## 2 Materials and Methods  
The observations were conducted in Bonita Spring, Southwest Florida, from 01:00 UTC to 07:00 UTC on 17 April 2023. Figure 1b displays a map of South Florida, the location of Bonita Springs. Figure 1c illustrates a zoomed-in view of Figure 1b, showing the camera's location and its respective field of view. The camera system utilized was an iPhone 13 ProMax (Apple, Naples, FL, USA) in Bonita Spring, Florida. This camera can operate from a rate of 24 to 240 frames per second (fps) with two resolutions, 1920 \(\times\) 1080 pixels and 3840 \(\times\) 2160 pixels. This camera was positioned at coordinates of 26.3\({}^{\circ}\) N and 81.8\({}^{\circ}\) W.  
It is equipped with GPS and timestamping to synchronize with the lightning location system data. The GLM data were utilized to analyze and identify locations of specific discharges captured in the recording times and to view the entire propagation path and the total propagation distance and height. The pixel size of the discharge path length and height were measured on the frame, and the actual distance between the camera location and the lightning location reported by the GLM, corresponding to the discharge path that occurred, was determined. These pixel sizes and the actual distance are applied to equations (see Equations (A1) and (A2) in Appendix A) to determine the actual vertical height of the lightning discharge corresponding to the image. Additionally, the group energy reported by the GLM was used to investigate the intensity of flash luminosity. The GLM is a satellite-based lightning detection system that detects changes in cloud-top illumination and optical energy, specifically within the wavelength range around 777.4 nm, capturing 500 frames per second [8], which corresponds to a 2 ms interval per frame. The GLM detects optical emissions from both cloud lightning and cloud-to-ground lightning flashes [41]. In GLM detection, an event is defined as a pixel on the GLM detecting light brighter than the estimated background brightness during a single 2 ms frame, while groups are clusters of events occurring simultaneously within the  
Figure 1: (**a**) Location of Florida on a map of the United States; (**b**) a map of Southwest Florida showing the location of Bonita Springs (26.3\({}^{\circ}\) N and 81.8\({}^{\circ}\) W). (**c**) Zoomed-in view of the area indicated by the white dot box in (**b**) showing the location of a camera (26.3\({}^{\circ}\) N and 81.8\({}^{\circ}\) W) with the red dot and its respective field of view represented by the light blue triangle. same frame [8; 42]. Flashes are larger clusters of groups within a time window of 330 ms or less and a distance within 16.5 km [8], provided they match the Euclidian Distance criterion [42]. Group energy refers to the combined energy and overall footprint of all the events within the group, and the GLM can detect with very low energy, down to 1 femtojoule (1 f = \(1\times 10^{-15}\) J) [43]. In addition to GLM data, Band 13 of the Advanced Baseline Imager (ABI), clean-IR brightness temperature with a longwave of 10.3 \(\upmu\)m, was utilized. ABI is a radiometer capturing IR wavelengths ranging from 0.47 to 13.3 \(\upmu\)m [44]. The 'clean'-IR feature is characterized by minimal absorption from ambient water vapor and ozone. This allows for a more precise assessment of convective updraft intensity and glaciation rates with a resolution of 2 km per pixel, covering the continental United States with a grid of 1500 by 2500 pixels [44]. The principal mission of this sensor is viewing clouds in the nighttime; the wavelength that the IR sensor is looking at enables this feature of seeing the complexity of cloud structure when visible light from the sun is not present. The sensor is also used for extreme weather prediction during the daytime, such as hurricanes and strong thunderstorms. The combination of data reported by ABI and GLM helps to understand the characteristics of the cloud-tops in areas where lightning flashes occur. Ref.