Visualizing Summertime Lightning Patterns on Colorado Fourteeners

Abstract

In the context of lightning avoidance, this article explores temporal and spatial patterns of cloud-to-ground lightning strikes to Colorado Fourteeners, the popularly summited set of mountains that exceed 4,267 m (14,000 ft). The article describes the Fourteener concept, examines trends in lightning fatalities and injuries, and reviews thunderstorm climatology across the greater Colorado landscape. Fifteen years (1996–2010) of summertime lightning activity at near-summit locations are examined. Three measures characterize lightning activity for fifty-four Fourteeners: (1) overall strikes received, (2) lightning days, and (3) the time of day when lightning first strikes. Maps, histograms, and ranked lists identify trends and anomalies generated from the three measures. Examples of highest potential risks include Pikes Peak for Fourteener, Front Range for mountain range, and the third week of July for time of summer. The results can help avoid lightning when making long-term plans to visit Fourteeners and can heighten awareness when on Fourteeners. In addition to lightning avoidance, the article contributes to mountain geography and related atmospheric, physical, and social sciences.

本文在避开雷击的脉络下, 探讨科罗拉多 “十四山群” (即顶峰超越4,267公尺或是一万四千英呎的高山群) 云地之间闪电的时间与空间模式。本文描绘 “十四山群” 的概念, 探讨雷击死亡事故和灾害的趋势, 并检视横跨大科罗拉多地景的大雷雨气候学。本研究检视了顶峰附近十五年间 (1996–2010) 的夏季闪电活动。五十四座 “十四山群” 闪电活动的三大测量方法特征如下: (1) 受到雷击的全部次数; (2) 闪电的天数;以及 (3) 一天当中首先受到闪电雷击的时间。本研究将从地图、长条统计图以及排序名册, 指认出三大测量方法所产生的趋势和异常现象。最大可能的风险例子包含十四山群的帕克峰 (Pikes Peak), 山势的前脉, 以及夏季七月的第三个礼拜。研究结果可以帮助我们长期规划造访十四山群时避开雷击, 亦可强化在十四山群上时的警觉性。除了避开雷击之外, 本文亦对山岳地理及相关的大气、物理与社会科学做出贡献。

En el contexto de la protección contra rayos, este artículo explora los patrones temporales y espaciales de los impactos de rayos nube-suelo en las Fourteeners [Catorceras] de Colorado, como popularmente se conoce el conjunto de montañas cuyas cumbres exceden los 4.267 m (14.000 pies). El artículo describe el concepto Fourteener, examina las tendencias de incidentes fatales y de personas heridas por rayos y reseña la climatología de tormentas del más amplio paisaje de Colorado. Se examinaron los registros de quince años (1996–2010) sobre ocurrencia de relámpagos en estaciones próximas a las cumbres. Tres medidas caracterizan la caída de rayos en 54 Fourteeners: (1) el conjunto total de caídas de rayos registradas, (2) días con registro de relámpagos, y (3) la hora del día en que cae el primer rayo. Las tendencias y anomalías generadas por estas tres mediciones son identificadas por medio de mapas, histogramas y listados clasificados. Los ejemplos de los riesgos potenciales más altos incluyen el Pico Pikes en el paisaje de los Fourteeners y la Cadena Frontal en el área de la cadena montañosa, y la tercera semana de julio para la época de verano. Los resultados obtenidos pueden ayudar a evitar la exposición a rayos cuando se trate de hacer planes bien anticipados para visitar las Fourteeners, y pueden incrementar el sentido de alerta cuando se esté allí. Además de prevenir los accidentes por rayos, el artículo contribuye a la geografía de montaña y ciencias atmosféricas, físicas y sociales relacionadas.

Key Words:

• Colorado Fourteeners
• hazards
• lightning
• mountain geography
• spatial and temporal variability

关键词:

• 科罗拉多十四山群
• 灾害
• 雷电
• 山岳地理
• 空间与时间变异。

Palabras clave:

• Fourteeners de Colorado
• riesgos
• rayos
• geografía de montaña
• variabilidad espacial y temporal

Notes

The patterns of lightning behavior presented in this article have been smoothed to more clearly see trends. It is possible for lightning to strike any time of year and any time of day. Lightning can strike with or without precipitation and with or without clouds overhead. Mountains, ridges, vegetation, low clouds, and fog easily hide building storm clouds. Wind and mountain streams overpower the sound of thunder. These environmental factors, combined with the rapidly changing nature of mountain weather, are reasons to stay off above treeline and exposed sections of Fourteeners, especially between 11:00 a.m. and 5:00 p.m., during the peak lightning weeks and months of the summer, and when thunderstorms are forecast. Knowledge of the spatial and temporal patterns described in this article combined with common sense, environmental clues, and updated weather forecasts from local news meteorologists and the NWS are the best sources for minimizing risk.

To help locate the Fourteeners discussed in this article on USGS topographic maps, Fourteener summit elevations are based on the National Geodetic Vertical Datum of 1929 (NGVD 29) rather than the updated North American Vertical Datum of 1988 (NAVD 88). NGVD 29 elevations match those found on commonly used USGS 1:24,000 hard-copy and digital raster graphic topographic maps.

Averaging histograms are well suited for visualizing lightning data (Figures 4 and 5). Averaging compensates for inherent sharp spikes as well as periods of quiescence in lightning activity. A seven-day average meshes with weekend trip planning. The averaging technique suffers two limitations, however. First, the first three days of June and the last three days of September are ignored in the histograms because these dates include fewer than seven days of contributing values for computing averages (Figures 4 and 5). Second, in a few cases, fifteen years of data do not yield sufficient data for the averaging method. In this situation, short gaps break the otherwise seamless histogram trend lines (Figure 5).