Tag Archives: weather

UK rainfall: Seathwaite / Honister v London

It’s been a wet winter so far. Some 177mm has fallen in Wanstead – already 122 per cent more what falls in an average winter.

But the amount pales into comparison with the Lake District. Since December 1st 1360mm has fallen at Honister, a station close to Seathwaite which proudly proclaims itself as ‘England’s wettest place’.

Over a calendar year the area usually sees 5.6 times the amount of rainfall of London. However, this winter the total of 1360mm makes it 7.7 times wetter! A testament to just how persistent the SW’ly airstreams have been this season. And a reminder that the Lake District is the called the Lake District for a reason.

Data from the excellent Starlings Roost Weather.

Wanstead weather in December

Continuing on from last month this blog focuses on the weather recorded at this station over the last 11 years.

A look at the twelfth month shows some interesting trends…

The 9am air pressure readings were not included in previous climate summaries owing to analogue barometers only giving approximate air pressure readings. The advent of AWS has changed that, particularly for independent amateur observers.

A look at the below graphic shows pressure falling through the first half of the month. A sharp rise is then seen before falling again – there’s often storms around the 23rd until the 27th.

Average daily windrun is how much wind there’s been during a 24 hour period. The 23rd comes out as windiest.

Average rainfall shows precipitation building through the month, to peak on the 23rd before a sharp drop off after the 27th.

Average daily maximum temperatures during December show a stuttering first 10 days before a steady rise through the next fortnight before a steady fall off from the 23rd .

Average daily minima is up and down in the first 10 days before a steady rise from the 11th. Again there’s that falling off a cliff on the 23rd.
This pivotal date, being so close to Christmas Day, is one of the reasons why ‘will it, won’t it be a white Christmas’ is a perennial fascination among the nation.

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London winter forecast 2023/24

The coming winter is likely to be mild and wet thanks to a predominant south-westerly Atlantic regime.

This year I have tried to improve my statistical method by using historic data from across the capital thanks to the Met Office’s ever expanding library of data; daily Kew values now date back to 1881!

In terms of rainfall and mean temperature a total of eight years were similar to this October and November, spanning 1929 to 2020.

The probabilities for the following DJF winter were thus.

Mean temperatureProbabilityRainfallProbability
Very mild37%Wet37%
Average to mild51%Average63%
Below average12%Dry0%
London winter forecast 2023/24

Looking deeper into the stats I had a look at the Oceanic Niño Index; the most similar years to this one were 1982 and 1987.

A note on WeatherWeb mentions exception rainfall in the Lewes & Brighton area of Sussex, between 20th September and 31st December 1982.

January 1988 was the wettest in England and Wales for over 40 years, and the wettest at Hampstead since records began there in 1909.

February of that winter also saw a major storm affecting much of the British Isles on the 10th and 11th with much damage to buildings.

The prognosis for snow at this point seems bleak – though chances may be heightened should we experience a stratospheric sudden warming in December / January. Though, as seen in 1987 where a vortex ‘split’ was recorded, this would still not guarantee wintry weather.

Taking the above years into account would give a winter where the average mean would follow this graph. Therefore, after the cold snap during the first week of December, the temperature gradually climbs through the month until the 18th when the will be a gradual drop for a possible cold snap between Christmas and New Year.

This then followed by the usual warm up in the new year with changeable weather through January. The best chance of a sustained cold snap appears to be from February 7th to 13th.

Disturbed autumn regimes

October 18th this year heralded a run of weather where it has hardly stopped raining in this part of the south-east.

Since that date there has been 101mm of rain with 22 ‘rain days’, 24 hour periods where there’s been 0.2mm of rain or more. Just one of the last 24 days has been completely dry.

In terms of the 1991-2020 average the amount represents just under twice the usual amount of rainfall at this time of year.

In terms of unusual weather patterns it is up there amongst the ‘top 10’.

What does it mean for the coming winter. Impossible to say on a small scale but I’m guessing wet and mild in the south. Note however that 1960/61 and 1998/99 had a number of maritime northerly outbreaks which added up to an average winter in Scotland, and plenty of snow for the Highlands.

Also note how similar this autumn is to last year when the snowy spell in December came out of nowhere.

The Hampshire tornado of December 1821

While researching an incident of very low pressure in 1821 I also found this account of a tornado that happened a couple of days later – not dissimilar to events earlier this month close to the south coast of England.

In The Climate of London, Luke Howard writes about an account of an ‘electrical whirlwind’ or spout in Hampshire.

On December 27th, two days after the record low pressure recorded in the London area, residents between the towns of Alresford and Alton witnessed a thunderstorm that was accompanied by torrents of hail, rain and gusty winds at 2.30pm.

A funnel was seen tapering gradually to the ground, the vortex bending from the prevailing SW’ly wind. Lasting for two minutes, according to one account, the whirlwind caused havoc as it carved a ‘serpentine chiefly in the direction of London Road’.

Its effects were restricted to a distance of two miles along a path of varying between 6ft and 20 yards in width.

One person described the tornado as a body of thick white mist tapering from the clouds and near the earth about the size of a woolpack. It appeared to him to touch the earth and bound from it repeatedly. Another witness who was nearer said he felt as if pails of water were thrown on him such was the effect of the strong electric aura attending it though there was no discharge of water at the time from the cloud.

The aftermath revealed a trail of destruction. An oak tree, a ‘foot and a half’ in diameter, was broken and carried upwards of 40 yards. Several fences were removed to a distance of many feet.

In the village of Ropley a farmhouse was damaged two barns were destroyed. Large elm trees were uprooted, a ‘fine walnut tree broken in half’ and gates, stiles and even thick gate posts were torn up.

The trees and ruins blocked the coach road and ‘it required some hours labour to clear them away’.

Looking at the possible track of the tornado it occurred close to the UK’s ‘tornado alley’!

Wanstead weather in November

The current site hosting Wanstead’s weather station has been running for 11 years this month; the automatic station uploading data every 10 minutes to the internet.

The 10-year averages from the station are now good enough to be listed on the Climatological Observers Link.

A look at the eleventh month shows some interesting trends…

The 9am air pressure readings were not included in previous climate summaries owing to analogue barometers only giving approximate air pressure readings. The advent of AWS has changed that, particularly for independent amateur observers.

A look at the below graphic shows pressure lowest around the 4th, the stormiest weather of the month. Storm Ciaran in 2023 is proof of that.

Average daily windrun is how much wind there’s been during a 24 hour period. The 21st comes out as windiest, the date when in the past there has been some notable early snowfalls in the south of the UK.

Average rainfall shows most precipitation in the first two thirds of the month with the biggest fall of rain on the 19th.

Average daily maximum temperatures during November take a general decline but, again, there’s a notable fall away on the 20th.

Average daily minima decline to the 5th (the 6th is the median for the first air frost) before increasing before falling away again after mid month.

Record low pressure of Christmas Day 1821

The lowest pressure recorded in the southern UK happened on February 25th 1989 when the barometer fell to 942.4mb.

I was also reminded this week of another occurrence of extraordinary low pressure in southern England on Christmas Day 1821. Luke Howard’s Climate of London recalls the event in his December summary where, he states, the air pressure fell to 27.83 inches (942.4mb).

This month is remarkable for a depression of the barometer which for London at least or its vicinity is nearly without a precedent on record. The lowest observation here given 27.83 in was obtained at Tottenham from a portable barometer of Sir H Englefield’s construction about 5am on the 25th.

Luke Howard

In what appears to be remarkably similar to what is unfolding with Storm Ciaran Howard added that despite the low pressure the weather on Christmas Day was ‘very fine’, a day that was sandwiched by much rainy weather.

In his entry Howard explains:

We had no storm of wind of any consequence after this great depression which it should be remarked had been coming on for about two weeks. It appears by the papers that a like state of the barometer was extensively observed at the same time on the continent and that very tempestuous weather attended it far to the south of our island.

Luke Howard

Howard also received a letter from Thomas Squire of Epping who wrote.

The fall of the barometer has been as wonderful as the fall of rain. On the 24th at midnight my barometer was 27.76 in. It continued nearly stationary till about six next morning when it was 27.73 in. This was its minimum altitude shortly after it began to rise at 8am.

Thomas Squire

Squire’s readings, taken at Epping (105m), can be adjusted for sea level and compared with the hourly trace for Storm Ciaran. Taking this into account the barometer actually bottomed out at 927.6mb! Plotted against Storm Ciaran the behaviours of the two depressions are remarkably similar.

Howard would go on to discuss his findings with the Royal Society the following month in January. He remarks that the low pressure was notable in that it happened in the same year that notably high pressure was recorded in the February. Just like this year! I recorded 1060.1mb on February 5th.

Though low by southern UK standards there have been many deeper depressions to the north.

Spend ÂŁ100k to save millions on flooding

The Met Office Library holds millions of daily rainfall observations in its archives. Though anyone can access these physical treasures in person, and on request by email, a lot of these records taken before 1960 remain hidden away.

Yet these data provide an excellent insight into the behaviour of our weather on a local scale. As good as computer models are they are still a distance away from being able to forecast thunderstorms and frontal rain at smaller resolutions. Data from the literally hundreds of smaller rainfall stations set up in Victorian times would provide local government agencies the ability to identify where rainfall is historically heaviest and therefore areas where flash flooding is a greater risk.

For a number of years some of the archives have been digitised with the help of citizen science campaigns; the records of the Ben Nevis Summit Observatory being one historic station now digitised.

Though AI has improved computers still struggle with handwritten records; the best method is still to scan them all by hand before an army of volunteers get to input them onto online spreadsheets.

The cost to scan the rainfall archive pre-1960 would be ÂŁ100,000. Though this sounds a lot for a ‘nice to have’ digital archive it could save millions in the cost of reactionary local authority work thanks to measures taken to plan against problems with flash flooding before they appear.

Wanstead weather in October

The current site hosting Wanstead’s weather station has been running for 11 years next month; the automatic station uploading data every 10 minutes to the internet.

The 10-year averages from the station are now good enough to be listed on the Climatological Observers Link.

A look at the tenth month shows some interesting trends…

The 9am air pressure readings were not included in previous climate summaries owing to analogue barometers only giving approximate air pressure readings. The advent of AWS has changed that, particularly for independent amateur observers.

A look at the below graphic shows pressure lowest around the 21st, the stormiest weather of the month. Storm Babet in 2023 is proof of that.

Average daily windrun is how much wind there’s been during a 24 hour period. Again the 21st comes out as windiest.

Average rainfall

Average daily maximum

Average daily minimum

‘White flakes falling on the city brown’

Written in 1890 this poem was composed when white Christmases were far more common.

LONDON SNOW by Robert Bridges

When men were all asleep the snow came flying,

In large white flakes falling on the city brown,

Stealthily and perpetually settling and loosely lying,

Hushing the latest traffic of the drowsy town;

Deadening, muffling, stifling its murmurs failing;

Lazily and incessantly floating down and down:

Silently sifting and veiling road, roof and railing;

Hiding difference, making unevenness even,

Into angles and crevices softly drifting and sailing.

All night it fell, and when full inches seven

It lay in the depth of its uncompacted brightness;

The clouds blew off from a high and frosty heaven;

And all woke earlier for the unaccustomed brightness

Of the winter dawning, the strange unheavenly glare:

The eye marveled–marveled at the dazzling whiteness;

The ear hearkened to the stillness of the solemn air;

No sound of wheel rumbling nor of foot falling,

And the busy morning cries came thin and spare.

Then boys I heard, as they went to school, calling,

They gathered up the crystal manna to freeze

Their tongues with tasting, their hands with snowballing;

Or rioted in a drift, plunging up to the knees;

Or peering up from under the white-mossed wonder,

“O look at the trees!” they cried, “O look at the trees!”

With lessened load a few carts creak and blunder,

Following along the white deserted way,

A country company long dispersed asunder:

When now already the sun, in pale display

Standing by Paul’s high dome, spread forth below

His sparkling beams, and awoke the stir of the day.

For now doors open, and war is waged with the snow;

And trains of somber men, past tale of number

Tread long brown paths, as toward their toil they go:

But even for them awhile no cares encumber

Their minds diverted; the daily word is unspoken,

The daily thoughts of labour and sorrow slumber

At the sight of the beauty that greets them, for the charm they have broken.