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He mōreareaHazards
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Me takatūBe Prepared
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He pārongo whaitakeUseful Information
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Mō MātouAbout Us
Auckland often experiences severe weather events that can affect broad areas and which can bring severe winds, heavy rain, flooding, thunderstorms, tornadoes, (ex)tropical cyclones, coastal inundation, and rough seas. These events may cause significant damage and disruption. Heavy rain associated with major storms is usually less intense, but much more widespread that it is with a thunderstorm. Therefore, rises in river levels and the onset of flooding brought about by widespread heavy rain tend to be slower but also long lasting
Severe weather may be:
Major storms are almost invariably associated with atmospheric lows (depressions). While lows are common in the Tasman Sea - New Zealand - Southwest Pacific area, only the occasional one has the right characteristics to significantly affect New Zealand. In short, it has to be the right storm in the right place at the right time.
Impacts include:
In New Zealand, MetService defines broad-scale severe weather as widespread (i.e, over an area of 1000 km2 or more):
Severe weather watches and warnings are issued by MetService.
Severe winds are gusts of wind which are strong enough to be dangerous for people or cause significant damage to buildings and property. They are typically associated with storm events that can occur at any time of the year. The greatest danger during severe wind events is from flying debris and falling trees.
Heavy rainfall can be hazardous if it continues for a long time. It can cause streams and rivers to rise rapidly, and cause landslides and floods. The rain can also cause stormwater drains in urban areas to overflow which can lead to flooding.
In Auckland, we have overland flow paths, which channel water when stormwater drains are full – these may include roads, parkland and even gardens, to channel rain away from houses. Extremely heavy rain may lead to flooding.
Thunderstorms are short-lived, existing for no more than one or two hours. They may cause lightning (thunder is just the sound of lightning) along with very heavy rain and sometimes hail, localised severe winds and tornadoes. MetService is responsible for issuing severe weather warnings in New Zealand and may issue a “Severe Thunderstorm” warning if appropriate.
MetService defines “Severe Thunderstorms” as those which may produce:
A tornado is a narrow, violently rotating column of air extending downwards to the ground from the base of a thunderstorm. Only thunderstorms that have a particular sort of rotating air column produce tornadoes and it is only when this rotating air column touches down to the ground, or gets very close to the ground, does it become a hazard to land- (or sea-) based activity. A waterspout is simply a tornado that occurs over a body of water.
Tornadoes occur infrequently in Auckland and are much smaller than those that occur in the Midwest of the USA. They are usually around a few tens of metres wide, have tracks a few kilometres long and have a short duration. Like all tornadoes, their damage paths are extremely localised.
They are impossible to predict because of their small size, short lifespan and tendency to form offshore.
The greatest danger during severe wind events is from flying debris and falling trees which can cause injury, loss of life and damage property.
What do I need to do to be ready?
Tropical cyclones typically form close to the equator in the southwest Pacific Ocean. Cyclones derive their energy from warm equatorial waters. Sometimes, but not always, cyclones migrate out of the tropics into the mid-latitudes, close to New Zealand. These are known as 'ex-tropical cyclones'.
Southwest Pacific cyclones tend to form between December and April with at least one ex-tropical cyclone passing within 500km of New Zealand most years. Each storm's severity depends on many factors including where the cyclone forms and the strength of the dominating La Niña or El Niño cycle.
The table below shows tropical storm classifications in the southwest Pacific.
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Storm Type |
Sustained wind (km/h) |
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Tropical depression |
<63 |
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Tropical cyclone category 1 |
63-125 (gales) |
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Tropical cyclone category 2 |
125-164 (destructive) |
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Tropical cyclone category 3 |
165-224 (very destructive) |
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Tropical cyclone category 4 |
225-279 (very destructive) |
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Tropical cyclone category 5 |
>280 (extremely destructive) |
Coastal inundation happens when the sea floods coastal land. This can also be intensified by rivers near the coast flooding at high tide. During severe storms Auckland’s low-lying coastline is prone to flooding.
Inundation is more likely to occur when high tides combine with strong onshore winds and low atmospheric pressure (storm surge). It can be affected by steep coastal slopes, and elevated river levels from heavy rainfall. During storm events, the likelihood and magnitude of coastal inundation is highly dependent on the particular occurrence or timing of high tides and their relative height, storm surge and accompanying wave/swell conditions.
Impacts include:
What do I need to do to be ready?
King Tide charts and dates are available to read through NIWA
Download King Tide chart for - West Auckland
Download King Tide chart for - East Auckland
