What brings good summers to Ireland
MONDAY JANUARY 01, 0001
1976/7 is one 18-19 year moon cycle onwards from 1959, which brought a glorious summer. It is also one moon cycle before 1995 which was equally memorable, and exactly another moon cycle before 2013, which we all fondly recall was a summer seemingly one out the bag. Accordingly before 1959 there were the good summers of 1940/41, 1921-23 and 1906. 1968 was a 9-year half cycle before 1977.
There have also been other good summers in other years due to solar factors. June-August of 1975, 1976 and 1977 brought memorably good summer weather due to both. Very sunny NE to SE winds prevailed. The poor summers of 1978 and 1979 saw a decrease in easterly winds and a rise in the dull cooling winds from the NW. Poor summers are those where westerly patterns predominate.
Lunar perigee is another factor. Once every 27.5-day month the moon drifts closer to earth then backs away again, called perigee by astrologers and astronomers. Perigee distance varies during the year and exactly which months have closer perigees repeats every 4-5 years. Closer perigees over the summer months bring better summer weather. An example was 1938, when Limerick experienced 37 consecutive days with no rain.
The effect of perigee is to exaggerate the season. Whatever weather is about during perigee increases in intensity. Close summer perigees bring heat, close winter perigees, more cold. Close spring perigees invariably bring wind. In 2015 the closer perigees were over February and March which accounted for the cooler spring conditions, but close perigees then were gone until autumn. As a comparison, in 2013 the closer perigees were in June and July.
Sometimes there is a northward surge of the Azores high, often as a ridge towards England or just generally northwards, which bring winds from W or SW which can bring a dry warm and humid air in July to Ireland. West and SW coasts remain dull, misty and sometimes drizzly but more sheltered areas receive the sun and the SE can become sunny and warm. Meanwhile the far north of the country may remain in the regime of the Atlantic fronts and continue unsettled although amounts of rain may decrease.
If an anticyclone (wind systems circling clockwise) occurs to the west of Ireland with cooler air drawn over the country from the NW the country may remain cloudy and possibly cool and gloomy day after day. The SW then gets the best weather and the northern counties get chilly showers near their coasts. Such summers occurred in the 1960s, e.g.1965.
But easterly winds are the best sign. Really fine weather for Ireland only occurs if westerly wind systems break down. A high pressure system over the southern North Sea that brings hot air from the Continent over the British Isles, usually with SE winds, will lower wind speeds over Ireland and allow heat to develop. If an anticyclone positions itself so as to bring winds from the NE and SE, Ireland receives long summer days with unbroken sunshine and soaring temperatures.
Usually the northward surge of pressure extends right over the British Isles to form a high cell over or near Scotland. This draws a large mass of warmed air over Ireland from the west of Spain which becomes, for Ireland a heatwave recipe. Examples have been July 1955, June 1957 and July 1977. Prolonged sunshine will result with winds are from the NE or E of Scotland when the air source is from Scandanavia or even the Arctic with temperatures over 20C from May to mid-September. Such occurred in August 1968, June 1976 and August 1977. In Donegal some still maintain 1968 was the best summer of last century.
In 2018 the second closest perigee will occur in mid July, but it will bring rain. However the full moons at the end of the months will bring very warm weather. For the next brilliant summer you must wait for 2022.