February 1986 was a very blocked month dominated by easterly winds. This is clearly evident from the NCEP 500mb height anomaly reanalysis below with an anomalous blocking area of high pressure centred over Iceland and equally below average heights over much of Europe but not too far north over Ireland to allow the easterly winds.
It was one of the most easterly months on record and most easterly February since 1947. We have not seen a Winter month as easterly as this one since.
As easterly winds were the dominance, it should be no surprise that February 1986 was a bitterly cold month. It had a Central England Temperature (CET) of -1.1c which makes it the 5th coldest February on record back to 1659.
The month was uniformly very cold and exceptionally dry. High pressure to the north and east of Ireland and low pressure systems moving into Europe off the south of the country were the major influences on the weather during February. There were occasional showers of snow, especially in parts of the north and east from 5th to 7th, and also some longer outbreaks of snow in southwestern areas due to the passing weather systems. The snow remained on the ground in eastern regions for a considerable period. Fortunately, Ireland escaped the worst effects of the prolonged cold spell compared to neighbouring countries even whilst being threatened by heavy snowfalls on a number of occasions.
It was an exceptionally dry February with it being the driest February on record for a number of Irish stations including Shannon Airport, Co. Clare and Birr, Co. Offaly. A few places had only 1% of their average February rainfall with isolated places having no precipitation at all throughout the month. This was the first of two months in 1986 to have such an occurrence - the other month being September. Many years tend to not have rainless months so it was highly unusual that 1986 contained two such months in isolated locations.
Whilst being bitterly cold (deviations from average between 2 to 4c below average against 1951-80), it was not as cold as February 1947 which was the holy grail of all cold and snowy Februaries. There was many instances of frost although they weren't severe for much of the period due to cloud or the easterly gales. Got to remember that there would have been very low windchill temperatures though with said gales even though the air temperature did not show it. Frosts were most severe around the 21st, 22nd and 27th. Casement Aerodrome, Co. Dublin recorded an air minimum of -6.9c on the 21st. Clones, Co. Monaghan recorded a grass minimum of -12.9c on the same day. Claremorris had a soil mean temperature of -0.1c during the last three days of the month (26th-28th).
Sunshine was variable. For most, sunshine totals were above normal for February but southern and eastern coastal areas had a duller than average month. It was very dull in the extreme south where totals were comparable to February 1985.
The pattern was already developing at the start of the month with a trough centred over France bringing in gale force easterly winds and high pressure to our northwest and north.
Pressure and 500mb heights lowered over mainland Europe in the following days with blocking anticyclones establishing to our north continuing to draw in an easterly wind. The first snowfalls appeared around the 5th and 6th generally and they were mainly light. Nevertheless, they were persistently lying on the ground for many days and failing to melt causing disruption.
High pressure collapsed over us and to our east when a depression was coming out of North America into the south of Greenland on the 9th whilst at the same time, heights were lowering over the Arctic. All of this is indicative of the North Atlantic jet stream intensifying which did happen with February 1986 but it was no ordinary scenario of just returning to westerlies.
Freezing fog and frost formed underneath this high pressure resulting in some very cold conditions for a few days, as if February 1986 wasn't cold already! Though there was relatively milder conditions on the 11th and 12th for the south and west of Ireland with winds veering more southeasterly and some outbreaks of rain. Still on the colder side of average with max temps in the mid single figures at best.
By the 13th, high pressure pushed up to Scandinavia forming a Scandi High blocking off the Atlantic from pushing through. After a few calm days, the winds began to strengthen to gale force again with more outbreaks of snow as precipitation turned to snow in the cold air to our southwest.
The Scandi High began to retrogress to Greenland through the days allowing easterly winds to continue and eventually calm down by the 18th.
There was a national demand record for electricity on 17th February 1986 with 2130 megawatts of power according to the Irish Times on 18th February. There was reports of poor visibility too as a result of haze and smog brought in from Britain with the easterly winds to Ireland. The record high demand for electricity was blamed on the poor visibility and cold temperatures.
Winds became very slack and calm especially on the 22nd with cold air entrenched over Ireland. This resulted in the coldest conditions generally for February 1986 and is comparable to the synoptics that brought the December 2010 extremely low temperatures. However, there was not as much snow this time around and the sun was stronger too, compared to December 2010.
The cold and dry weather just went on and on 'til the end of the month with high pressure in charge. Unlike February 1947, February 1986 was not an overly snowy month. The pattern changed when the new month of March began though with westerlies becoming established.
Fortunately, whilst February 1986 was a persistently cold month, Ireland was spared the worst of the cold compared to neighbouring countries.
Data from Met Éireann.
RTÉ Archives reports on February 1986.