I have come across such warnings as many airports and as was said previously, the Met Office issue them when appropriate.
Each AIP states when and to who they are issued.
However, they are in my experience issued to operators and handling agents etc because they are mainly of interest to aircraft parked on the ground. Aircraft in the air get TAF and METARS etc to give the appropriate actual and forecast weather.
Perhaps BRI are trying to save on distribution expenses by simply putting it on the ATIS. Do they also send paper copies to the local handling agent/flying club etc?
Regards,
DFC