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Appendix A
Weather Data
Refer to this appendix to learn more about the weather variables that are measured, dis-
played, and logged by your Vantage Pro2 Station. Some weather variables require
optional sensors. See “Optional Sensors & Transmitting Stations” starting on page 2.
Wind
The anemometer measures wind speed and direction, and is part of the Integrated Sen-
sor Suite (ISS). The console calculates a 10-minute average wind speed and 10-minute
dominant wind direction. The 10-minute average wind speed is displayed in the con-
sole ticker whenever wind has been selected on the console. The last six 10-minute
dominant wind directions are included in the compass rose wind display.
Temperature
The ISS houses the outside temperature sensor in a vented and shielded enclosure that
minimizes the solar radiation induced temperature error. The console houses the inside
temperature sensor. Additional temperature sensors are available for wireless stations
and can measure up to eight locations.
Apparent Temperatures
Vantage Pro2 calculates three apparent temperature readings: Wind Chill, Heat Index,
and the Temperature/Humidity/Sun/Wind (THSW) Index. Apparent temperatures use
additional weather data to calculate what a human body perceives the temperature to be
in those conditions.
Wind chill
Wind chill takes into account how the speed of the wind affects our perception of the
air temperature. Our bodies warm the surrounding air molecules by transferring heat
from the skin. If there’s no air movement, this insulating layer of warm air molecules
stays next to the body and offers some protection from cooler air molecules. However,
wind sweeps that warm air surrounding the body away. The faster the wind blows, the
faster heat is carried away and the colder you feel. Wind has a warming effect at higher
temperatures.
Note: Wind chill is not calculated above 92° F (33° C).
Heat Index
The Heat Index uses temperature and the relative humidity to determine how hot the air
actually “feels.” When humidity is low, the apparent temperature will be lower than the
air temperature, since perspiration evaporates rapidly to cool the body. However, when
humidity is high (i.e., the air is more saturated with water vapor) the apparent tempera-
ture “feels” higher than the actual air temperature, because perspiration evaporates
more slowly.