Instructions on using wind, precipitation and temperature forecasts

Helgi Borg 25.2.2008

Keep the following points in mind:

  • Wind, precipitation and temperature (weather element) forecasts are automatic forecasts, created using a computer model.
  • Read the text forecasts instead of relying solely on the automatic, map-based forecasts.
  • If a large discrepancy exists between the automatic forecast and the text forecast, then the text forecast applies.
  • Keep in mind that short-term forecasts are more likely to be accurate than long-term forecasts.
  • By clicking the left or right arrow key on your keyboard, it is possible to change the time-span of the forecast. Similarly, the weather-element forecasts can be browsed by pressing the numeric keys one to four on your keyboard.

Forecast types:

  • Each component of the weather-element forecast can be viewed by pressing the numeric keys one to four on your keyboard.
  • The weather element forecasts displayed on the maps are wind, precipitation and temperature, in addition to a combined forecast containing all three elements.

Temperature forecasts:

  • The map displays the temperature distribution for the country in degrees Celsius (°C) at an altitude of 2 m.
  • The colours represent 2°C temperature intervals.
  • The temperature scale on the image changes according to the temperature range of the forecast.

Wind forecasts:

  • The map displays wind direction and wind speed (in m/s) based on 10-minute averages.
  • Wind direction is denoted by arrows.
  • The wind-speed scale on the image changes in relation to the forecast speed.
  • The lowest wind-speed interval, 0-2 m/s, is yellow; when the speed exceeds 22 m/s the colour turns purple, and when the wind exceeds 28 m/s red colouring is used.
  • Wind direction and wind speed are displayed as a combined vector. The direction of the arrow is indicative of wind direction, and the length of the arrow signifies the strength of the wind.Vindörvar eru sýndar sem vindfjaðrir eða sem vindvigrar.

Precipitation forecasts:

  • The forecast map displays cumulative levels of precipitation over a 1-hour, 3-hour or 6-hour period, depending on the forecast length.
  • The colour scale denotes precipitation rates, from light precipitation of 0.1 mm/hour (0.3 mm/3 hours and 0.5 mm/6 hours) shown in light yellow, up to heavy precipitation of 50 mm/hour (90 mm/3 hours and 200 mm/6 hours) shown in red.
  • Wind barbs are also shown on the maps. The stem of the barb shows the direction of the wind, which blows toward the point of the barb. Wind-speed is symbolized by diagonal lines at the end of the barb; for instance, a short line represents 2.5 m/s, a long line 5 m/s and a triangle represents 25 m/s.
  • Mean sea level pressure is shown in solid lines, the contour interval is 2 hPa.

The sliding bar below the map is used to change the validity time of the forecast

It is possible to change the validity time in many ways:

  • It is possible to click anywhere on the bar.
  • It is possible to click on the days above the bar to view the noon forecast for a specific day.
  • It is possible to click on the time below the bar.
  • It is possible to click on the arrows on either side of the bar to view the previous or the next validity time.

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