Occurrence of potentially damaging wind

  • Image, Occurence of potentially daming winds.

    Strong wind events can cause significant damage, for example, to trees and buildings. They can occur with frontal weather systems and around strong convection events, such as thunderstorms. Global climate change may change the frequency of damaging wind events in almost all areas in New Zealand in winter and decrease the frequency in summer. Monitoring can help us gauge the potential of, and prepare for, such events.

    We classified Occurrence of potentially damaging wind as a case study.

    Key findings

    The occurrence of potentially damaging wind showed a statistically significant decrease in Wellington from 1975 to 2013.

    • Monthly records from Auckland and Christchurch also indicate a statistically significant decrease. However, due to missing records these results should be treated with caution.
    • On average, Auckland experiences 55 days a year with gusts greater than gale force (33 knots, approximately 60 km/h), Christchurch experiences 58 days, and Wellington around 200 days.
    Note: The selected sites have missing data for some years. Gusts above gale force – above 33 knots, approximately 60 km/h.

    Definition and methodology

    Information on the occurrence of potentially damaging wind measures the number of days a year when wind gusts exceed gale force (33 knots, approximately 60 km/h, 17 m/s), as measured by weather stations around New Zealand.

    Wind gusts that exceed gale force may not always cause damage, but they are a useful gauge of the potential for damaging wind events. According to the Beaufort wind scale, damage generally occurs during strong gales, violent storms, and hurricane events (WeatherOnline, nd; Meteorological Service of New Zealand, nd).

    Data is available for 30 climate stations but some sites have many years of missing data for 1975–2014. Even one or two days of missing data can mean that a whole month, and therefore a year, must be discarded. We are working with NIWA to develop infilling techniques for the missing data.

    Time will tell if decreases in the number of damaging wind events are part of a cycle or whether climate change will increase the intensity and frequency of damaging wind (eg Mullan et al, 2011).

    Data quality

    We classified Occurrence of potentially damaging wind as a case study.

    Relevance

     This case study is a direct measure of ‘The occurrence of extreme weather events’ topic.

    Accuracy

     The accuracy of the data source is of medium quality.

    See Data quality information for more detail.

    References

    Meteorological Service of New Zealand (nd). Measuring the wind. Accessed 4 June 2015 from http://metservice.com.

    Mullan, AB, Carey-Smith, T, Griffiths, G, & Sood, A (2011). Scenarios of storminess and regional wind extremes under climate change. NIWA client report: WLG2010-31. Available from www.niwa.co.nz.

    WeatherOnline (nd). Weather online. Accessed 4 June 2015 from www.weatheronline.co.nz.

     

    Published 21 October 2015

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