4.4 TEMPO Group
The TEMPO change group is used to indicate temporary fluctuations to the prevailing conditions.
The TEMPO group is used when conditions are expected to:
- Have a high percentage (> 50%) probability of occurrence and,
- Last for 1 hour or less in each instance and,
- Cover less than half of the time period defined in the TEMPO group
Format: The contraction TEMPO is used followed by eight digits (space between TEMPO and the digits). The first four (4) digits represent the day of the month and the beginning time in UTC the temporary conditions are expected to occur. The last four (4) digits represent the day of the month and the ending time in UTC for the temporary conditions. (Note: There is a forward slash that separates the starting and ending day/time groups).
Following the TEMPO group indicator is a forecast of all of the weather elements that you anticipate to temporarily change. Only those elements that you expect to temporarily change are required in the TEMPO group. Any previously forecast element which you don't include in the TEMPO group is understood to remain the same.
However, if a significant reduction in visibility is forecast in the TEMPO group, the significant weather should be included even though it may have already been forecast in the prevailing conditions. If a significant change is expected in the cloud forecast, all cloud layers should be included in the TEMPO group, even though one of the layers is not expected to change from the initial time period.
Examples:
Some other important points when using a TEMPO group:
- The TEMPO group is placed on a new line in the TAF, indented six (6) spaces from the left margin.
- TEMPO groups will not exceed four (4) hours.
- Consecutive TEMPO groups will not be used.
- TEMPO groups will not include forecasts of either significant weather in the vicinity (VC) or non-convective LLWS.
- If the TEMPO condition is expected to last more than one (1) hour, or more than half the TEMPO period of time defined, then you should view the conditions as "prevailing" and use a FM group to forecast them.