Virtual Weather Station User's Guide
-28- 03/07/06
season. The reason for the change was to improve upon the
current WCT Index used by the NWS and the
Meteorological Services of Canada (MSC, the Canadian
equivalent of the NWS), which was based on the 1945
Siple and Passel Index.
The new formula made use of advances in science,
technology, and computer modeling to provide a more
accurate, understandable, and useful for calculating the
dangers from winter winds and freezing temperatures. In
addition, clinical trials have been conducted and the results
of those trials have been used to verify and improve the
accuracy of the new formula.
Standardization of the WCT Index among the
meteorological community is important, so that an accurate
and consistent measure is provided and public safety is
ensured. Our goal was to implement the new wind chill
formula in Canada and the United States during the same
time frame in order to have a consistent WCT Index for
North America.
Specifically, the new WCT index will:
ü use calculated wind speed at an average height of
five feet (typical height of an adult human face)
based on readings from the national standard
height of 33 feet (typical height of an
anemometer);
ü be based on a human face model;
ü incorporate modern heat transfer theory (heat loss
from the body to its surroundings, during cold
and breezy/windy days);
ü lower the calm wind threshold to 3 mph;
ü use a consistent standard for skin tissue
resistance; and
ü assume no impact from the sun (i.e. clear night
sky).
Virtual Weather Station allows you to use the old or new
wind chill models. For more information, please reference
the National Weather Service:
http://205.156.54.206/om/windchill/index.shtml
6.16.7 Use Channel 1 As Outdoor Temperature
Some weather stations (example, Texas Weather
Instruments, Columbia Weather Systems, Davis Vantage
Pro, and Oregon Scientific) exchange Channel 1
Temperature for Outdoor Temperature. In these special
cases, Virtual Weather Station allows you to swap or
interchange these parameters.
Figure 18- Advanced Parameter Settings
6.16.8 Rainfall Settings
Menu Shortcut: Settings uu Rainfall
Some stations calculate the daily and monthly rain.
In the event the daily and monthly rain is not calculated by
the weather station, the daily rain is calculated by
subtracting the minimum daily rain from the maximum
daily rain. To change the daily, monthly or yearly rain, you
must calculate the difference between the daily maximum
and minimum rain, and enter it in the minimum rain field.
The daily rain is stored by Virtual Weather Station as the
difference between the maximum daily rain and the
minimum daily rain, or:
Daily Rain = Maximum Daily Rain - Minimum Daily Rain
The same is true for monthly and yearly rain.
Note that changing the daily rain does not change the
monthly or yearly rain automatically. You must edit the
monthly and yearly rain fields as well.
Some stations are not capable of reporting daily rain, so
Virtual Weather Station must be operating 24-hours per day
to capture the total amount.
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