Weather and Wind charts validity period
Route specific wind charts and vertical cross sections are generated on the basis of WAFS (World Area
Forecast System under ICAO) upper-air forecasts in GRIB2 format.
The WAFCs London and Washington GRIB2 products contain forecasts of global data:
- upper wind
- upper-air temperature
- upper-air humidity
- direction, speed, and height of maximum wind
- tropopause height and temperature
- geopotential height above ground level of standard WAFS flight levels
The WAFS digital grid point data is based on a grid defined as a 1.25° x 1.25° latitude/longitude regular grid.
Datasets contain global data for several standard flight levels. One data set includes forecasts valid for 06,
09, 12, 15, 18, 21, 24, 27, 30, 33 and 36 hours ahead from a time of observation data on which a forecast is
based.
Source Data Availability
| Model Run Time = Forecast Base Time = Weather Observation Time (T) | Dataset valid up to (T+36 hours) | Data available at AIR SUPPORT servers |
| 00:00 | 12:00 next day | 04:00-04:30 |
| 06:00 | 18:00 next day | 10:00-10:30 |
| 12:00 | 00:00 Midnight of the following day | 16:00-16:30 |
| 18:00 | 06:00 in 2 days | 22:00-22:30 |
Route-specific charts are generated on-the-fly and updated with new source data as soon as the data is available on the AIR SUPPORT servers.
Calculation of Values Displayed on Route Specific Wind Chart and Cross Section Graph
The wind chart area is defined by the calculation algorithm so that the planned route is placed in the middle of the chart. The route data is generated by the PPS program and is saved into the database upon upload of the flight to CrewBriefing.
Approximately 14 waypoints are selected for the data to be smoothly displayed on the vertical cross section. If the number of the waypoints is too high, or some waypoints are too close to each other, some of them are skipped so that the symbols do not overlap each other. In the case of a long route with few waypoints or if some waypoints are too far from each other, some “artificial” waypoints are added (e.g. “81NM TO LARBU”) to cover the entire route distance.
The parameter values displayed on the chart are spatially interpolated between the source data available for the standard grid points.
All the values on the level chart are temporally interpolated for the chart time between two sequential forecasts. Ex., if a chart time is 01:25, the parameter values are interpolated between 00:00 forecast data and 03:00 forecast data.
The values displayed on the vertical cross section are interpolated as described above, but unlike the level chart interpolation, the values for each waypoint are interpolated for the waypoint time. Ex., if a waipoint1 time is 01:25, the parameter values are interpolated between 00:00 forecast data and 03:00 forecast data; for a waypoint5 time 03:55 the parameter values are interpolated between 03:00 and 06:00 forecast data.