meteoblue uses the Gregorian calendar dates . The notations can be:
If not otherwise indicated, the date is calculated for the timezone "Coordinated Universal Time" (UTC). The actual date depends on the timezone considered.
meteoblue uses "Standard time" for which weather information is given. The time is displayed in "hours" and "minutes", for the timezone selected. More information for conversion of UTC in local time can be found here.
Forecast time is the hour for which a forecast is made. They are displayed in local time, or in UTC (Coordinated Universal Time) if no local time is available, if international conventions are used (like for AIR traffic) or if forecasts cover more than one timezone (like on a continental map).
Local forecasts are adjusted to the local time zone using the selected place or location. In some cases, local timezone management and switches of standard to summer time may lead to inaccuracies of +/-1 hour (see also timezone explanation here).
meteoblue forecasts are available from 0 to 14 days ahead. Other forecast periods are available on request. The forecast period is defined by the first forecast day (d01) and last forecast day (dL; or d06, d14). Day of delivery (dD) is either the first forecast day (d01) or the day before (d00). For delivery, meteoblue forecast periods are defined in days:
- 1-day = 024 hours from initialisation.
- 2-days = 048 hours from initialisation.
- 3-days = 072 hours from initialisation.
- 4-days = 096 hours from initialisation.
- 5-days = 120 hours from initialisation.
- 6-days = 144 hours from initialisation.
- 7-days = 168 hours from initialisation.
- 14-days = 356 hours from initialisation.
For example, a 7-days forecast based on 00:00 UTC initialisation will contain data from 00:00 UTC of the first forecast day (d01) to 23:00 UTC of day 7 (d07 = end of d07). Forecast initialisation 12:00 UTC will contain data from 12:00 UTC of the first forecast day (d01) to 12:00 UTC of day 8 (d08). For "daily" data packages, the maximum temperature for the last day (d08) will be missing (value provided is -999) in the dataset from the 12:00 initialisation, because maximum temperature typically occurs after 12:00 UTC. For some datasets, the forecast period begins only a few hours after initialisation, due to quality reasons.
meteoblue forecasts are calculated at intervals of a few seconds. For display and services, data is extracted for each full hour. Shorter or longer time steps are available on request. For display, meteoblue forecast are typically shown by:
- date (calendar day);
- daytime (from sunrise to sunset) or nighttime;
- 6-hourly intervals = day period: morning from 6-12, afternoon 12-18, evening 18-24, night 24-6 o'clock;
- 3-hourly intervals (as displayed);
- hourly: from first hour + number of forecast hours.
Forecast initialisation is the time at which the forecast calculation started. It is typically 0:00 and 12:00 UTC, if not indicated otherwise. Initialisation is based on new updates of weather "assimilation" data, which describe the most recent measured state of the atmosphere over the area of interest.
Forecast update is the time at which the forecast data are updated, which occurs 4-9 hours after initialisation. The timing of the update depends on the time that is necessary for calculating a new "model run", and happens earlier for forecasts with lower resolution and later for higher resolution forecasts. A "late" update may therefore provide a better forecast than an "early" update, if the forecast is made for an area with large differences in topography (mountains) or land surface (lakes, sea shore), where higher resolution leads to substantial improvements in accuracy.
The service period is the date range within which the forecast is provided to a customer. It has a starting and a finishing date (calendar day) and might be identical to the subscription period.