloud chart
Cloud charts show the cloud development during the forecast period, from 0 to 14 kilometer altitude above sea level (km asl). Cloud density is shown in grey scale steps (see chart legend). The average altitude of the surrounding area is plotted on the bottom of the chart. In the sample chart (right side), the selected place (Belalp) is on 1985 m asl, whereas the average altitude of the region is 1200 m. On same days (like on the night from Saturday to Sunday), cloud base (lower end of the clouds) may be below the altitude of the location selected. This can mean fog in the lower areas. Under tropical conditions , the cloud altitude can reach 1 to 3 km more than indicated. From the height, density and sequence of the clouds, you can interpret the type of weather expected. A typical cold front starts with low clouds, which build up over time. Thunderstorm weather is characterized by cloudless mornings and rapid cloud development during the day, with dense and high clouds in the afternoon, which may disappear again during the night. After using to the cloud graph for some time, you will find it easy to understand the expected weather patterns. |
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Wind charts
Wind charts show the hourly wind speed and direction during the forecast period. Wind speed is shown in a curve (km/h) for maximum wind speed (wind gusts) during the previous indicated hour. Wind direction is shown by wind barbs indicating the cardinal directions (N, S, E, W) from which the wind is blowing. A wind barb from the North indicates wind blowing from North to South. For more information on wind speeds and definitions, see our Wind page. |
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Wind barbs
| The barb begins with a feather and finishes in a point. The wind blows from the feather towards the point. The number of "feathers" (lines at the end of the barb) represent the speed. |
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Radiation
Radiation "down" is radiation from sky to ground. Radiation "up" is the radiation from the ground to air.
Latent heat is the amount of energy in the form of heat released or absorbed by a chemical substance during a change of state (i.e. solid, liquid, or gas), or a phase transition.
In the atmosphere, when a molecule of water evaporates from the surface of any body of water, energy is transported by the water molecule into a lower temperature air parcel that contains more water vapor than its surroundings. Because energy is needed to overcome the molecular forces of attraction between water particles, the process of transition from a parcel of water to a parcel of vapor requires the input of energy causing a drop in temperature in its surroundings. If the water vapor condenses back to a liquid or solid phase onto a surface, the latent energy absorbed during evaporation is released as sensible heat onto the surface. The large value of the enthalpy of condensation of water vapor is the reason that steam is a far more effective heating medium than boiling water, and is more hazardous. More information is under http://en.wikipedia.org/wiki/Latent_heat.