Boltek EFM-100 v.2 - Manual (Page 37)

C H A P T E R 4 - O P E R A T I O N
31
Interpreting the Data Display
Often the first indication of an approaching thundercloud is a positive field reading followed by a
field reversal to a negative field as the cloud moves overhead
Figure 26: Approaching Thundercloud
Figure 27: Increasing Field due to Approaching Thundercloud