CHRISTCHURCH council warns us of ‘a number of super-tides’ between April and September this year (Echo, February 19) due to a ‘19-year natural cycle’.
With the flooding reported soon after (Echo, February 21), the warning may have appeared more worrisome.
Yet the highest local astrological tide in 19 years is not this year but in 2024 according to the National Oceanography Centre and, at just five inches above the average maximum equinoxial tide, that hardly deserves the name ‘super-tide’.
The twice-monthly ‘spring’ tides are biggest when the spin of the Earth and the Sun line up with the Moon during the equinoxes.
The 19-year cycle dictates most of this alignment but this year other factors are at play.
On top of this 19-year cycle, the Moon’s elliptical orbit precesses round in 8.85 years and the plane of the lunar orbit precesses round in 18.6 years.
This year, these cycles all combine to increase our ‘spring’ tides this coming autumn, with the second highest tide during the 19-year cycle being in September this year.
The late August spring tide also makes the top 10.
Yet the few extra inches above average from these astrological tides is hardly ‘super’.
Tidal surges from the weather are getting more frequent and they can raise the high tide by more than a metre, even round here in the sheltered English Channel.
DR MARTIN RODGER,
Bloxworth Road, Parkstone
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