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Anatomy of a Thunderstorm
c. Electrical discharges occur as the accumulated masses of
separated positive and negative charges attempt to rejoin.
These discharges continue to occur repetitively as long as the
convective wind shear persists. A few of the discharges are
visible as lightning, but most electrical discharges occur within
a cloud or between clouds and are hidden by those clouds.
Only a small percentage of discharges occurs between the
clouds and the ground. Cloud to ground lightning occurs
when the negatively charged lower part of a cloud induces
a positive charge on an object on the ground. The immense
charge separation finally breaks down the insulating air and
a discharge occurs dumping negative charge from the cloud
onto the object and the surrounding ground.
d. All electrical discharges radiate electromagnetic signals in
all directions close to the speed of light. The electromagnetic
signals have unique characteristics and varying rates of
recurrence and signal strength.
Light
Increasing Turbulence Due to Convective Wind Shear
Figure 2-2. Discharge Rate a Function of Wind Shear
Figure 2-2 shows that the rate of electrical discharges detected in
an area is directly related to the amount of convective wind shear
turbulence present. In fact, as convective wind shear increases, the
rate of electrical discharges increases at an increasing rate. This
relationship means that if you find the electrical discharges, you've
found the wind shear.
2-2
Chapter 2 - Storm Mapping Principles
Moderate
Stormscope
Severe
WX-500 User's Guide
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