Tag Archives: East London weather

Sunless days and washouts

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 Wanstead Park

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 Thermometer: 9.1C (1.1C below average, coldest since 2013, 111th coldest) Rain Cloud with rain: 113mm (84% of average, wettest since 2018, 150th wettest ) Sun Sun with rays: 425.4 hrs (94% of average, dullest for three years. 51st dullest) The average masked extremes.

The coldest and wettest days of June

Looking out the window on a cold and miserable June afternoon yesterday reminded me of similar such days during the Seventies and Eighties.

But the mind plays tricks and I wondered if these kind of days were that common in the past.

To weed out the also-rans qualifying days had to be sunless with an anomaly that was at least 4C cooler than the daily average and rainfall of at least 12mm.

This gave the following list.

24hrd

So, in the last 60 years there have been only 12 days similar to June 10th 2019. That would give a probability of less than 1% (0.00743)

Looking elsewhere it would appear that there was much more rain to the north, south and west of Wanstead.

rain all

 

 

Where’s east London’s rain coming from?

April 2019 was yet another dry month. Just under 12mm was recorded, that’s 28 per cent of average.

There has been rain around but the prevailing wind has not been conducive for great amounts to fall here. Last weekend, over a period of 5 days, just 0.9mm fall. Yet Capel Curig in Snowdonia, 200 miles northwest as the crow flies, recorded 130mm thanks to a NW’ly regime.

A look at rainfall in Wanstead back to July 2013 shows that of the 3,550mm recorded just 17 per cent has fallen when the wind was NW’ly.

Because of the topography of the area most of our rain falls when the wind is blowing between SE’ly and SW’ly, a total of 43 per cent.

A westerly is usually reliable for rainfall, however because this area is in the lee of high ground areas such as Hampstead westerlies have delivered just under 8 per cent of that 6-year total.

rain rose

How April has warmed in London since 1980

april 1981-2019

The above graphic shows maxima recorded in the month of April with shading to represent the anomaly of each day relative to the 1981-2010 average.

The last two years show the warm spells experienced in the second half of the month. The overall impression is that warming seems to have accelerated since 2011.

 

Winter proper to arrive mid January

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.

jan max

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.

14th
The GFS has been churning out some very strange charts of late

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.

feb m

 

 

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.

 

 

First frosts in East London since 1959

Although many parts of the UK have already recorded their first air frost this part of the capital, being so built up and close to the City, remains frost free.

Although many may think that frosts are getting later a look back through local statistics to 1959 shows these events are very random.

The scatter graph below illustrates this.

first frost in east london a

Taking out the winters of 1974/75 and 2002/03, which didn’t see frosts until February and January respectively, the scatter can be seen better here.

first frost in east london b

The median for the first frost is November 6th with an average minimum of -1.4C.

October frosts can be a precursor to a mild winter much in the same way that heavy October snowfall in the Alps has lead to an awful season. But there are exceptions, as happened in 2008/09.

* To record an air frost the temperature must fall to -0.1C or lower.

London’s October extremes since 1959

October is one of those months that can see both ends of the spectrum; from calm ‘mists and mellow fruitfulness’ and, rarely, frost, to wet and wild systems whistling in off the Atlantic, best known being the 1987 Great Storm and, more recently, the St Jude storm.

I’ve put together a few top 10s of stats for Wanstead, St James’s Park and Heathrow for the month of October.

october extremes

October SJP

Heathrow oct

Some national UK October values according to TORRO

Hottest: 29.4C March, Cambs – 1st 1985
Coldest: -11C Dalwhinnie 28th 1948
Wettest: 208.3mm Loch Avoich 11th 1916

In terms of climatology October maxima, considering the 1981-2010 average, shows a decline through the month, though around the 8th and 20th there is often a spike. This would reflect the October singularities; early October storms, between 5th and 12th, peaking on the 9th, occur in 67 per cent of years. St Luke’s summer, between 16th and 20th, peaking on 19th, also has a 67 per cent probability.
Mid-autumn storms occur between 24th and 29th October, with a 100% probability.

october average graph

The average rainfall graphic shows that downpour amounts are variable through the month. A tendency for dry weather around the 17th and 18th before the wettest days on the 20th and 21st.

October rainfall

 

 

 

40C in London end of July? Probably not

The long range weather models are causing much excitement on various forums with one run predicting an anomaly of +16C on Sunday, July 29th.

july29th

Such an anomaly would see temperatures exceed 40C in London, unprecedented looking back at records to 1841; the highest temperature recorded in the UK was 38.5C at Brogdale, near Faversham, Kent, in Augut 2003.

Though it is improbable it is not impossible. Back in April conditions allowed the temperature to rocket to a monthly record of 29.1C, a positive anomaly of 15.5C!
A repeat of similar synoptic conditions would be needed – these would obviously be helped by the record meteorological drought conditions this area is currently experiencing.

Because reliable thermometer records of heatwaves only go back as far as 1840 it is impossible to quantify whether 40C has ever been exceeded in the UK prior to then.

However, accounts of the heatwave of July 1808 suggest parts of England may have come close. Far removed from images of freezing Georgian winters and miserable summers the July of 205 years ago was among the warmest ever. The monthly mean for July 1808, according to the Central England Temperature series, was 18.4C – the 6th hottest July since the beginning of the series in 1659.

Luke Howard, the ‘father of meteorology’ who at the time lived in Plaistow, referred to the heatwave in his diary on July 13th: “Temperature at 9am 84F. The intense heat of the maximum lasted nearly three hours till about 4pm. At 6pm the temperature was 90F.” Another entry mentions a reading taken nearby. “Another at Plashet, a mile and a half eastward, indicated 96F as the maximum under the shade of a house.”

While Howard’s methods of measuring the temperature ran short of modern standards, his thermometer was hung under a laurel bush, the values still give a valid insight into the heatwave.

Tales of the heatwave, which particularly affected east and north-east England, can be seen in letters sent to local newspapers around the country. Many describe labourers dying from heat exhaustion while working in fields. Farm animals and horses suffered a similar fate.

One letter from Hull, published in the Coventry Mercury, said: “At Sigglesthorne, the honey in some beehives melted, ran out upon the ground, and most of the bees drowned in it. At Sutton, a lamb and a dog belonging to the Rev Mr Croft of Rowley, expired in the heat; and several birds dropped down dead, while flying over the streets of this town.”
Of course it is impossible to know about the health of people and animals that died but that birds dropped out the sky suggests extreme heat.