The winds of fiscal change with tariffs and falling stocks may be circulating the world, but a peculiar blip in the global wind stream known as an ‘Omega Block’ has given a very settled spell of weather in our neck of the woods of late.
BY VINCENT O’SHEA
But firstly, before we delve into the exaltations (or maybe disappointments for some), we must recall the winter of 2024/25.
With the exception of a brief cold spell in early January, it was indeed milder and drier than the long- term average locally and that was the trend nationwide. However, we did have to contend with one or two named storms.
Additionally, West Cork had the highest average temperatures of any part of the country during the autumn of 2024.
Interestingly, the sea temperatures at the weather buoy M3 southwest of the Fastnet never fell below 11.5 degrees Celsius at any stage.
The recent month of March, just gone by, was also notable for being very mild, quite dry, and sunnier than what is typical.
There were even sightings of the African Hoopoe bird along this south coast, especially around the Mizen and Galley Head areas and on Cape Clear, as well as reports of Sahara dust deposits too.
Whether we like it or not, these events further reinforce the reality of climate change and the continuing upward march of air temperatures.
TV weather presentations and graphics usually display sea-level parameters such as atmospheric pressure, temperature maps, and rainfall distribution.
This is deliberate for clarity and brevity, but the weather does have a three-dimensional aspect and the wind circulations at altitude become very important.
We call these flow patterns the ‘general circulation’, and it steers the systems from a west to east direction in the northern hemisphere.
It usually has an undulating wavelike pattern. Surface depressions (low pressure) form under the troughs, while anticyclones (high pressure) form under the crests.
Occasionally a type of standing wave appears on the crests and interrupts the eastward progression of the highs and lows.
This we call an ‘Omega Block’ and it gets its name from the Greek letter Ω due to its shape, which is a sort of northwards bulge.
When these arise, we can get lengthy spells of dry settled weather that can last for many days and even weeks.
Depending on the time of year, they may sometimes result in heatwaves.
Over recent years extreme events abroad led to these being referred to as a ‘heat dome’.
This is exactly the case with our weather at the moment and for the past week or two, with a surface anticyclone firmly established in the vicinity of Ireland and northwest Europe. The high pressure/anticyclone was centred north of Scotland last week, and we were under the influence of its southern flank.
There was also a strong pressure gradient, meaning a brisk easterly airflow originating over the North Sea kept our exposed south-facing coasts cool, as well as the long wind track over the relatively cold English Channel and Celtic Sea.
It was noticeably cool with temperatures no higher than 10 or 11 degrees near the shores, but because of April’s higher solar radiation (insolation), temperatures were a few degrees higher inland and progressively so towards the west of Ireland, which had picked up the heat over land.
However, the whole system has become more firmly established over us this week, as the high has drifted south.
Winds have eased and temperatures have recovered well, with many places getting over 20 degrees Celsius widely in glorious sunshine. So, there is no reason to believe the ‘Blocking high’ won’t stay around for a little longer.
Rumour has it that bookies are giving odds of a recordbreaking warm April.
Looking at the computer models (European extended forecast Copernicus system), one would say it might not support this hypothesis however. It certainly tells us that the first half of April will be very warm and dry overall, but then things revert to near-normal for the second half.
As I write, there are tentative signs that things might become less settled at least for a while this coming week.
Theory has it that an effect with the polar vortex will re-establish the blocking effect in the run in to Easter.
But fingers crossed, the prediction by the bookies might yet turn out right. So, let’s cherish and enjoy the foretaste to a sunny and warm summer.
