Two of the new output parameters introduced with cycle 43r1 are called:

These are computed by scanning upwards through model level data, from the lowest model level (10m); and then saving the height (interpolated) at which wet-bulb temperature (Tw) drops to 0 or 1ºC (respectively). There can in principal be n such levels, where 0 ≤ n. The following figure highlights how we deal with different scenarios for Tw=0ºC. For Tw=1ºC simply assume the vertical black lines are profiles of Tw=1ºC.

- For n = 0, h =0m
- For n = 1, h = given level
- For n = 2, h = level at which n = 2
- For n > 2, h = level at which n = 2

Below is an example HRES forecast, for T+0 to T+120, of the height of the zero-degree wet-bulb temperature: