Cloud-to-ground Flashes Research Articles

Three‐dimensional radio images of winter lightning in japan and characteristics of associated charge structure

We conducted lightning observational campaigns using a three‐dimensional (3D) lightning mapper called the Broadband Observation network for Lightning and Thunderstorms (BOLT) and C‐band radar to further understand the distinct characteristics of winter lightning in the coastal area of the Sea of Japan. We succeeded in locating 3D intracloud (IC) flashes, cloud‐to‐ground (CG) flashes, and upward lightning during winter. The basic characteristics of winter lightning, such as leader speeds and charge structure associated with an IC discharge, are similar to summer lightning. A noticeable difference between the winter lightning and the summer lightning is that the altitudes of the source locations associated with winter lightning are substantially lower than those associated with summer lightning. We performed a statistical comparison of winter and summer lightning. This comparison shows that the BOLT source altitude distributions during winter and summer peak at 2.1 and 7.5 km, respectively. Conversely, the distributions of the BOLT temperatures, which are the temperatures corresponding to the BOLT source altitudes, during both winter and summer show similar trends and have large values near −10 °C. These results indicate that a similar charge separation process, likely a noninductive charging mechanism, primarily contributes to thunderstorm electrification during both winter and summer. We show that the horizontal extent of the winter flashes is substantially larger than that of the summer flashes. This result implies that the charge regions in winter thunderstorms cover a wide area and, therefore, produce CG flashes with large charge transfers. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Locating Preliminary Breakdown Pulses in Positive Cloud‐to‐Ground Lightning

AbstractThis paper provides the first concrete evidence that preliminary breakdown (PB) pulses of either polarity in positive cloud‐to‐ground (+CG) lightning are produced by negative leaders. Three‐dimensional location results of PB pulses in 46 +CG flashes are analyzed. The majority (40) of the +CG flashes started with positive PB pulses (+PBPs), the same polarity as the positive return stroke. Location results showed that +PBPs were produced by leaders propagating upward, which were determined to be negative leaders based on PB pulse polarities. Similarly, for the negative PB pulses (−PBPs) found in six +CG flashes, location results showed that they were produced by leaders propagating downward, and we determined that these were also negative leaders. Upward negative leaders producing +PBPs in +CG lightning are very similar to those in intracloud lightning. They usually propagate upward before turning in a horizontal direction. Downward negative leaders producing −PBPs in +CG lightning are more complicated. They usually move back upward after a period of downward propagation. Positive leaders could not be detected, but their possible propagations are analyzed along with possible charge structures for different types of PB pulses. We also demonstrate that PB pulse studies based on single‐site records are potentially unreliable.

A Performance Evaluation of the World Wide Lightning Location Network (WWLLN) over the Tibetan Plateau

AbstractA systematic evaluation of the performance of the World Wide Lightning Location Network (WWLLN) over the Tibetan Plateau is conducted using data from the Cloud-to-Ground Lightning Location System (CGLLS) developed by the State Grid Corporation of China for 2013–15 and lightning data from the satellite-based Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) for 2014–15. The average spatial location separation magnitudes in the midsouthern Tibetan Plateau (MSTP) region between matched WWLLN and CGLLS strokes and over the whole Tibetan Plateau between matched WWLLN and LIS flashes were 9.97 and 10.93 km, respectively. The detection efficiency (DE) of the WWLLN rose markedly with increasing stroke peak current, and the mean stroke peak currents of positive and negative cloud-to-ground (CG) lightning detected by the WWLLN in the MSTP region were 62.43 and −56.74 kA, respectively. The duration, area, and radiance of the LIS flashes that were also detected by the WWLLN were 1.27, 2.65, and 4.38 times those not detected by the WWLLN. The DE of the WWLLN in the MSTP region was 9.37% for CG lightning and 2.58% for total lightning. Over the Tibetan Plateau, the DE of the WWLLN for total lightning was 2.03%. In the MSTP region, the CG flash data made up 71.98% of all WWLLN flash data. Based on the abovementioned results, the ratio of intracloud (IC) lightning to CG lightning in the MSTP region was estimated to be 4.05.

The Intracloud Lightning Fraction in the Contiguous United States

This work addresses the long-term relative occurrence of cloud-to-ground (CG) and intracloud (IC; no attachment to ground) flashes for the contiguous United States (CONUS). It expands upon an earlier analysis by Boccippio et al. who employed 4-yr datasets provided by the U.S. National Lightning Detection Network (NLDN) and the Optical Transient Detector (OTD). Today, the duration of the NLDN historical dataset has more than tripled, and OTD data can be supplemented with data from the Lightning Imaging Sensor (LIS). This work is timely, given the launch of GOES-16, which includes the world’s first geostationary lightning mapper that will observe total lightning (IC and CG) over the Americas and adjacent ocean regions. Findings support earlier results indicating factor-of-10 variations in the IC:CG ratio throughout CONUS, with climatological IC fraction varying between 0.3 and greater than 0.9. The largest values are seen in the Pacific Northwest, central California, and where Colorado borders Kansas and Nebraska. An uncertainty analysis indicates that the large values in the northwest and central California are likely not due to measurement uncertainty. The high IC:CG ratio (>4) throughout much of Texas reported by Boccippio et al. is not supported by this longer-term climatology. There is no clear evidence of differences in IC fraction between land and coastal ocean. Lightning characteristics in six selected large regions show a consistent positive relationship between IC fraction and the percent of positive CG flashes, irrespective of lightning incidence (flash density), dominant season, or diurnal maximum period.

Lightning and Storm Type in Central Alabama

This study assessed the relationship between cloud-to-ground (CG) lightning and storm type on high-lightning days in Central Alabama during 2007 – 2011 with an emphasis on identifying which types of storms produce the most lightning. Five variables were used to classify high-lightning thunderstorms into 4 types. The storm types include: 1) spring linear events with high CG flash rates; 2) summer airmass events with a high percentage of area above 40 dBZ; 3) spring weak events representing several thunderstorm modes and; 4) summer Mesoscale Convective Systems with high flash rates and the highest percentage of areas above 40 dBZ. This research has the potential to aid forecasters in decision making by associating lightning potential with storm type characteristics observed on days with frequent lightning.

Why Flash Type Matters: A Statistical Analysis

AbstractWhile the majority of research only differentiates between intracloud (IC) and cloud‐to‐ground (CG) flashes, there exists a third flash type, known as hybrid flashes. These flashes have extensive IC components as well as return strokes to ground but are misclassified as CG flashes in current flash type analyses due to the presence of a return stroke. In an effort to show that IC, CG, and hybrid flashes should be separately classified, the two‐sample Kolmogorov‐Smirnov (KS) test was applied to the flash sizes, flash initiation, and flash propagation altitudes for each of the three flash types. The KS test statistically showed that IC, CG, and hybrid flashes do not have the same parent distributions and thus should be separately classified. Separate classification of hybrid flashes will lead to improved lightning‐related research, because unambiguously classified hybrid flashes occur on the same order of magnitude as CG flashes for multicellular storms.

Evaluation of ENTLN Performance Characteristics Based on the Ground Truth Natural and Rocket‐Triggered Lightning Data Acquired in Florida

AbstractThe performance characteristics of the Earth Networks Total Lightning Network (ENTLN) were evaluated by using as ground truth natural cloud‐to‐ground (CG) lightning data acquired at the Lightning Observatory in Gainesville (LOG) and rocket‐triggered lightning data obtained at Camp Blanding (CB), Florida, in 2014 and 2015. Two ENTLN processors (data processing algorithms) were evaluated. The old processor (P2014) was put into use in June 2014 and the new one (P2015) has been operational since August 2015. Based on the natural‐CG‐lightning data set (219 flashes containing 608 strokes), the flash detection efficiency (DE), flash classification accuracy (CA), stroke DE, and stroke CA for the new processor were found to be 99%, 97%, 96%, and 91%, respectively, and the corresponding values for the old processor were 99%, 91%, 97%, and 68%. The stroke DE and stroke CA for first strokes are higher than those for subsequent strokes. Based on the rocket‐triggered lightning data set (36 CG flashes containing 175 strokes), the flash DE, flash CA, stroke DE, and stroke CA for the new processor were found to be 100%, 97%, 97%, and 86%, respectively, while the corresponding values for the old processor were 100%, 92%, 97%, and 42%. The median values of location error and absolute peak current estimation error were 215 m and 15% for the new processor, and 205 m and 15% for the old processor. For both natural and triggered CG lightning, strokes with higher peak currents were more likely to be both detected and correctly classified by the ENTLN.

Relationship between cloud‐to‐ground lightning polarity and the space‐time distribution of solid hydrometeors in isolated summer thunderclouds observed by X‐band polarimetric radar

AbstractTo understand the charge distribution in thunderclouds associated with solid hydrometeors, the relationship between cloud‐to‐ground (CG) lightning polarity and the space‐time distribution of solid hydrometeors for isolated summer thunderclouds in Japan is examined using X‐band polarimetric radar. Hydrometeor classification was conducted to examine the space‐time distribution of dry snow, ice crystal, dry graupel (DG), and wet graupel in thunderclouds. Two thunderstorm cases were selected for analysis: 26 July 2010, which generated few positive CG flashes, and 25 August 2010, which generated positive CG flashes in the reflectivity cores. In both cases, negative CG flashes were observed in all reflectivity cores when a large volume of DG was identified above the height of −10°C level. This is consistent with previous studies showing that graupel particles have a negative charge below temperatures of −10°C. Reflectivity cores with positive CG flashes had a large volume of DG up to high altitudes (around or above the −45°C level). Further, reflectivity cores that sustained large DG volumes at high altitudes had a relatively large number of positive CG flashes. The top height of the DG volume reached lower altitudes for reflectivity cores without positive CG flashes compared with those with positive CG flashes. These results suggest that the persistence of graupel particles in reflectivity cores at high altitudes, implying the existence of strong updraft, is a necessary condition for positive CG flashes in summer thunderclouds. This effect would likely be caused by the positively charged graupel particles under high rime accretion rates.

Inglés

In this paper, important features of electric fields produced by cloud-to-ground (CG) lightning flashes in the central region of Colombia are analyzed. This study is the first conducted in the country where more than 100 CG lightning flash signatures are analyzed. The measurements were conducted at Bogota, Colombia between August-September 2016. A total of 138 electric field waveforms obtained from 7 thunderstorms events with an average duration of 2.7 hours were included. The distance of the electric field signatures with respect to the measuring system was in the range between 40 and 249 km. The statistical analysis showed that 38% of the recorded negative CG flashes were single-strokes, which is a high percentage in comparison with other tropical and sub-tropical regions. The maximum multiplicity during the season was 9 strokes per flash and the average duration of the multiple-stroke flashes was 165 ms. In addition, although electric field signatures present a signal-to-noise ratio (SNR) with a medium level, the preliminary breakdown pulse train was identified in 22.8% of the recorded flashes. The minimum and maximum duration of preliminary breakdown for the examined negative flashes were 800 ns and 22 ms, respectively.

Advanced numerical model of lightning development: Application to studying the role of LPCR in determining lightning type

AbstractAn advanced 3‐D numerical model of lightning development is presented. The key features of the model include the probabilistic branching, bidirectional propagation, nonzero internal electric field, simultaneous growth of multiple branches, physical timing, channel decay, and, for the first time, probabilistic propagation field threshold. The new model can be used for computing electrical parameters of individual branches, including conductivity, current, and longitudinal electric field, each as a function of time, in different parts of the discharge tree. For illustrative purposes, the model was applied to studying the occurrence of lightning flashes of different type depending on the cloud charge structure, with emphasis on the lower positive charge region (LPCR). We demonstrated with the new model that the presence of relatively large (excessive) LPCR can prevent the occurrence of negative CG flashes by “blocking” the progression of descending negative leader from reaching ground. The blocking effect of excessive LPCR was found to occur when the vertical component of electric field near the cloud bottom was negative (downward directed). Further, we showed that significant reduction or absence of LPCR can eliminate the possibility of negative CG flashes and lead to normal‐polarity IC flashes instead. The model predicts the polarity‐asymmetry, which suggests that the amount of collected charge depends not only on the number of branches but also on the dynamics of their conductivity (lifetime) and the local cloud charge density.

Electrification life cycle of incipient thunderstorms

AbstractThis work evaluates how clouds evolve to thunderstorms in terms of microphysical characteristics to produce the first intracloud (IC) and cloud‐to‐ground (CG) lightning flashes. Observations of 46 compact isolated thunderstorms during the 2011/2012 spring‐summer in Southeast Brazil with an X‐band polarimetric radar and two‐ and three‐dimensional Lightning Location Systems demonstrated key parameters in a cloud's vertical structure that produce the initial electrification and lightning activity. The majority (98%) of the first CG flashes were preceded (by approximately 6 min) by intracloud (IC) lightning. The most important aspect of the observations going into this paper, which came originally from the visual examination of a large number of thunderstorms, is that an initial positive differential reflectivity (ZDR) (associated with supercooled raindrops) evolved to reduced ZDR (and even negative values) in the cloud layer between 0° and to −15°C before and during the time of the initial lightning, suggesting evolution from supercooled raindrops to frozen particles promoting the formation of conical graupel. An enhanced negative specific differential phase (KDP) (down to −0.5° km−1) in the glaciated layer (above −40°C) was predominantly observed at the time of the first CG flash, indicating that ice crystals, such as plates and columns, were being vertically aligned by a strong electric field. These results demonstrate that the observations of ZDR evolution in the mixed layer and negative KDP in the upper levels of convective cores may provide useful information on thunderstorm vigor and lightning nowcasting.

Expanding on the relationship between continuing current and in‐cloud leader growth

AbstractWhen lightning connects to the ground, there is a large surge of current, called the return stroke, which is occasionally followed by a longer‐lasting steady current, called continuing current (CC). In a previous study of negative cloud‐to‐ground (−CG) flashes, we observed the growth rate of in‐cloud positive leaders in an attempt to identify occurrences of CC. However, there was no observed change in positive leader growth rate during CC of negative CG flashes. In this study, we use the Langmuir Electric Field Array, Lightning Mapping Array, and Flash‐Continuous Broadband Digital Interferometer data to extend the previous study to the growth of the negative leader during positive CG flashes. We have found that in contrast with previous results, negative leader growth during positive CG flashes does show increases in growth rates coincident with CC. Finally, we find that the growth rate magnitudes for positive and negative leaders are typically ∼2–4 km/10 ms and ∼25–40 km/10 ms, respectively. These contrasting results highlight the differences between positive and negative leaders and provide strong evidence as to why −CC and +CC behave differently. Negative leaders inject higher amounts of current and allow the channel to remain conductive throughout the duration of CC. Whereas for positive leaders, the channel becomes nonconductive relatively quickly. It is therefore disconnected from the channel to the ground, and, due to the positive leader's continued growth, an electric potential is built up until a K event is produced that re‐ionizes the channel.

Relationship between thunderstorm electrification and storm kinetics revealed by phased array weather radar

AbstractWe examine 3‐D lightning location data and radar data obtained through multiple radar observation stations, including two X‐band phased array weather radars (PAWRs), in order to understand the relationship between thunderstorm electrification and storm kinetics. In an investigated convective cell, both intracloud (IC) and cloud‐to‐ground (CG) flash rates drastically change within 25 min. First, the IC flash rate shows a steep increase with a peak at 10 min−1, and then, the CG flash rate peaks 7 min afterward. During the increase phase of the IC flash rate, the radar observation indicates that the echo top height and updraft echo volume in the upper level increase. The upper positive charge regions removed by IC flashes are located in or near the updraft region at high altitudes. On the contrary, the IC flash rate decreases when the updraft at high altitudes weakens. The IC flash rate is well correlated with a proxy for updraft volume in 1 min interval comparison. These results indicate that the IC flash rate has a strong connection with updraft at high altitudes. The CG flash rate peaks when precipitation particles, probably involving graupel, from high altitudes arrive at approximately the −10°C isotherm level. We speculate that graupel from high altitudes might contribute to the initiations of CG flashes. We show an abrupt ascent of the upper positive charge region involved in IC flashes. PAWR observation results indicate that the updraft might have contributed to the ascent of the upper positive lightning charge region.

Initial electric field changes of lightning flashes in two thunderstorms

AbstractThe beginning of all 75 lightning flashes in two small thunderstorms was investigated using an array of electric field change (E‐change) meters and an array of VHF sensors with the goal of determining if an initial E‐change (IEC) preceded the initial breakdown (IB) pulses in each flash. IECs were found at the beginning of all 62 flashes in Storm 1 and all 13 flashes in Storm 2. Hence, it is concluded that an IEC is a fundamental part of most or all lightning initiations and that an IEC is needed prior to the first IB pulse in a flash. IEC durations averaged 0.23 ms for cloud‐to‐ground (CG) flashes (range 0.08–0.54 ms) and averaged 2.7 ms for normal intracloud (IC) flashes (range 0.04–9.8 ms). IEC point dipole moments averaged 26 C m for CG flashes (range 4–86 C m) and averaged −140 C m for normal IC flashes (range −8 to −650 C m). IEC current moments averaged 120 kA m for CG flashes (range 41–410 kA m) and averaged −91 kA m for normal IC flashes (range −2 to −630 kA m). E‐change data support the suggestion that weak narrow bipolar event type events initiate some lightning flashes, but 41 of the 75 flashes had no detectable initiating pulse > 0.04 V m−1 range normalized to 100 km. Two flashes had two IECs; the second IEC of each flash initiated a new lightning channel that propagated in a new direction and at a higher altitude than the original development after the first IEC.

Lightning characteristics relative to radar, altitude and temperature for a multicell, MCS and supercell over northern Alabama

Cloud electrification leads to the production of nitrogen oxides (NOx), which has an effect on ozone concentrations. Currently large uncertainties exist regarding the contribution of lightning to the global and local NOx budget, even on a per flash basis. Most lightning NOx (LNOx) models distribute the LNOx at reflectivities (Z)≥20dBZ in the horizontal, while vertically, a Gaussian distribution function with a peak at −15°C is used for cloud-to-ground (CG) flashes and a bimodal distribution function with peaks at −15°C and −45°C is used for inter- and intra-cloud (IC) flashes. This research aims to improve our basic understanding of lightning location relative to radar Z as a function of storm and flash type. Using data from the North Alabama Lightning Mapping Array (NALMA) and the Multi-Radar Multi-Sensor data suite, the results from analyzing a multicell storm, mesoscale convective system and supercell storm showed that 29.7%, 15.9% and 6.9% of all flashes initiated in regions where Z<20dBZ, respectively. The bimodal lightning initiation distribution for IC flashes was also not observed for any of the three storms. In addition, it is shown that when incorporating the propagation of the flash, the percentage of NALMA lightning sources located in regions where Z<20dBZ increases. Finally, when comparing flash types, the results show that Hybrid flashes have consistently larger sizes than IC and CG flashes, while IC and Hybrid flashes tend to have more sources located at Z<20dBZ than CG flashes.

Relationship between lightning activity and vertical airflow characteristics in thunderstorms

Cloud-to-ground (CG) lightning data, wind field data derived from dual-Doppler radars, and radar reflectivity data are combined to investigate the relationships between CG lightning and the parameters associated with vertical airflow. A new method for the identification of thunderstorm cells based on the aggregation of flashes is developed. It is found that approximately 79.1% of CG flashes are located in the region featuring weak vertical velocity at the 0°C level, ranging from −5 to 5ms−1, with the majority in the weak updraft region, especially for negative CG lightning and the CG lightning in the initial stage of thunderstorms. The CG lightning rate is correlated with the volume of updraft for vertical velocities within certain limits. The sum of absolute precipitation ice mass flux in the region from 7 to 11km is more significantly correlated with the CG flash rate, with correlation coefficients of 0.73, 0.71, and 0.74 for the initial, mature, and dissipating stages of thunderstorms, respectively. On average, the updraft in the thunderstorm at the stage when the last CG flash occurs accounts for a much smaller ratio to the whole volume of the thunderstorm than that corresponding to the first CG flash. The maximum updraft and maximum height of the 10 and 20ms−1 updraft speeds are close for the first and last CG flashes, indicating the dependence of the lightning on strength of updraft. It is deduced that layered large-range charges may be more conducive to the generation of CG flashes than charge pockets in the thunderstorm.

Lightning and Rainfall Characteristics in Elevated vs. Surface Based Convection in the Midwest that Produce Heavy Rainfall

There are differences in the character of surface-based and elevated convection, and one type may pose a greater threat to life or property. The lightning and rainfall characteristics of eight elevated and eight surface-based thunderstorm cases that occurred between 2007 and 2010 over the central Continental United States were tested for statistical differences. Only events that produced heavy rain (&gt;50.8 mm·day−1) were investigated. The nonparametric Mann–Whitney test was used to determine if the characteristics of elevated thunderstorm events were significantly different than the surface based events. Observations taken from these cases include: rainfall–lightning ratios (RLR) within the heavy rain area, the extent of the heavy rainfall area, cloud-to-ground (CG) lightning flashes, CG flashes·h−1, positive CG flashes, positive CG flashes·h−1, percentage of positive CG flashes within the heavy rainfall area, and maximum and mean rainfall amounts within the heavy rain area. Results show that elevated convection cases produced more rainfall, total CG lightning flashes, and positive CG lightning flashes than surface based thunderstorms. More available moisture and storm morphology explain these differences, suggesting elevated convection is a greater lightning and heavy rainfall threat than surface based convection.

Characterization of Positive Cloud to Ground Flashes Observed in Indonesia

The characteristics of 77 electric field changes of positive cloud to ground (CG) flashes in the tropics of Indonesia were investigated. It was found that the arithmetic mean (AM) and geometric mean (GM) values for 0%–100% and 10%–90% rise time were 12.7 μs, 11.9 μs and 6.1 μs, 5.8 μs, respectively. The percentages of single, double, and triple strokes of lightning flashes were 83% (64 cases), 16% (12 cases), and 1% (1 case), respectively. The AM and GM of the interstroke intervals and the return stroke (RS) amplitude ratios were 163.9 ms, 0.29, and 13.3 ms, 0.26, respectively. Furthermore, it was also found that 7 (9%) of 77 positive CG flashes had double peak return stroke waveforms with AM and GM values for 0%–100% and 10%–90% rise time of subsequent return strokes that were 6.7 μs, 6.4 μs and 4.1 μs, 4 μs, respectively. We inferred that these double peaks are produced by two ground terminations with a time interval varying from 7 to 560 μs.

A study of National Lightning Detection Network responses to natural lightning based on ground truth data acquired at LOG with emphasis on cloud discharge activity

AbstractThe U.S. National Lightning Detection Network (NLDN) detection efficiency (DE) and classification accuracy (CA) for cloud discharge (IC) activity (identified here by a sequence of non‐return‐stroke‐type electric field pulses not accompanied by channels to ground) were evaluated using optical and electric field data acquired at the LOG (Lightning Observatory in Gainesville), Florida. Our ground truth “IC events” include 26 “isolated IC events” (complete IC flashes), 58 “IC events before first return stroke,” and 69 “IC events after first return stroke.” For the total of 153 IC events, 33% were detected by the NLDN, and the classification accuracy was 86%. For complete IC flashes, the detection efficiency and classification accuracy were 73% and 95%, respectively, and the average number of NLDN‐reported cloud pulses was 2.9 per detected event. For 24 preliminary breakdown pulse trains in CG flashes, the detection efficiency and classification accuracy were 46% and 82%, respectively. We have additionally estimated the DE and CA for return strokes in CG flashes. Irrespective of stroke order and polarity, the DE was 92% (339/367), and the CA was also 92% (312/339). The DEs for negative first and subsequent strokes were 98% and 90%, respectively.

SAFIR-3000 Lightning Statistics over the Beijing Metropolitan Region during 2005–07

AbstractIn this study, the spatiotemporal characteristics of cloud-to-ground (CG) and intracloud (IC) lightning flashes observed by Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR)-3000 over the Beijing metropolitan region (BMR) during 2005–07 were investigated. The results showed the presence of 299 lightning days with 241 688 flashes, most of which were IC lightning flashes. Only 19% of the total flashes were CG lightning flashes; 14% of these CG flashes were positive. Most lightning activity occurred during the summer months (June–August), with a major diurnal peak around 1900 Beijing standard time (BST) and a secondary peak around 2300 BST. Spatial variations in flash density and lightning days both exhibited an obvious southeastwardly increasing pattern, with higher flash densities or more lightning days occurring in the southeastern plains and lower values distributed on the northwestern mountains. The Z ratio (IC/CG lightning flashes) exhibited a similar spatial pattern, but the percentage of positive CG lightning flashes showed an almost opposite pattern. The results also showed significant topographic effects on the spatiotemporal variations in lightning activity. That is, flash counts on the northeastern and southwestern mountains peaked in the afternoon, whereas those on the southeastern plains peaked in the late night to early morning, which could be attributed to the propagation of thunderstorms from the mountains to the plains. The results showed that the SAFIR-3000 lightning data are more useful than CG lightning data alone for forecasting the development and propagation of thunderstorms over the BMR.