Boltek Lightning/2000 - Manual (Page 241)

R E A L - T I M E L I G H T N I N G D E T E C T I O N
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A storm cell over a high mountain peak could be the cause of
a higher –CG count (the distance from the peak to the
negative charge is smaller). This may result in a reduced IC
stroke count, and as a result of the excess positive charge
remaining also a higher +CG stroke count.
If there were mountains to the west and a flat plain to the
east, then the character of storms in these two directions most
likely would be different and the interpretation of the
ratios/flash rates would be different.
Each user needs to keep careful records of ratios and flash
rates of the storms in their area and match these with the
weather service’s classification of the storm. In this way the
display of future storms will convey more meaningful
information about the storm’s nature/severity.
Another Stroke Subtype
Other discoveries by researchers have found that some IC
flashes radiate electromagnetic energy (at very high
frequencies, VHF) more intensely than CG strokes and
other IC flashes. This distinct class of IC flash occurs in
more active thunderstorm cells. These are the narrow
positive bipolar pulse and the narrow negative bipolar
pulse (NPBP and NNBP). Together these are called the
compact intracloud discharge (CID).
These flashes are short (1 km in length or less), oriented
vertically and singular. Because of their vertical orientation,
the signals from these flashes allow their angular location to
be more precise than most IC flashes. But their distribution
is variable; they may be clustered around the updraft (most
likely) or spread throughout the volume of the cloud between
the positive and negative charges. In some severe cells the
CID may account for as much as 20 percent of the total IC
flashes. There is some speculation that CIDs may be the
initial trigger for most IC stroke sequences.