Detecting the storm, and the risk
Most lightning information comes from networks that locate a strike after it has happened, by triangulating the radio pulse it emits. That is good for tracking a storm across a region, and of little use in the ten minutes before the first discharge over your own deck.
A local detector works differently. It senses the quasi-electrostatic field in the air above it — the charge that builds before a discharge occurs — alongside the discharges themselves. That gives two distinct outputs: where the lightning is, and whether conditions overhead have reached the point where a strike is likely. The second is the one that changes what a deck does.
Detection covers intra-cloud, cloud-to-cloud and cloud-to-ground discharges. Cloud-to-cloud activity usually comes first, so a detector that sees it gives warning before anything reaches the sea or the structure.
What matters offshore
- Overhead warning, not just range. A range ring tells you a storm is approaching. An overhead-risk alarm tells you to stop the lift now.
- Direction. A direction finder turns a detection range into a bearing, so a storm can be watched as it approaches rather than simply reported as present.
- Helicopter operations. CAP 437 expects thunderstorm activity to be reported alongside the rest of the helideck weather. A helicopter can also trigger a discharge in a charged cloud that would not have produced one on its own, which is why the charging state matters as much as the strike count.
- False alarms. A detector that cries wolf gets ignored, or switched off. Discriminating real discharges from local electrical noise is what separates a usable instrument from a nuisance.
- Protection is a separate job. Detection tells people to stop; surge arrestors keep the instrumentation alive when a strike lands anyway. We fit surge protection at the sensor junction boxes and at the cabinet transition point as part of a monitoring system — specified alongside detection, not instead of it.
