FORECAST TIME: 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). More information for conversion of UTC in local time can be found under http://www.timeanddate.com//worldclock/.

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 under http://en.wikipedia.org/wiki/Timezone).

FORECAST RANGE: meteoblue forecasts are available from 0 to 14 days ahead. Other forecast ranges are available on request. The forecast range 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 ranges are defined in days:

•   1-day  = 024 hours from initialization.
•   2-days= 048 hours from initialization. 
•   3-days= 072 hours from initialization.
•   4-days= 096 hours from initialization.
•   5-days= 120 hours from initialization.
•   6-days= 144 hours from initialization. 
•   7-days= 168 hours from initialization.
• 14-days= 356 hours from initialization.

For example, a 7-day 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 initialization 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 range begins only a few hours after initialization, due to quality reasons.

FORECAST INTERVALS: meteoblue forecast are calculated in intervals of a few seconds. For display and services, data are 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 INITIALIZATION is the time at which the forecast calculation is started. It is typically 0:00 and 12:00 UTC, if not indicated otherwise. Initialization 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 initialization. The timing of the update depends on the time necessary for calculating a new "model run", and is 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.

SERVICE PERIOD: is the date range for which the forecast is provided to a customer. It has a start and a finishing date (calendar day), and is may be identical with the subscription period.