Version 1.0
©Copyright 2011, Ambient LLC. All Rights Reserved.
Page 10
4.5.2
Weather Forecasting and Tendency
Note:
The weather forecast or pressure tendency is based on the rate of change of barometric
pressure. In general, when the pressure increases, the weather improves (sunny to partly cloudy) and
when the pressure decreases, the weather degrades (cloudy to rain). For significant decreases in
barometric pressure, the storm icon will be displayed. If the temperature is below freezing (32 degF),
the snow icon will replace the rainy or stormy icon.
The weather forecast is an estimation or generalization of weather changes in the next 24 to 48 hours,
and varies from location to location. The tendency is simply a tool for projecting weather conditions
and is never to be relied upon as an accurate method to predict the weather.
The barometer updates every 10 minutes. If the barometer increases for three consecutive updates (30
minutes), the up arrow will be displayed (
). If the barometer decreases for three consecutive updates
(30 minutes), the down arrow will be displayed (
). If there is no clear trend in pressure, the arrows
will not be displayed.
4.5.3
Weather Icons
The six weather icons are Sunny, Partly Cloudy, Cloudy, Rainy, Stormy and Snowy, as shown in
Figure 3. If there is no significant change in pressure, the forecast icon will not change.
Sunny
Partly
Cloudy
Cloudy
Rainy
Stormy
Possible
Snow
Possible
Heavy Snow
Figure 3
4.5.4
Wind Icon
If the air pressure decreases less than -3 mmHg within 3 hours, the wind icon will be displayed, as
shown in Figure 4. This rapid decrease in barometric pressure indicates winds are expected.
Figure 4
4.5.5
Pressure threshold setting
The pressure threshold setting is defined in Section
4.2 Set (Program) Mode
The pressure threshold
(the negative or positive rate of change of pressure signifying a change in the weather) can be adjusted
by the user from level 2 to level 4 (default level 2 mbar/hour).
The lower the level pressure threshold setting, the higher sensitivity for weather forecast changes.
Locations that experience frequent changes in air pressure require a higher setting compared to
locations where the air pressure is typically stagnant.
