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Lightning Detection and Satellite Imagery on the Same Page

Lightning detection versus satellite IR and water vapor on one PWS page: ground networks, optical satellite, and GRLevel3 as display, not a sensor.

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The historical title was “Lighting and Sat Images.” The subject was lightning and satellite pictures sharing a station URL, with GRLevel3 radar as a third panel. Lightning is an electrical detection. Infrared and water-vapor images are geostationary radiance. GRLevel3 is a display client for NEXRAD products. Drawing them in one browser window does not make them one instrument. This article is that split. It is not a live lightning map, not a GOES loop, and not the station-sensor article at /weather-lightning.php.

TNET Weather does not rehost lightning feeds, GLM granules, or old GRLevel3 overlays. TNET is not a warning service. For life-safety decisions use the National Weather Service and local emergency authorities.

Historical context

The recovered /lightning.php page mixed navigation to GRLevel3, a local detector label (SWN-Wasp2), infrared, and water vapor. Body copy then described NEXRAD Level III images for metro Phoenix, generated with GRLevel3, updating every few minutes, times in UTC. That layout is a period artifact: hobby sites stacked every dramatic picture under “lightning.” The original loops, “ONLINE” status flags, and PHP image scripts are not restored and are not current weather.

Two modern reading tasks remain. First, lightning versus satellite IR/water vapor as different evidence on the same page—the intent of the old heading. Second, GRLevel3 lightning overlays as display, not as a sensor. Radar product literacy stays on Level III and GRLevel3. Phoenix beam geometry stays on KIWA. A backyard lightning counter as a station observation type is the neighboring weather-lightning URL, rewritten separately.

Three measurements that only look similar in a browser

Ground-based lightning detection

NOAA’s National Severe Storms Laboratory describes U.S. real-time lightning mapping by ground networks that sense radio waves (sferics) from fast currents in lightning channels. A network locates a stroke when multiple stations detect the same burst, typically by time-of-arrival. Cloud-to-ground return strokes usually produce stronger signals than in-cloud pulses. Location accuracy is best inside the network; outside it, misses and larger errors increase.

The National Lightning Detection Network (NLDN) is the canonical NLDN-class example: a commercial ground network (Vaisala) widely used in U.S. operations. Other networks (for example Earth Networks) use the same broad physics—RF detections, point locations, polarity and peak-current estimates for many cloud-to-ground strokes—with their own coverage and efficiency. This article does not rank vendors and does not paste proprietary accuracy claims. The scientific point is the class: radio-frequency, multi-station, stroke- or flash-located in a ground network.

A local detector on a PWS—optical flash sensor, RF dongle, or a named hobby unit such as the historical page’s Wasp-class label—is not NLDN. It reports events at one site, with a range and false-alarm behavior that belong in the station’s configuration notes. A local count is useful as “the backyard sensor clicked.” It is not a regional flash climatology.

Optical lightning from geostationary orbit

The Geostationary Lightning Mapper (GLM) on the GOES-R series is NOAA’s operational example of satellite lightning: a near-infrared optical detector (777.4 nm) of total lightning (in-cloud, cloud-to-cloud, and cloud-to-ground) as optical pulses at cloud top. NESDIS documents GLM on GOES-East and GOES-West. NSSL notes that GLM records brightness, flash area, and flash rate from above and cannot see whether a channel reached ground. Spatial resolution is coarse compared with a ground-network strike point (on the order of 8–14 km, mapped onto the ABI grid in operational displays).

Detection efficiency varies with flash size, height, and daylight; published comparisons (for example Marchand et al., 2019, JGR Atmospheres) treat GLM and ground networks as different physics, not as interchangeable dots. A hobby overlay that plots every GLM event as a cloud-to-ground pin at the pixel center is a misuse.

GLM is also not infrared cloud imagery. ABI water-vapor and IR window channels are scene radiance. GLM is optical lightning. A 2000s PWS “sat” thumbnail was almost always the cloud image, not GLM. Do not backfill GLM into a 2005 GIF.

Infrared and water-vapor satellite (not lightning)

GOES IR shows cloud-top brightness temperature. Water-vapor channels show mid- and upper-level moisture. Those products are explained as satellite—not radar—on GOES-West. They can outline a thunderstorm’s anvil while lightning is occurring somewhere in the storm. They do not detect strokes. Cold tops are not flash counts. A dry slot on water vapor is not “no lightning.”

GRLevel3 overlays are display

Gibson Ridge GRLevel3 is a Level III viewer. It can draw NEXRAD products and, depending on configuration and available feeds, additional layers (warnings, reports, sometimes lightning). Those extra ticks are whatever data the operator pointed the client at, rendered in the same window as reflectivity. The sensor remains the network or the satellite mapper. GRLevel3 did not hear the sferic and did not see the optical pulse.

If a historical TNET panel said “GRLevel3” next to lightning, the honest caption is: Level III radar product from a named WSR-88D, plus a lightning layer from a named source, plus UTC on each. “Generated with GRLevel3” is plotting credit. Collapsing the layer list into one icon is how a visitor concludes the radar measured lightning.

How to put them on one PWS page without lying

  • Separate panels if captions will not fit. A three-row stack (IR, water vapor, lightning) is clearer than a single composite.
  • Name each source. NLDN-class network, local detector, or GLM; ABI band or product; radar site and product code.
  • Match clocks or show both. An 18:12 UTC IR frame under lightning from 17:40 UTC is two historical scenes.
  • Do not animate lightning on a stale satellite still and call it live.
  • Do not color a cloud pixel as struck because a backyard sensor clicked. At most, the sensor’s documented range is a radius of possible association.
  • Units. Flash counts, flash rates, optical energy, and IR brightness temperature do not share an unlabeled axis.
  • Hazards. Lightning kills. The page must say it is unofficial and must send readers to NWS. Do not imply tornado, hail, or flash flood from a lightning tick; those are other warning families (hazards).

A combined PNG is a juxtaposition. A “storm intensity” color bar built from flash rate is derived. If you did not document the derivation, omit the bar.

Modern relevance

Lightning and heavy convection are weather evidence. They are not a strike-by-strike outage log for a dish, and cloud pictures alone are not a speed forecast. TNET groups atmospheric structure among other inputs on evidence families. Independent Horizon work is reviewed conceptually on the Horizon study page without treating that review as a GLM validation or as a claim that clouds necessarily reduce Starlink throughput.

Observed detections, satellite radiance, modelled fields, and derived outlooks stay labeled on how the service works. A dated planning estimate is the Connection Outlook—not a lightning warning.

Current official cloud imagery: NESDIS GOES viewer. Current official radar: radar.weather.gov. GLM instrument notes: NESDIS GLM. This PHP path displays none of those feeds.

Historical observation pages: observations hub.

Sources