Boltek StormTracker PCI - How it works

NH Weather Data's lightning detection center is powered by a Boltek StormTracker PCI. StormTracker works by detecting the radio signals produced by lightning. These are the same signals you can hear as static on an AM radio during a thunderstorm.

Boltek antenna

StormTracker's antenna is a small black box (3"x2"x1-1/2") which may be mounted indoors (in a wood framed house for example) or outdoors. It consists of a crossed loop magnetic field sensor and electric field sensor. The antenna is typically mounted ten to twenty feet above the ground, away from large metal objects and sources of electrical noise such as televisions and computer monitors.

The antenna is very sensitive to electro-magnetic interference. The key factor in reducing interference is to mount the antenna well away from potential noise sources. Apart from this, the detector will only record a signal when it detects an abrupt change in the electric field. If the antenna is mounted correctly, this will only occur for lightning strokes.

Boltek PCI card

The antenna is connected to a PC via a Cat5 data cable. This goes into Boltek's special PCI card where the signals are digitized for processing by software.

Our StormTracker antenna is mounted outdoors, inside a custom made 9" long PVC tube enclosure, approximately 35 feet off the ground. It is located at the southern end of the building, well above the roof peak, to minimize interference and enhance reception. In this location, it can detect storms reliably 350 miles or more away.

While the StormTracker can only detect 1 stroke at a time, it can detect up to 3,000 to 3,500 strokes per second. According to Relko Dimitrijevic with Astrogenic Systems, the highest reported stroke rate to date was slightly over 2,100 per minute - recorded in Australia in 2005.



A product of Astrogenic Systems, Nexstorm is a Microsoft Windows 32-bit application for use with the Boltek StormTracker ISA card, PCI card, and LD250 lightning detectors.

NexStorm combines display, analysis, networking and interprocess communication functionality in a way that makes this software package the most versatile lightning display and analysis application available on the market. Without this software, the Boltek StormTracker would be practically useless.

The software determines stroke type at the software level. For each electro-magnetic pulse that occurs (i.e. for each lightning stroke) the software will obtain a signal waveform which is analyzed in real time.

TRAC Report

There are numerous signatures in a waveform that can tell what type of stroke it was. To determine polarity (positive or negative) the software looks at the electric field at various points in the waveform. To determine the type (cloud to ground or cloud to cloud), the software looks at total waveform length, rise times to peak, peak to zero crossing times, etc.

Direction is determined by looking at the magnetic field ratios for each stroke and using basic trigonometry, i.e. crossed loop antenna direction finding principle.

Initial distance is determined by looking at the signal strength. This however is not very reliable because the signal strength of various strokes occuring at the same exact distance will vary a lot depending on released energy. Therefore, in single antenna lightning detection systems, Nexstorm averages each stroke against a cluster of other strokes that are located towards the same direction, and from that derive a distance to the entire storm cell.

Thunderstorm Ranging and Acquisition, or TRAC for short, is a sub-process in NexStorm that contains all the logic behind computing where thunderstorms are located and analyzing their characteristics. TRAC can also produce a text-based report based on its findings to show you details about individual storms. The TRAC related on map identification feature uses TRAC data to display important information about a thunderstorm. When TRAC has detected what it believes to be a structured thunderstorm system, it will start tracking it until the storm dissipates or the tracking could not be maintained for other reasons.

TRAC key  
Storm ID Key:
Dashed Triangle Strike Rate/Min Classification
Green 1-10 Weak
Yellow 11-49 Moderate
Red >50 Severe
J-3226 is a computer assigned identifier.
- or + indicates dominating strike polarity.
10 indicates last recorded strike rate.
^ - v indicates if storm is increasing, steady, or decreasing.

TRAC will periodically generate a report based on current activity. This is called the TRAC report. While a thunderstorm is being tracked it is also being continuously analyzed. You can view the results of the real-time analysis in the TRAC report.



StormVue is a Java applet, integrated as a part of the NexStorm software. Truly unique to Nexstorm, this allows website visitors the ability to view our lightning data in real time. The applet updates every 60 seconds and allows the viewing of either 30 or 60 minutes of strikes at either 180 or 375 mile radius.

Fast Facts:

• If you can see it or hear it, lightning can hit you. Find shelter now.
• Lightning is the No. 2 weather killer in the US (behind floods).
• Every 5 seconds between flash and boom is a mile's distance from you.
• Under ideal conditions lightning can be heard 12 miles away.
• Lightning is really no wider than a few inches.
• All thunderstorms produce lightning.

A special thanks goes out to for the creation of this document and the permission for us to use it on our site