Hi
I contacted prolific as suggested and they got back to me very quickly telling me the driver was compatible with Mavericks and that they'd be updating their documentation shortly. So I uninstalled my old version and re-installed version 1.5.1.
Unfortunately I see no difference to the functionality

weathercat is able to link to some of the data (internal & external temp, windchill, internal humidity, wind direction, wind speed, rel pressure & precipitation) but other indicators such as dew point, heat index, external humidity as well as the last 18 days of historical data are not being downloaded

Also I see this date in the Weather Station gauges but not in "Today" window which constantly reads "waiting for weather data to become ready" and displays data which is not the same as the data "Weather Station Gauges"
After about 5 mins I get **WS23xx comms has stopped responding. COULD NOT RESET IT! Please reboot WeatherCat.
Thanks for any other pointers you may have
James