Extreme weather events Data

DATA SOURCE: National Institute for Water and Atmospheric Research (NIWA)
[Technical report available at www.mfe.govt.nz/publications/environmental-reporti... and www.mfe.govt.nz/publications/environmental-reporti...]

Adapted by Ministry for the Environment and Statistics New Zealand to provide for environmental reporting transparency

Dataset used to develop the "Wildfire indicator [available at www.stats.govt.nz/indicators/wildfire-risk]

This indicator measures fire danger using the New Zealand Fire Danger Rating at 30 sites around New Zealand from 1997 to 2019, although not all sites start at 1997. We report on the number of days per year with ‘very high and extreme’ (VH+E) fire danger for each of these sites, and trends over time.

More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

DATA SOURCE: National Institute for Water and Atmospheric Research (NIWA)
[Technical report available at www.mfe.govt.nz/publications/environmental-reporti... and www.mfe.govt.nz/publications/environmental-reporti...]

Adapted by Ministry for the Environment and Statistics New Zealand to provide for environmental reporting transparency

Dataset used to develop the "Wildfire indicator [available at www.stats.govt.nz/indicators/wildfire-risk]

This indicator measures fire danger using the New Zealand Fire Danger Rating at 30 sites around New Zealand from 1997 to 2019, although not all sites start at 1997. We report on the number of days per year with ‘very high and extreme’ (VH+E) fire danger for each of these sites.

More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Trends in number of days with a maximum gust in the 99th percentile, 1972–2016. The number of days with a maximum gust in the 99th percentile provides information on the frequency of extreme wind events. Percentiles are obtained from all available daily maximum wind gust data. On average, the 99th percentile daily maximum wind gust will be exceeded on approximately 3.6 days per year. Therefore, annual counts higher than this indicate more days than usual with very strong wind gusts recorded; annual counts lower than 3.6 indicate fewer strong wind gust days than usual. By using a percentile threshold we can identify events that are extreme for a particular location. Some places are naturally subject to stronger winds than others, so vegetation can become ‘wind-hardened’ and may have a higher tolerance to high wind gusts (eg a 100 km/hr wind gust may be damaging at one location, but not at another). Using a relative threshold accounts for these differences and better captures extreme wind gust occurrences. The highest maximum gust per year and the average annual highest maximum wind gust both provide information on the magnitude of extreme wind events.
Steady wind can be an important resource, but strong gusts can damage property, topple trees, and disrupt transportation, communications, and electricity. Extreme wind events can occur with frontal weather systems, around strong convective storms such as thunderstorms, and with ex–tropical cyclones. Projections indicate climate change may alter the occurrence of extreme wind events, with the strength of extreme winds expected to increase over the southern half of the North Island and the South Island, especially east of the Southern Alps, and decrease from Northland to Bay of Plenty. Monitoring can help us gauge the potential of, and prepare for, such events.
Trend direction was assessed using the Theil-Sen estimator and the Two One-Sided Test (TOST) for equivalence at the 95% confidence level.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Trends in maximum highest annual wind gust, 1972–2016. The number of days with a maximum gust in the 99th percentile provides information on the frequency of extreme wind events. Percentiles are obtained from all available daily maximum wind gust data. On average, the 99th percentile daily maximum wind gust will be exceeded on approximately 3.6 days per year. Therefore, annual counts higher than this indicate more days than usual with very strong wind gusts recorded; annual counts lower than 3.6 indicate fewer strong wind gust days than usual. By using a percentile threshold we can identify events that are extreme for a particular location. Some places are naturally subject to stronger winds than others, so vegetation can become ‘wind-hardened’ and may have a higher tolerance to high wind gusts (eg a 100 km/hr wind gust may be damaging at one location, but not at another). Using a relative threshold accounts for these differences and better captures extreme wind gust occurrences. The highest maximum gust per year and the average annual highest maximum wind gust both provide information on the magnitude of extreme wind events.
Steady wind can be an important resource, but strong gusts can damage property, topple trees, and disrupt transportation, communications, and electricity. Extreme wind events can occur with frontal weather systems, around strong convective storms such as thunderstorms, and with ex–tropical cyclones. Projections indicate climate change may alter the occurrence of extreme wind events, with the strength of extreme winds expected to increase over the southern half of the North Island and the South Island, especially east of the Southern Alps, and decrease from Northland to Bay of Plenty. Monitoring can help us gauge the potential of, and prepare for, such events.
Trend direction was assessed using the Theil-Sen estimator and the Two One-Sided Test (TOST) for equivalence at the 95% confidence level.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Extreme weather events are weather events that are rare or even statistically unlikely. In New Zealand, such events can be dangerous and costly, both socially and monetarily. They can cause damage that affects productivity and leads to millions of dollars in insurance claims.
This dataset relates to the "Insurance losses for extreme weather events" measure on the Environmental Indicators, Te taiao Aotearoa website.

Lightning is the discharge of electricity from thunderstorms. Ground strikes can cause significant damage to property and infrastructure, and injure or kill people and livestock. Lightning is often associated with other severe weather events, such as strong wind gusts. Thunderstorms may increase in frequency and intensity with climate change.
This dataset relates to the "Lightning" measure on the Environmental Indicators, Te taiao Aotearoa website.

Lightning is the discharge of electricity from thunderstorms and can occur within a cloud, between clouds, or between a cloud and the ground. By international standards, lightning does not occur frequently around New Zealand. However, ground strikes can injure or kill people and livestock, damage property and infrastructure, and, although rarely in New Zealand, spark forest fires. Thunderstorms are often associated with other severe weather events, such as strong wind gusts and hail. Thunderstorms may increase in frequency and intensity with climate change.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Lightning is the discharge of electricity from thunderstorms and can occur within a cloud, between clouds, or between a cloud and the ground. By international standards, lightning does not occur frequently around New Zealand. However, ground strikes can injure or kill people and livestock, damage property and infrastructure, and, although rarely in New Zealand, spark forest fires. Thunderstorms are often associated with other severe weather events, such as strong wind gusts and hail. Thunderstorms may increase in frequency and intensity with climate change.
Trend direction was assessed using the Theil-Sen estimator and the Two One-Sided Test (TOST) for equivalence at the 95% confidence level.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Lightning is the discharge of electricity from thunderstorms and can occur within a cloud, between clouds, or between a cloud and the ground. By international standards, lightning does not occur frequently around New Zealand. However, ground strikes can injure or kill people and livestock, damage property and infrastructure, and, although rarely in New Zealand, spark forest fires. Thunderstorms are often associated with other severe weather events, such as strong wind gusts and hail. Thunderstorms may increase in frequency and intensity with climate change.
More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.

Lightning is the discharge of electricity, from thunderstorms, that equalises areas of positive and negative charge, for example, between a storm cloud and the ground. Thunderstorms form as a result of rapidly rising air with a high moisture content (humidity). On average, 1 in 10 lightning discharges strikes the ground (or sea) (Metservice, 2015). Lightning (and therefore thunderstorms) are also often associated with other severe weather events, such as strong wind gusts, and in extreme cases tornadoes.

By international standards, lightning does not occur frequently around New Zealand. However, thunderstorms, and thus lightning, can cause injury and damage (Ministry of Civil Defence and Emergency Management, 2010), and may increase in frequency and intensity with climate change (Mullen et. al., 2011).

This data shows the average annual number of lightning strikes per 25km square.

This dataset relates to the "Lightning" measure on the Environmental Indicators, Te taiao Aotearoa website.

Geometry: grid/point

Unit: strikes/25km2/year

Further information can be found in:

MetService (nd). Lightning observation services. Accessed 3 June 2015 from www.metservice.com.

Ministry of Civil Defence and Emergency Management (2010). Thunderstorms. Working from the same page: Consistent messages for CDEM (p3). Available from www.civildefence.govt.nz.

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