Davis Document 07395-281_IM_06316.pdf which is described as the "Vantage Pro2 Weather Envoy Manual For Vantage Pro2, Vantage Pro2 Plus and Vantage Vue Weather Stations".
andApparent Temperatures
The Weather Envoy calculates four apparent temperature readings: wind
chill, heat index, the temperature/humidity/wind index (THW Index), and
the temperature/humidity/solar radiation/wind index (THSW Index).
THSW is mentioned in the Vantage Pro2 Manual but not anywhere else that I can recall.THW (Temperature - Humidity - Wind)
The THW Index uses humidity and temperature to calculate an apparent
temperature like Heat Index, but includes the cooling and heating effects
of wind on our perception of temperature.
THSW (Temperature - Humidity - Solar - Wind)
The THSW Index uses humidity and temperature like for the Heat Index,
but also includes the heating effects of sunshine and the cooling effects of
wind (like wind chill) to calculate an apparent temperature of what it
“feels” like out in the sun. The THSW Index requires a solar radiation
sensor.