Storm-tide red-alert days 2020

Storm-tide red alerts are the highest high tide (also known as king tides) dates that Emergency Managers and Coastal Hazard Managers should write in their diaries and keep an eye on adverse weather (low barometric pressure, onshore winds), river levels and sea conditions (waves and swell).

The dates below are averaged across New Zealand. See tide forecasts for specific locations.

The following table shows the 2020 dates of the highest high tide "red alert" dates, and the lowest high tide "carefree" dates. It also includes dates when the moon's orbit brings it closest to [perigee] and furthest from [apogee] the earth.

2020: Range of dates collated across New Zealand

Red-alert dates (highest high tides)

[actual lunar perigee date]

Carefree dates (lowest high tides)

[actual lunar apogee date]

12-16 January [14 Jan]

 

 

3-4 February [30 Jan]

10-14 February [11 Feb]

 

 

4-March

9-14 March [10 Mar]

 

 

 

7-12 April [8 Apr]

 

 

 

6-11 May [6 May]

 

 

16-May [18 May]

4-8 June [3 Jun]

 

 

12-14 August [10 Aug]

19-23 August [21 Aug]

 

 

11-13 September

17-22 September [19 Sep]

 

 

10-12 October

15-22 October [17 Oct]

 

 

 

14-20 November [14 Nov]

 

 

 

13-18 December [13 Dec]

 

 

24-December [25 Dec]


Visual representation of this calendar:

  

2020 calendar of red alert high tide dates.

There is a printable version of the 2020 calendar available for download.

Regional red alert days

Red alert tide days are available for different regions throughout New Zealand. 

Further information

High perigean-spring tides, colloquially known as "king tides", peak 1–2 days after New or Full Moon when Moon is in its perigee (i.e., when it is closest to the Earth during its 27½ day elliptical circuit around the Earth), but dates of highest tides vary around New Zealand.

In 2020 the Moon's closest perigee occurs on 8 April* and coincides exactly with a Full Moon, with next closest on 17 October (New Moon). The year's highest high tides will occur in the two perigean phases of February to April and August to November.

For the year 2020, "red-alert" dates cluster around very high tides (perigean-spring tides) that peak 1–2 days after New or Full Moon when Moon is in its perigee and "carefree" dates cluster around lower high tides after First or Third Quarter when Moon is close to its apogee. 

Times for perigee, apogee and New and Full Moon in UTC (add 12 hours for NZST). 

Research subject: ClimateCoastsPhysicsTides