Storms announce themselves in two ways long before you see them. The first is barometric pressure, which falls — and the speed of the fall matters more than the value it reaches. The second is radio: every lightning strike radiates a burst of radio energy that travels far beyond the range at which you can hear thunder, and that burst is what a lightning detector listens for.
This section brings together the instruments that give advance warning of severe weather: pressure-based storm alerting, dedicated strike detection, and the weather stations that combine rapid-pressure-change alarms with wind gust monitoring. If you manage an outdoor site, a sports ground, a marina, livestock or a work crew, this is the element that has safety consequences.
How lightning detection works
A lightning discharge is an enormous, very short electrical event, and it radiates radio energy across a wide spectrum with most of the power at low frequencies — a few kilohertz up to a few hundred. These emissions are known as sferics, and at low frequencies they travel hundreds of kilometres by following the curve of the earth between the ground and the ionosphere.
A detector picks up that burst on an antenna and estimates range from the strength and shape of the received signal, because a distant strike arrives weaker and with its high frequencies stripped out. Personal detectors report range in broad bands — typically zero to eight, eight to twenty, twenty to forty and forty-plus kilometres — and sound an alarm when strikes appear in the closest band. Long-range professional systems add a direction-finding antenna so strikes can be plotted on a map, and count strike rate over time, which is the single best indicator of whether a cell is building or dying.
The important limitation to understand: a detector tells you a storm is electrically active and roughly how far away, not where it will go next. It buys you time, which is exactly what the well-known thirty-thirty rule needs — if thunder follows the flash within thirty seconds, take shelter, and stay there for thirty minutes after the last one.
Pressure as a storm indicator
Every barometer is a storm warning instrument if you read the trend rather than the number. A fall of 1 to 2 hectopascals per hour signals a deepening system and strengthening wind. A fall of more than 3 hectopascals in three hours is the classic threshold for a rapidly deepening low, and on many electronic stations it is what triggers the storm alarm. What you are watching is the rate of change, so a station that displays a pressure trend arrow or a three-hour graph is worth far more than one showing a single figure.
Wind gusts and squalls
The damaging part of a storm is usually the gust, not the mean wind. A squall line can lift wind speed from calm to fifty knots in under a minute, and any station used for site safety should record and alarm on peak gust rather than averaged speed. Gust thresholds are the trigger most commonly used to close a crane, stop a lift, strike a marquee or clear a pitch.
Detection systems we supply
We stock personal and professional detection. SkyScan produces handheld personal detectors that alarm on strike range, and the supporting mounts, adaptors and power supplies are in the SkyScan Lightning Detectors range. Boltek makes long-range PC-connected systems — the LD-250 and LD-350 — that detect strikes at several hundred kilometres and plot them, with directional Yagi and dipole aerials available; those are in Boltek Lightning Detectors and the combined range is in Lightning Detectors. Because detection systems are specified against site and range requirements rather than bought off a shelf, please call 01243 558280 to discuss configuration and current availability.
Weather stations with storm alerting
If you want pressure-based warning and gust alarms rather than strike detection, several complete stations do the job well. The Bresser Wi-Fi 4CAST MD pushes alerts and holds a pressure history, the Bresser Clearview 7-in-1 WiFi Weather Station and ACCUR8 DWS7100 7-in-1 WiFi Weather Station record gusts and pressure trend with app access, and the Technoline WS 1700 Complete Weather Station is a straightforward console-based option. Where the data has to be defensible, the Davis Wireless Vantage Pro2 with a fan-aspirated shield logs gust and pressure at high resolution and supports configurable alarms.
Related measurements
Pressure instruments are in Digital Barometers and the wider Weather Forecast section. Gust and direction monitoring is in Wind. Complete monitoring systems are in Weather Stations and Professional Weather Stations, logging and mapping applications are in Weather Software, and the full element index is under Elements.