The crux of the article is that certain weather types can repeat at the same time of year with one having a 100 per cent probability!
The Christmas storm singularity occurs in 84 per cent of years.
While 84 per cent certainly doesn’t mean ‘nailed on’, in the current set up of models being evenly spread between settled and stormy it can be safely guessed at this range that there will be unsettled weather around on the 25th. Whether it will affect the whole country remains uncertain.
The last big snorter of a Christmas storm I can remember in London was 2013. The entry for the 23rd into the 24th reads.
“Cloudy and breezy start grew steadily duller with rain just before noon. Rain grew heavier with some really strong gusts into evening culminating at 2am. Cloud at one point was 10kms thick. Three deaths related to weather.”
There was chaos nationwide with flooding and power cuts.
Compiling a list of sunless, rainy days revealed some interesting spells of wet weather – the most miserable runs of June days in the capital since 1959.
First up was a three-day spell starting on June 25, 1974. Some 34.3mm of rain was recorded.
Next was a three-day spell starting on June 23, 1991. Some 26.3mm of rain was recorded.
Another three-day spell started on June 25, 1997. Some 36.2mm of rain was recorded.
Finally, and most recently, a two-day spell this month that began on June 17th. Some 28mm of rain was recorded.
The above spells all happened around the date of the ‘June monsoon’ singularity which has a probability of 77 per cent. Though the fact that these occurred 47 years, 30 years and 24 years ago shows that these extreme cases happen a lot less than three years in every four the singularity would suggest.
Comparing the current Northern Hemisphere pattern with 1974 suggests that while there’s just as much heat around at 850mb as there was 47 years ago, including an extreme heatwave over some Nordic countries, the air above Greenland appears colder.
The weather of late has been in stark contrast to the mostly dry, sunny (if a bit chilly) spring many enjoyed. Indeed the first half of June saw more of the same and, locally, was the warmest start to the first meteorological summer month since at least 1959.
My memory of summers years ago was that it was often hot and sunny but I also remember countless days of staring out the window for hours waiting for relentless rain to let up.
Looking back at sunshine stats to 1959 there has been over 4,400 days where no sun was recorded, roughly a one in five chance of a totally cloudy day.
Considering the months where the absence of sun is most noticed, May to October inclusive, the probability decreases to just under one in ten.
To decant these to ‘washout days’ I’ve only included those sunless days that were also ‘wet days’ where 1mm or more of rain was recorded. The probability further decreases to just under one in twenty.
All very interesting but were there more washout days decades ago or is the memory playing tricks?
Looking overall shows an increase since 2013. Out of all the months the most notable change has been August.
Spring in this neck of the woods was really mixed.
A chilly start to March became fairly benign before ending with the warmest March day locally since at least 1959.
April then turned much colder and drier; just 2.4mm of rain fell during the month – the driest April since 2007 and fourth driest in a local rainfall series back to 1797! Sunshine was abundant with over 200 hours. But clear skies at that time of year, with a polar continental airmass, often means air frost. And the ten recorded overnight was far higher than normal.
May saw things warm up slightly but the month still finished a degree colder than average. Some 80mm of rain fell which is over one and a half times what we’d normally expect. The wettest May since 2007 – the month playing catch up on the total absence of April showers that bring the spring flowers! It was a dull month with only 126 hours of sunshine, 69 per cent of average – the dullest since 1990 was third dullest back to 1881.
In terms of flora and fauna the colder weather played havoc with the trees, bud burst coming much later than recent years. As I write this on June 6th some of the later budders like false acacia have only just come into full leaf. The birds, as they normally do, just seem to get on with it raising their young. I’m not sure what the food supply has been like but judging by the amount of healthy juvenile fledglings I’ve seen I would guess that it has been a good season so far?
Here’s the stats. March 8C (+0.3) 30.9mm (76%) 90.9 hours (84%)24.1C on 30th (a record that had stood since 1965) April 7.2C (-2.6) 2.4mm (5.5%) 202.6 hours (127%) 10 air frosts in April, much higher than normal May 12.1 (-1) 80mm (156%) 125.6hours (69%) Spring 2021: Mean : 9.1C (1.1C below average, coldest since 2013, 111th coldest) Rain : 113mm (84% of average, wettest since 2018, 150th wettest ) Sun : 425.4 hrs (94% of average, dullest for three years. 51st dullest) The average masked extremes.
During a miserably cold and wet stroll around the golf course in Wanstead Park I happened upon the remains of Wanstead House – basically a deep excavation where the basement and kitchens once were.
As a freezing cold mixture of rain, sleet and snow fell, gradually thawing the remnants of last night’s snow, I wondered what the weather was like when this magnificent building last stood. Luke Howard’s entry in The Climate of London revealed that the weather on this day 200 years ago was remarkably similar.
Wanstead House around 1819 just before its destruction
February 1st 2019
As I stood and tried to imagine what the house must have looked like it occurred to me that 200 years is a mere blip in time in the history of the Earth. People come and go, buildings rise and fall but the weather goes on and on.
* There’s a fascinating extract on Wanstead from James Dugdale’s The New
British Traveller (1819) that you can find here.
** This video clip shows the site where Wanstead House once stood.
Weather models are continuing to struggle in the aftermath of the stratospheric sudden warming on January 1st. The GFS and ECMWF have flip-flopped: on one run decent northern blocking extends southward only for the dreaded European high to appear on the next.
Using a combination of QBO and ENSO data featured in my winter forecast and statistics from previous SSWs (including 2013 and 2018) achieved the following results shown in this graphic.
Although some days in the next week or so will be cold it is not until the 14th that conditions start to bite, the start of a week-long cold spell that will probably be more notable for cold than snowfall.
The rapid recovery in temperature would suggest that the Azores / European high making a return. With the MJO moving back and forth between phase 7 and 8, and looking at the behaviour of previous cold spells, this would make sense.
As for February, unless there are further SSWs to disrupt the polar vortex, and depending on its recovery, it is unlikely we will see a repeat of the winter of 1984/85 that I hinted at last month. The graphic below, however, would suggest another cold spell in the third week of February.
Lewisham’s Beckenham Place Park will next year be home to a new wild swimming lake, thanks to a plan to make London the world’s first National Park City.
The scheme put me in mind of the Shoulder of Mutton lake in Wanstead Park which, decades ago, used to host swimming galas and other events. Long-time residents of Aldersbrook will remember the jetty and diving board that stood at the edge of the lake before falling into disrepair that led to their removal.
With millions set to be spent shoring up the dams of the park’s lake system it is surely feasible that the City of London Corporation can reopen Shoulder of Mutton to swimming while the work is undertaken.
While being cheaper than a lido it would provide an excellent resource and give local residents the chance to enjoy once more swimming in natural surroundings, just like in the Serpentine and Hampstead Ponds.
I normally headline these monthly reviews by referring to the most notable weather but this April, often a fairly non-descript mid-spring affair, offered pretty much every type of weather.
The mean temperature finished 11.7C, 1.9C above average and the warmest for four years.
Rainfall was 55mm, 129 per cent of average and the wettest for 6 years.
Sunshine was just 110 hours, the dullest for 40 years and the 16th dullest since 1881.
Hidden in the positive monthly anomaly was the warmest April day in a local record going back to 1959: 29.1C on the 19th – a figure that represents a positive anomaly of 15.5C and occurring at the start of the warmest April heatwave since 2011. It was remarkable that such an anomaly happened so close to a record negative anomaly the previous month.
Yet, just over a week later, temperatures lurched cold again with one of coldest last days of April on record. Though the 24hr record wasn’t broken the noon-6pm record going back 60 years was beaten.
The wettest day occurred on the 9th with 10mm falling.