Following the change to the formula used in HadISDH to calculate the wet-bulb temperature (see details on the HadISDH blog) we updated the forumla used for the humidity data files in HadISD for versions v3.3.0.2022f onwards.
It has recently come to our attention that in doing so we introduced a bug into how this updated formula was being called, and so the Twet values for versions v3.3.0.2022f to v3.3.1.202307p were incorrect (an ice bulb vapour pressure was being used in the call to the routine). This has now been corrected in v3.3.1.202308p.
