Kerryn Hawke

Convective storms can cause significant disruption to human activity, danger to life and damage to property and livelihood. Hazards include heavy rain and associated flash flooding, lightning and associated wild fires, hail, strong wind gusts and tornadoes. Convective storms in New Zealand occur, on average, fifteen to twenty days per year in northern and western parts of the country, while on the east coast of the South Island the average is commonly less than five occurrences per year. While thunderstorms are infrequent in New Zealand when compared to countries such as Australia and the USA, associated hazards like lightning still pose a risk to humans and so a better understanding of spatial and temporal patterns of severe convective activity is valuable to assist in decreasing associated risk factors. A twelve year ground-based lightning dataset was used as a proxy for severe convective activity in this research as, unlike AWS, radar or satellite-based lightning detection data, dataset encompasses the whole New Zealand The main aims of this research, therefore, were to produce a spatial lightning climatology of New Zealand investigate the hypothesis that convective triggers leading to lightning activity in New Zealand are associated with different synoptic and local situations depending on time and geographic location. The purpose of this poster is to present the results of this high-resolution lightning climatological research in order to aid a better understanding of thunderstorm occurrence across New Zealand. There are different mechanisms for lightning. For example, lightning to the west of the Southern Alps in the South Island can occur under any weather situation at any time of the day or night and in any season of the year. Peak lightning occurrences are over and to the west of the seaward most mountain range, regardless of elevation. Lightning occurrence is highly influenced by topography in many places, most notably over the South Island, where the Southern Alps acts as a barrier. Applications include risk assessment, where research outcomes can be used to pinpoint the most vulnerable localities / regions for lightning hazards. This can be utilised by groups interested in weather-related risk assessment (e.g. local councils) to help mitigate injury, death, damage to property and livelihood. In addition, a detailed knowledge of where and when lightning occurs can also strengthen the advancement of nowcasting and forecasting techniques.