THERE was a new moon at perigee some days ago, which explains in part the seas of trouble experienced along our western coasts. Of course, the weather played its part as well - and so too did the sun, even if it was not very much in evidence. Coastal flooding of this kind requires a coincidence of meteorological and astronomical factors to bring out the worst.
The tides, as we know, rise and fall because the oceans on our revolving planet are subject to the gravitational attraction of other bodies in the solar system. By far the most important in this respect are the sun and the moon, and twice a month they co-operate fully with one another. At new moon and at full moon the sun, the earth and the moon are virtually in a straight line - with the two bodies pulling together, as it were, the high tides are higher than usual. We call, them spring tides, a named which has nothing whatever to do with the season of spring.
Other astronomical coincidences can make matters worse. At certain times in every revolution, the moon is at its perigee - the nearest point to earth - and its gravitational attraction is correspondingly enhanced. So a perigee spring tide is higher still. And the distance between the sun and the earth also varies; the sun is at its closest around: this time of the year - in early January to be precise - so a perigee spring tide in the early months of the year is very, very high indeed.
Meteorological factors also play their part. If the pressure pattern is such that strong winds can act on a stretch of water over a long distance - if they have what we call a long fetch - they pile up water, as it were, against adjacent coastlines, causing an increase of several feet in sea level.
And if you happened to look at the weather map during the recent floods, you would have seen that it was dominated by a complex low pressure system in the vicinity of Iceland, providing an almost straight flow of very strong winds right across the Atlantic; these winds had almost the entire distance from Newfoundland to Galway to work steadily on the waves and make them monsters.
Luckily, such coincidences are not too common, but when they occur they are very long remembered. One of the most spectacular occurred in December, 1942, when high tides and huge waves caused extensive damage around the southwest coast. Five people were drowned in Cork Harbour, the seas demolished the pier at Schull and the sea wall at Dingle, and dozens of boats were swept out to sea and lost.