EUROPE: Europe's regions have come under pressure - both high and low, writes Brendan McWilliams
Very often towards the end of August, there are signs the Irish summer is drawing to a close.
It is common around this time of year for cooler air to move in from the northwest, frequently bringing with it a succession of fronts and active depressions, a foretaste of the inevitable autumn gales of the coming months.
We have seen it happen this year in the rather changeable weather we have experienced for the past week or so, compared to the warm, settled conditions we enjoyed earlier in the month. But this change of pattern, not entirely to our liking here, will bring a welcome relief to many parts of Europe suffering from contrasting extremes in recent weeks.
Weather maps for even a few days ago clearly show the origins of Europe's woes. An anticyclone lay to the west of Spain with a ridge of high pressure extending northeastwards to provide mainly dry, warm weather over most of Ireland and Britain, the northern parts of France and Germany, Portugal and a large area of Spain.
Portugal in particular has been for several months under the influence of this ridge, which maintained a dry, mainly northeasterly airflow over the country. And given a prolonged period of dry weather, all that is needed for a wildfire is a plentiful supply of fuel and a spark.
Wildfires became a problem in Portugal in early June. The country was sweltering under a major heat wave which brought with it the worst drought in 60 years, daytime temperatures in excess of 40 degrees, and serious difficulties for Portuguese agriculture. Other countries were affected too, with record temperatures for mid-June registered in neighbouring Spain and also in the northern half of France.
Meanwhile, however, in other parts of Europe, the weather pattern took its toll in a completely different way. Juxtaposed to the high pressure over northwestern Europe there was, for an extended period, a corresponding zone of low pressure extending over southern France, Switzerland, northern Italy and southern Germany, and eastwards into Romania and Bulgaria.
Areas of low pressure are regions of ascending air, and ascending air, accelerated by the continental summer heat, breeds massive thunderstorms. In this relatively static pressure pattern, thundery outbreaks of heavy rain persisted for days and days on end in many places; hence the floods.
As with the droughts to the northwest, the flooding affecting many parts of southern Europe did not appear suddenly today or yesterday. In early July, Bulgaria and Romania were already experiencing catastrophic flooding, with regular reports of people drowned, roads being washed away and hundreds left without a home. The flooding and torrential rain in these regions has, by and large, continued unabated since.
The prevailing pressure pattern over Europe this summer has not been unusual, but the same cannot be said of the extremes of weather which accompanied it. They come, moreover, only two years after the extraordinary European summer of 2003, when temperatures in parts of southern France were a full five to seven degrees above the long-term average, and when Switzerland, a country not given to extremes, was warmer than at anytime in the previous 250 years.
Climatologists looking at these latest happenings will wonder if they are further evidence of an emerging world more given to extremes of weather than we have been used to in the past.
But, in the meantime, the worst is probably over and the coolness of autumn will return a meteorologically chaotic continent to something near normality.