KEY INSIGHTS

• 1 month’s worth of rain fell in just 1 hour
  Based on Metservice data at their Auckland Aerodrome weather station:
  • The historical Auckland average in the month of January = 71.2mm (7.12 cm)
  • On January 27th between 7-8pm, the rainfall = 71.0mm (7.1cm)
• > 3 month’s worth of rain fell in just 1 day
  Based on Metservice data at their Auckland Airport weather station (AWS-90544):
  • 200.8 mm (20.1cm) falls on average between January-March each year
  • 258 mm (25.8cm) fell on January 27th alone

KEY QUESTION

1. Why was Auckland not alerted sooner?

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Full data analysis
Please contact us if you would like the full analysis. NOTE: you will need to contact Metservice directly for some of this information.

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Notes:

• Rainfall is typically measured in mm due to the small numbers. We decided to show it in cm in the graph to increase comprehension for the general public who use cm more often.
• Rainfall amounts differ between different weather stations.
• We choose Auckland Airport for six reasons:
  • It had the most robust current data set.
  • It had historical data to compare against.
  • Auckland Airport had some of the highest hourly rain figures.
  • The flooding at Auckland Airport was one of the most covered in media.
  • Trying to compare multiple weather stations on one graph looked messy.
  • We could not aggregate all Auckland weather stations as the export Excel function on http://cliflo.niwa.co.nz/ was not working. This would be a useful exercise for someone to do and share.
• The coordinates for the two weather stations used for this graph are:
  • Auckland Airport (AWS-90544) = -37.009,174.783
  • Auckland Aerodrome (NZAAA) = -37.009,174.807
• Metservice also sent us some data for:
  • Whenuapai Aerodrome (NZWPA)
  • Whangaparaoa (NZWHX)
• Metservice also said “The Auckland Council also operate an extensive network of rain gauges across the Auckland region. Their data can be found at: https://environmentauckland.org.nz/”
• All numbers are provisional and subject to revision.

Thank you to the Factors who helped pull this together.

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SOURCE:

• Daily and historic monthly rainfall = https://www.metservice.com/towns-cities/locations/auckland/past-weather
• Hourly rainfall over January = a custom report from Metservice

(c) Meteorological Service of New Zealand Limited

Licensed for use under the creative commons attribution licence (BY) 4.0

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Did we make a mistake, or have you got smarter data?  Let us know.