Category Archives: singularities

The curse of June 13th

1 Jun 21 Jun 16 Jun 77

June can be a strange month weatherwise. Scorching temperatures as well as washout, cold weather, perhaps epitomised by the Queen’s Diamond Jubilee pageant on the river Thames in 2012, can feature prominently.

The month can also throw up some striking anomalies, none more so than the fact that the 13th is the only day in the month where the temperature has ever reached or exceeded 30C anywhere in the British Isles.

According to TORRO the highest daily maximum recorded in the UK is 28.3C at Earls Colne, Essex, in 1948; at Brixton, south London, in 1896 and Aboyne in 1994. Yet either side of this date has records comfortably above 31C, as the table below shows.

torro.PNG

The closest we’ve got locally to 30C in the last 60 years was in 1989 when 27C was recorded.

So why is the 13th ‘cursed’ with traditionally being the coolest day of the month? The best explaination perhaps is the fact that the date occurs more or less during the middle of the North-west European monsoon.

According to Philip Eden’s list of singularities the June monsoon can strike any time between the 1st and 21st but normally peaks on the 16th with a 77 per cent frequency.

As well as cool temperatures the phenomenon can also bring copious amounts of rain, as happened in 1903 when large parts of Redbridge were inundated following a 59-hour deluge that started on… the 13th.

Will we see a repeat this Thursday? Unlikely, though the general pattern is not that different to what led to events over a hundred years ago.

13th

 

 

A winter drought

Rain today (January 16th) is the first meaningful fall since before Christmas, putting an end to the 23-day long dry spell.

This meteorological drought, rare given that it spanned Christmas and New Year Storm singularities, these having 84 and 86 per cent probabilities respectively, was the 3rd equal longest winter drought.

The only other similar droughts in a list that dates back to 1887 were 19/12/2008 – 03/01/2009 and 17/12/1972 – 02/01/1973.

winter droughts

The last precipitation I recorded was from a weak occlusion that followed a cold front on the evening of December 23rd.

This synoptic set-up was followed by a build in air pressure that peaked on the morning of January 3rd; 1043.8mb was the highest reading in this area for at least 10 years and is the highest pressure I have measured.

A fuller version of London droughts in all seasons can be found here.

November: an Indian summer before turning cold?

With the mean temperature of both October and September finishing 0.2C below average it is probably safe to say that the weather is in an average kind of mood.

Conditions during the first part of November look changeable, according to the Met Office’s 30-day forecast . After mid month, however, the agency says the forecast is uncertain.

Now that much of the UK has had its first frost any warm spell in November will, correctly, be called an Indian summer. A singularity called the St Martin’s Summer occurs in 66 per cent of years, occurring between 15th and 21st and peaking on the 18th.

And, as if by magic, the GFS model today has this chart for the 16th, an Atlantic ridge of high pressure with daytime temperatures about 6C to 8C above average. Though warm during the day I would imagine there being a risk of fog forming at night

16th

Beyond that there could be a tendency for much more unsettled weather at the end of the month. The early December storms singularity occurs in 98 per cent of years, starting between November 24th and December 14th, often peaking on December 9th.

November, the last autumn month, can often surprise with its extremes, though it can also often be characterised by days of anticyclonic gloom. The warmest, coldest and wettest November conditions in London back to 1959 can be found here.