How To Use CAPE Maps
Nick Olson avatar
Written by Nick Olson
Updated over a week ago
  • Click on CAPE Maps from the left menu bar.

  • By clicking on the forecast resolution, you can view the maps at 50-kilometer resolution for the GFS and ECMWF. The 8-kilometer resolution is only available on the ECMWF model.

  • The higher the resolution, the more accuracy and detail of the forecast.

  • All maps can be zoomed and panned. To zoom in and out, use the plus and minus zoom controls on the map, your mouse wheel, or the trackpad on your laptop. You can also click on the map to get detailed forecast information for that point on the map in the pop-up box. When the CAPE index is zero, the air will be stable and convection is impossible.

  • For CAPE values up to about 1000, the probability of heavy showers increases. The Higher the value the more unstable the air is. A highly unstable atmosphere is when CAPE values are usually in excess of 2500 joules per kilogram which would supply ample energy for strong updrafts and violent thunderstorms should they develop. The CAPE maps can also be used in conjunction with the rain maps. If a frontal band has a noticeable cape value it may be a more severe event.

The values can be interpreted in the following groupings.

0 to 1000 Marginally Unstable
1000 to 2500 Moderately Unstable
2500 to 3500 Very Unstable
3500 + Extremely Unstable

The standard measurement of CAPE is represented as Joules Per Kilogram; however, a high CAPE value like 2500 J/kg is too many digits to have in our PredictWind forecast tables, so we convert it to KJ/kg (2.5).

The forecast CAPE maps still show J/kg.

Click here to learn more about how to use CAPE maps.

Please click here for more information

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