Supermoon 2015 expected to cause highest ‘super tides’ for 19 years

Sea levels to be 50cm higher this week as rare set of astronomical forces align

David Trayner
Sunday 27 September 2015 17:51
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The Supermoon is also coinciding with a 'Blood Moon', when the satellite turns red
The Supermoon is also coinciding with a 'Blood Moon', when the satellite turns red

Coastal towns are braced for the highest ‘super tides’ in 19 years as a rare set of astronomical forces align.

Sea levels are expected to be 50cm higher than a normal spring tide this week as a so-called Supermoon – when the Moon is at the closest part of its orbit – combines with an alignment of the Sun, Moon and Earth to create a perfect storm of cosmic forces.

Tides are governed by the gravitational pull of the moon and, to a lesser extent, the Sun.

Because the Sun and Moon go through different alignment, this affects the size of the tides.

Tidal forces are strengthened if the moon is closest to Earth in its elliptical orbit and when the Sun and Moon are directly over the equator.

Many areas of East Anglia, the South West and the Thames Estuary flooded in December 2013

The Moon’s orbit takes it over the equator every 27.2 days and the Sun reaches the same point twice a year, at the spring and autumn equinox.

This week these events have coincided with the two bodies aligning on the same side of the Earth – further magnifying their gravitational pull – and Moon being at the closest point of its orbit.

But, despite the highest ‘astronomical’ tide for 19 years, no coastal flood warnings have been issued as high pressure should protect the UK from high water.

Weather can have an even greater effect on sea levels than astral bodies.

Strong winds can pile up water on coastlines and low pressure systems can also cause a localised rise in sea level.

An estimated 2,800 properties – from East Anglia to Somerset - were flooded in December 2013 after the weather created a storm surge.

Watch the video below for Nasa's explanation of why the spectacle happens:

High pressure this week means wind levels should low and high pressure will effectively push down on the sea, driving down tide levels.

John Curtin, the Environment Agency’s interim executive director of flood and coastal risk management, said: “The flood risk is low over the next few days. Some of the highest spring tides of the year start this weekend but as we are not expecting any unsettled weather, it is unlikely that this will lead to flooding of coastal locations.

“The Environment Agency is monitoring the situation closely alongside the Met Office and local authorities, and will issue flood alerts and warnings if required.”

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