METEOROLOGIST JEFF HABY
Sounder data is data obtained from the GOES satellites. This data is not as accurate as the weather balloon (radiosonde)
data and data can not be obtained below clouds but the satellite data can fill in gaps of missing
meteorological data and is an additional resource meteorologists can use to assess the instability
and moisture environment.
The following information will explain several of the index values that can
be obtained from a satellite and a link to the current data.
Instability: Instability assesses the potential for convection intensity if thunderstorms occur. The two
most commonly used instability index values are the LI (Lifted Index) and CAPE
(Convective Available Potential Energy). LI's that are negative are
unstable (the more negative the more unstable). CAPE values that are positive are unstable. The
higher the CAPE and more unstable (i.e. 1,500 is more unstable that 400).
0 to -4 Marginal instability
-4 to -7 Large instability
-8 or less Extreme instability
1 - 1,500 Positive
1,500 - 2,500 Large
Moisture: When there is more moisture in the air there is a greater potential for more intense precipitation and
more precipitation. PW (Precipitable Water) is used to assess the amount of moisture in the air. High PW
combined with slow moving precipitation areas that result in high precipitation totals.
10 mm (millimeters) or less = very low moisture content
30 mm to 40 mm = moderate moisture content
50 mm or above = very high moisture content