The coastal flooding during the first week of January along the Northumberland shore was unusually severe because it coincided with an astronomical event called the perigean syzygy. A tidal effect will get stronger when syzygy and perigee occur close together. Maximal tide raising forces occur only when the Sun and Moon are in direct mutual alignment. This occurs at syzygy (either full Moon or new Moon). This usually occurs when the moon is at the closest approach to the Earth or at perigee.
During the full and new Moon, the greatest difference between high and low tide water levels occurs. If the Moon is at perigee, the closest it approaches Earth in its orbit, the tides are especially high and low.
The changing distance of the Moon from the Earth also affects tide heights. When the Moon is at perigee the range is increased, and when it is at apogee the range is reduced. Perigee coincides with either a new or full moon causing perigean tides with the largest tidal range. If a storm happens to be moving onshore at this time, the consequences (in the form of property damage, etc.) can be especially severe.
Remember the Saxby Gale occurred during a perigean Spring Tide: Named not for the season of Spring, but from the German springen (to leap up). This tide that is of increased range occurs at the two times of syzygy each month during the full or new Moon.
According to letter to the editor written by Ivan Smith from Canning, Nova Scotia which appeared in the Chronicle Herald,
The near future is interesting. A more powerful perigean syzygy will occur during the wee hours on Jan. 30, 2010, when syzygy and perigee will be less than three hours apart. If an intense (low barometric pressure) storm should happen to form during the last weekend of this month, coastal communities can expect serious flooding to occur at the time of high tide.
The Farmer’s Almanac says that we are in for snow and stormy weather for the last weekend in January. The moon, which has a strange but real pull on the Earth, its oceans and the human psyche, will possibly show its real force on the ocean’s tides at the end of the month of January when its tug will be a tad stronger than usual. Can we expect another severe storm and tidal surge? That is the question.
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Amherst, Nova Scotia January 30th 2010.
ReplyDeleteWe certainly received a significant snow storm over the past 36 hours but as I awoke this morning there was blue sky and a driveway full of snow to greet me. As far as storm surge goes I think this area did not get one that was as damaging as the storm surge earlier in the month of January. I believe that most storm surge damage happened in Cape Breton and probably some on Prince Edward Island.