Installation failed...Spring on hold for now

Once again, the new working week begins as it has done so many times since mid-February with below average temperatures for the time of year. The Celtic Spring (as opposed to the meteorological or astrological season) is almost two thirds over and the Celtic summer is less than 5 weeks away but wintry conditions continue to dominate our weather.

There remains no real sign of a significant warming trend over the next week or so although there will be a slight improvement in temperatures during Easter Weekend.

The main reason for the unseasonably cold weather is that higher than normal pressure in the Arctic has displaced cold air southward over Siberia and Scandinavia, eventually making its way across the Continent to Ireland and Britain. This blocking setup in turn diverts the jetstream further south over Iberia.

As the below GFS pressure chart from illustrates, the air over Ireland is originating from a much colder European continent where cold weather has been entrenched for some weeks. As air circulates clockwise around high pressure systems, the position of the massive high pressure system to our north ensures that the cold air will be transported west towards us.
Click to enlarge.
The weekend snowfall was the result of an Atlantic weather system pushing up against the colder airmass. Rain turned to snow where this boundary line occurred (east and north Ulster). See the frontal system in this EUMETSAT video.

A near-record negative article oscillation index (AO Index) further illustrates the degree to which Arctic air has penetrated into the middle latitudes. A repeat of such a setup in mid-Winter would have delivered conditions equivalent to if not worse and more prolonged than those experienced during December 2010.

Though it is hard to consider snowfall being possible in Ireland in late March and early April, such a scenario is not unprecedented in Ireland. The collective memory when it comes to our climate can often be quite short. Even last year, Ireland experienced freezing conditions in early April after a late March that brought temperatures in the low 20s (c) to many parts.

Down through history, Ireland has experienced blasts of wintry weather late into the Celtic spring season. The early months of 1947 saw one of the most persistent cold spell of the century, with snowfalls affecting all parts of the country from late January until mid-March. In 1908, much Leinster and east Munster was affected by heavy snow in late April. In mid-March 1886, a great blizzard with snow depths up to 60cm struck Ulster.  A couple of weeks later between April 7th and 10th there was heavy snow, especially in the West and Midlands.

On average, Malin Head in Donegal records 2.3 days of lying snow each April compared to 2.0 in Mullingar (Westmeath) and 1.9 in Claremorris (Mayo). Snow has also been reported in May and September. On some of these occasions the falls have been considerable but the snow melted quickly. Interestingly, Clones in Monaghan records 0.4 snow days each May according to Met √Čireann's official figures for the period 1980-2011.

See our long range forecast for more on the coming week's weather.

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TMT article written by Mark Dunphy
A buzzard over Co Antrim on Sunday. Pic Brian McCullough