Motion vector field (MVF)
The motion vector field (MVF) describes the general motion of weather in a set of products.
IRIS Focus calculates current motion vectors (MVF) as the first step in nowcasting calculations.
You can check the MVF product to check the direction and velocity of precipitation in the atmosphere and to verify the nowcasting configurations.
Motion vector indicators
In IRIS Focus, motion vector fields are illustrated with wind barb symbols. Motion vectors on the display show the direction from which the weather is moving. Short barbs and pennants on the vectors indicate the speed, similar to wind barbs on wind displays. A circle indicates calm conditions.
| Symbol | Speed (m/s) | Wind speed (knots) |
|---|---|---|
 |
Calm | Calm |
 |
<1.5 | <3 |
 |
2.6 | 5 |
 |
5.1 | 10 |
 |
7.7 | 15 |
 |
10.2 | 20 |
 |
25.7 | 50 |
 |
38.5 | 75 |
IRIS Focus calculates the MVF by passing a configurable number of a radar products through a nowcasting algorithm.
Because MVF generation can take some time, IRIS Focus generates only one MVF product per site. Once this is configured, IRIS Focus generates MVF products automatically when a new product of the configured type arrives from IRIS.
 | You must configure the MVF before you can start using nowcasting. Many users perform the configuration during installation, but it can also be done later. |
After configuration, IRIS Focus generates the MVF automatically when a new product of the configured type arrives from IRIS. MVF products are not calculated for historical input products.