All posts by wansteadmeteo

A blog that tries to make sense of how the UK's national climate translates into local weather for Wanstead and the surrounding regions of east London and west Essex. Check out my twitter feed @wanstead_meteo for local weather forecasts, stats, records and phenomena for the east London areas of Wanstead, Aldersbrook, Leytonstone and Stratford. And anything else weather

200 years ago: the last Thames Frost Fair

The Frost Fair of 1814 on the River Thames in London. Painting by Luke Clenell, entitled The Fair on the Thames, February 4th 1814
The Frost Fair of 1814 on the River Thames in London. Painting by Luke Clenell, entitled The Fair on the Thames, February 4th 1814

It is 200 years ago this month that London enjoyed its last frost fair.

Weeks of hard frost from the day after Boxing Day was enough to freeze the river between the old London Bridge and Blackfriars, enabling dozens of opportunist London traders to set up stalls and booths selling souvenirs, drinks and food.

Unlicensed gambling, drinking and dancing was the order of the day for those brave enough to venture on to the ice. A sheep was roasted on the ice with the public charged to look at it, and charged again for a slice of “Lapland mutton”. At one point an elephant was led across the ice at Blackfriars.

The ice was however, not very stable. Boatmen deprived of an income charged visitors a penny to cross planks to get on to the ice. They were on hand to rescue two women who fell through, although a plumber carrying lead was not so lucky.

Though changes to the flow of the Thames has vastly reduced any chance of a frost fair being repeated I’ve often wondered what the day to day climate would have to be like to freeze the Thames as it did in 1814.

Luke Howard’s Climate of London provided a starting point. His pioneering measurements of the atmosphere taken outside his laboratory by the River Lea in Stratford, though not as accurate as today’s readings, provide an excellent insight into just how cold the season was.

Winter 1813/14 and 1962/63
This line chart shows that the winters of 1813/14 and 1962/63 bore some resemblance

I was surprised to find that the stats compare well with the winter of 1962/63 – the coldest winter in recent memory. Obviously Howard’s readings would not have been as accurate as today’s – his thermometers were initially suspended in a laurel bush to shield solar radiation – but they would still have been close.

I have converted his readings  in Fahrenheit to Celsius and plotted them on a spreadsheet here. As well as records of temperature, wind, rain and moon phase Howard also included any notable weather events in his diaries from both home and abroad.

The winter of 1813/14 started mild. On December 16th he noted that “bees quit the hive in unusual numbers for the season”. During the following days up to Christmas Day wind and rain alternated with misty, occasionally frosty, mornings – probably not unlike some of the weather we experienced last month.

However, Boxing Day brought a big change: “Since the 26th we have had a succession of thick fogs with a calm air or at most a breeze from the NE. Yesterday the air cleared a little and today has been fine; a display of cirrus clouds with much red in the morning and evening sky,  the peculiar smell of electricity has been perceptible of late when the air cleared up at sunset.” Howard goes on to report that there was an eruption of Mt Vesuvius in Italy.

The beginning of January saw the mists thicken into heavy freezing fogs: “The mists which have again prevailed for several days and which have rendered travelling dangerous.”

The view across to St Paul's Cathedral from Bankside at low tide by Wanstead_meteo
The view across to St Paul’s from Bankside at low tide. Images of what it looked like this month in 1814 can be seen on the Corporation of London’s website

In those days, with cloud identification in its infancy, Howard identified the fog as stratus and noted with wonder the formation of rime frost on everyday objects: “The air has been in effect loaded with particles of freezing water such as in a higher region would have produced snow.  These attached themselves to all objects crystallizing in the most regular and beautiful manner. A blade of grass was thus converted into a pretty thick stalagmite some of the shrubs covered with spreading tufts of crystals looked as if they were in blossom while others more firmly incrusted might have passed for gigantic specimens of white coral.”

By January 5th  a “deep snow brought by an easterly wind had reduced the whole scenery to the more ordinary appearances of our winter”.  More snow followed on the 6th and piled into drifts on a strengthening NE’ly. The biting gusts presented Howard with yet another new winter phenomenon: snow rollers:  “With the temperature at the surface 33 or 34F presented an amusing phenomenon which was pointed out by my children. Instead of driving loose before the wind it was collected occasionally into a ball which rolled on, increasing till its weight stopped it. Thousands of these were to be seen lying in the fields some of them several inches in diameter”.

On the 9th Howard describes a misty morning and a snowy landscape that had a “bluish tint”. The “blueness” of the air is possibly down to the sheer cold – it was -13.3C that morning. I’ve seen something similar, a bluish hue to the air, on very cold mornings in the Alps. Howard notes that the minimum on the surface of the snow that night, the coldest of that winter, was -14.4C.

The River Lea close to where Luke Howard's laboratory stood by wanstead_meteo
The River Lea close to where Luke Howard’s laboratory stood

On the 11th a “very red” sunrise was observed . By the 12th Howard describes the Arctic scene from his laboratory: “The River Lea is now firmly frozen and the Thames so much encumbered with ice that navigation is scarcely practicable.” Howard also notes on this date that the snow in upper parts of Hampshire and “on the Hind Head” had fallen to a depth of 15 feet in places.

A slight thaw was noted on the 16th from the warmth of the earth. More snow fell on the 18th and 19th. Snow on the 20th was accompanied by a strong NE’ly. On the morning of the 21st Howard noted drifts “many feet deep”.

The 22nd to the 25th saw more outbreaks of snow before the wind swung into the SW on the 26th with snow followed by rain – the cold spell was beginning to lose its grip. Howard notes on the 29th: As the barometer began to rise the wind came round by SW to NW and blew with great violence till near morning”. Classic freeze/thaw conditions followed over the next few days before the real thaw, and the end of the frost fair, arrived on February 5th. Howard notes: “Crimson sky at sunrise hollow wind snow and sleet. 6th A gale from SW with showers of rain at evening.”

Sunset from Southwark Bridge overlooking St Paul's Cathedral by WansteadMeteoThe rest of February, and meteorological winter, appears fairly nondescript. Howard notes that on the 12th a gunpowder explosion resulting in a fire at the Custom House, 5 miles south, caused a  “shower of fragments of burnt paper”. Sharp frosts and misty mornings prevailed to end of month, Howard noting the “clear orange twilights”, probably caused by the eruptions in Italy that formed a new crater on Vesuvius. Howard mentions a letter he received from Heligoland on February 21 which had also seen intense frost that was preceded by thick fogs and heavy falls of snow. The latter was 10 and 12 feet deep – the frost lasting six weeks.

Howard wrote his own account of the frost fair…

“The Thames Frozen Over

January 15: The masses of ice and snow had accumulated in such quantities at London Bridge on the upper side yesterday that it was utterly impossible for barges or boats to pass up. During the whole of this week that part of the Thames below Windsor Bridge called Mill River has been frozen over and has been crowded with persons skaiting.

February 3: The confidence of the public in the safety of the passage over the frozen surface of the Thames was yesterday increased. All the avenues from Cheapside to the different stairs on the banks of the river were distinguished by large chalked boards announcing A safe footway over the River to Bankside and in consequence thousands of individuals were induced to go and witness so novel a spectacle and many hundreds had what we cannot help terming the fool hardiness to venture on the fragile plain and walk not alone over but from London to Blackfriars Bridge. Several booths formed of blankets and sail cloths and ornamented with streamers and various signs were also erected in the very centre of the river where the visitors could be accommodated with various luxuries. In one of the booths the entertaining spectacle of a sheep roasting was exhibited

February 7: Friday several printers brought presses and pulled off various impressions which they sold for a trifle eg Printed to commemorate a remarkably severe frost which commenced December 27, 1813, accompanied by an unusual thick fog that continued eight days and was succeeded by a tremendous fall of snow which prevented all communication with the Northern and Western Roads for several days. The Thames presented a complete field of ice between London and Blackfriars Bridges on Monday the 31st of January, 1814. A Fair is this day February 4, 1814, held and the whole space between the two Bridges covered with spectators. This field of ice was indeed a very rugged one consisting of 1 masses of drift ice of all shapes and sizes covered with snow and cemented together by the freezing of the intermediate surface. The deceitfulness of the latter caused as is too common on such occasions the loss of some lives by drowning. The following passage announcing the opening of the river soon after is worthy of preservation on account of the spirit in which it is written.

February 11: We are happy to see the lately perturbed bosom of Father Thames resume its former serenity. The busy oar is now plied with its wonted alacrity and the sons of Commerce are pursuing their avocations with redoubled energy. Cheerfulness is seated on the brow of the industrious labourer those who were reduced to receive alms as paupers again taste the sweets of that comparative independence with which labour crowns the efforts of the industrious. What a fruitful source of congratulation does this prospect afford nor can the contemplative mind dwell on the subject without feeling gratitude to that beneficent Being who in a time of such calamity opened the hearts of the benevolent to administer from their abundance to the necessities of their poorer brethren and thus add cement to the bond by which all mankind are linked together. The mischief done on the river during the late frost is greater than can be remembered by the oldest man living. Among the craft alone it is calculated to amount to upwards of 10,000 independent of the damage sustained by the cables tackle & of the shipping.”

 

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Wanstead Weather: 2013 review

The mean temperature of 10.7C makes 2013 0.5C colder than the 1981-2010 average. And makes the year 46th warmest in the series going back to 1881.
Rainfall of 554.9mm is 92% of average for a year in this area, making it the 68th wettest in the series back to 1888. Some areas of the British Isles have been considerable wetter – this just reflects how variable rainfall can be.
Though the year appears fairly average it masks some notable events…
A couple of notable falls of snow were observed in January and February
A couple of notable falls of snow were observed in January and February

January saw a couple of notable falls of snow, the first of which arrived on the 18th. By the morning of the 21st there was 13cm lying.

February saw a further snowy spell with 5cm falling on the 10th – but this only lasted a couple of days.
The mean temperature for March of 3.6C made it the coldest since 1892, the 3rd coldest in the series since 1881.
After a cool and dry spring and early summer July surprisingly turned out to be the warmest since 2006 – the mean temperature of 20.7C being the third warmest in the series going back to 1881. The warmest day of the year occurred on 22nd when 34C was recorded. This was followed by a very potent thunderstorm in the early hours of 23rd.
Autumn overlooking The Temple in Wanstead Park, by Wanstead Meteo
Autumn overlooking The Temple in Wanstead Park

An average August and September saw a couple of notable rainfall events with 32.8mm on 24/8 and 32.6mm on 13/9 being the the 27th and 28th highest 24hr totals in a series going back to 1961. In the August event Maldon in Essex saw in excess of 100mm leading to flooding. What made it more noticeable is that these events occurred during dry spells.

The end of October saw the St Jude storm blast through Wanstead. The strength of the gusts saw the demise of a few mature limes on Christchurch Green as well as trees in Wanstead Park.
So the stats…
Temperature (°C):
Mean (min+max)   10.7
Mean Minimum     6.7
Mean Maximum     14.7
Minimum          -7.0 day 16/01
Maximum          34.0 day 22/07
Highest Minimum  18.7 day 22/07
Lowest Maximum   -0.6 day 16/01
Air frosts       53
Sunset on Wanstead Flats by Wanstead Meteo
Sunset on Wanstead Flats

Rainfall (mm):

Total for year  554.9
Wettest day      32.8 day 24/08
Rain days        158
Wind (mph):
Highest Gust    47.2 day 28/10
Average Speed    2.9
Wind Run         25327.8 miles
Pressure (mb):
Maximum          1039.3 day 26/11
Minimum          974.9 day 23/12
Days with snow falling         25
Days with snow lying at 0900   12

Wanstead Weather – December 2013

Trees in fog by WansteadMeteo
The beginning of the month started with lots of calm, quiet weather with fog and night frosts. A high pressure inversion so not a proper ‘cold spell’

December was warmer than average with a mean temperature of 6.5C (0.9C above the 30-year average) – ranking it 33rd in the series since 1881. Rainfall of 81.9mm was 154% of average – ranking it 22nd in the series.

The month was 1C warmer than last December – with 84% of the rain that fell in December 2012.

Despite it ‘feeling’ like it has been the stormiest December for some years this month was not as windy as December 2012. To illustrate this the ‘wind run’ for this month (the number of revolutions of the anemometer) was 2408.7 miles. Last December was 2654.5 miles, in other words last December was 10% more windy.

Air frosts: 4

Ground frosts: 11

Thunder: 1

Small hail: 1

MetDesk rain radar for 23rd
The rain on the evening of the 23rd was heaviest to the south and west of us – with 75mm in the Warlingham area of Surrey. Flooding and high winds caused hundreds of thousands of power outs in Sussex and Kent

Instrument pioneers in a very different West End

There was a time when not too far from the hustle and bustle of Selfridges, Harvey Nicks and Fortnum & Mason stood a fine scientific instrument supplier.

This advert, in an old HMSO Observer's Handbook, gives a no-nonsense list of what you'll find at No.122 Regent Street
This advert, in an old HMSO Observer’s Handbook, gives a no-nonsense list of what you’ll find at No.122 Regent Street

Negretti & Zambra, at No. 122 Regent Street and later at No. 15 New Bond Street, specialised in barometers and thermometers – everything you could need to set up a weather station. The brand among weather anoraks is the byword for quality. The company, along with Short & Mason, probably made the majority of barometers that adorn many hallway walls across Britain. Next time you visit old aunt Flo or uncle Albert chances are the barometer hung on the wall is made by one of these companies.

Enrico Negretti and Joseph Zambra started their company in 1850, which was run by them and their descendents until well after the Second World War. They had shops firstly in Regent Street and later at Holborn Viaduct. The company was highly successful, winning a medal at the Great Exhibition in 1851, counting among their customers the Astronomer Royal, Prince Albert, the Royal Observatory and Admiral Robert Fitzroy.

Initially they specialised in barometers and thermometers, particularly those needed for taking deep sea and atmospheric measurements, which until they arrived were very unreliable. Later they increased their range to include telescopes, gun sights, theodolites and optical instruments. During the Second World War Negretti expanded substantially to meet the demand for instruments for war planes in particular. Their  instruments were also produced under licence to supply the USAAF.

After their stand against Nazism in World War II, the two men helped found the United Nations. Churchill’s mother was American and he and FDR were distant cousins
After their stand against Nazism in World War II, the two men helped found the United Nations. Churchill’s mother was American and he and FDR were distant cousins

Go to No.122 Regent Street today and you’ll find a branch of the Body Shop. The shop at No.15 New Bond Street, which closed in 1975, 11 years after the company moved production to a factory in Aylesbury, is now a branch of watchmaker Patek Philippe. Outside you will find seated bronze statues of Allied wartime leaders Sir Winston Churchill and Franklin D. Roosevelt sharing a joke. The statue by Lawrence Holofcener was unveiled in 1995 by the Bond Street Association to mark 50 years of peace. I’m not sure how intentional this was but how fitting that they are outside Negretti’s old shop, the instruments of which played a big part in helping the Allies to prevail over the Axis.

Back in the day N&Z was highly regarded in the local community and people would phone to access data that the company compiled from its rooftop weather station. In the late 1950s it was the job of Geoffrey John Gill, an office junior who went on to become an apprentice draftsman, to collect these stats.

“I was getting tea, coffee and buns from a Greek cafe in Soho’s Wardor Street for the office staff, collecting the mail and using the franking machine and last but not least the holy of holy’ climbing to the shop roof top and collecting the charts from the sunshine glass ball recorder, the rain gauge, barograph and the hygrometer box. You see it was common in those days for people to phone N&Z to enquire what these readings had been for the past day or so, a typical quality N&Z service.” A full account of his time with the company can be found here.

Short and Mason were based in Walthamstow for nearly 60 years. They supplied instruments to the Polar expeditions of Scott and Shackleton
Short and Mason were based in Walthamstow for nearly 60 years. They supplied instruments to the Polar expeditions of Scott and Shackleton

Short & Mason were established five years prior to Negretti in 1845 by Thomas Short and James Mason. The business was located at 40 Hatton Garden, London, and produced precision measuring instruments including barometers, anemometers, and compasses. They became leaders in the field of barograph design and supplied scientific instruments for the Scott and Shackleton polar expeditions in the early 20th century and for Everest climbers.

In 1910 the company relocated to Macdonald Road, Walthamstow. It was here that 11 years later the company pioneered the theory that a storm forecast could be made from just observing the air pressure and whether it was rising or falling. The company went on to develop aeronautical, medical, meteorological and surveying instruments and were listed exhibitors at the British Industries Fair in 1922 and 1947.

In 1958 the business moved to Wood Street, Walthamstow, where it continued to trade until a merger in 1969 with Taylor Instrument Companies, of Leighton Buzzard, Beds. An account of somebody with experience of working for Short and Mason can be found here.

Many examples of Negretti & Zambra and Short & Mason instruments can be found on eBay and antique shops across the world, the finer examples often turn up at auction houses such as Bonhams where they go for thousands of pounds.

Though, like many industries, weather observing has become mostly automated there are are still probably hundreds of observers who still take the manual measurements every morning ‘because they can’. Though this observer relies on an automatic weather station for daily readings – there is nothing like the daily ritual of emptying the Snowdon raingauge or shaking down the maximum thermometer at 0900 GMT every day. One observer who still supplied the Met Office with monthly rainfall readings while in his 80s said that it was the one thing that got him out of bed every morning.

Examples of Negretti & Zambra instruments can be found on eBay
Examples of Negretti & Zambra instruments can be found on eBay

Perhaps it’s a little similar to the ever growing popularity of classic cars. A sense of being able to hold a piece of British engineering history that was so well designed that it still works today.

Snow Survey of London (1946 – 2019)

I first wrote this blog in December 2013 not realising that the following winters were going to turn so mild. Winter 2013/14 ranks the worst of any winter I’ve studied in this area back to the snowy season of 1946/47. The following three winters ranked 53rd, 62nd and 42nd – the only ‘top 10’ winter for snowfall of the past 30 years was 2009/10!

Snow is a very rare commodity in lowland Great Britain – even rarer in the Home Counties, and in our part of east London. Pulling back the curtains on a cold winter’s morning to be greeted by a fresh fall of deep, crisp and even snow is something most children experience and hold dear for life. The slush, ice and chaos that inevitably follows all too quickly is forgotten.

OLYMPUS DIGITAL CAMERAMy memories of winters in the 1970s and 1980s is that they were far snowier and colder than they are today. But were they *always* cold and snowy? I decided to have a look back through the archives to find out. My first stop was the Met Office’s now defunct Snow Survey of Great Britain. This excellent compilation of reports logged by observers nationwide was printed annually as part of British Rainfall. But through lack of interest and cuts printing ceased after the 1991-92 season. Data continued to be collected though the modern version of the survey uses satellite technology to estimate daily UK snow depths – the spiel on the Met Office website tells us that this is far less subjective than an individual nipping out at 9am every morning to ‘stick in a ruler’ and, those within sight of high ground, to observe where the snow line is. Call me old fashioned but this is not very romantic and does a disservice to the hundreds of observers who down the years diligently logged all their information as objectively as possible. But on to the data…

Regional data was not included in the survey until the 1965-66 season. Though Wanstead isn’t listed I have taken an estimate from data supplied from stations at Eastcote (53m), East Barnet (70m), Charlton Park (46m), Twickenham (13m), Teddington (9m). Because this area is influenced by Thames streamer snowfall that blows in off the North Sea and is funnelled upriver I have also considered readings from Epping (107m), Rayleigh (73m) and Southend (27m). Indeed, in some years Wanstead’s snowfall is much more similar to Rayleigh and Southend than it is to Greenwich and Teddington. Though my site is only 18m it seems to catch the snow much better than surrounding areas – probably to do with the fact that Aldersbrook is surrounded by greenery. People walking down from Wanstead village often remark that Wanstead Park is far snowier than the village a couple of dozen metres or so higher. Before 1965 I have used data from Woburn, Bedfordshire, which at 89m and 40 miles away as the crow flies, is the closest station in that long running series.

The mean temperature of a winter can look cold but it doesn’t always tell the full story. You can have a winter dominated by high pressure over the near continent making things very dry. But the anticyclones that ridge from Central Europe to the Azores can leave us in the ‘warm’ part of the high – and often lead to days of anticyclonic gloom; cold grey, dank and boring weather with little sunshine. On paper a season can look cold but in reality totally unremarkable; it is the number of days with ‘snow lying’ that people remember. For snow to settle it needs to be cold! For this reason I haven’t bothered with ‘snow falling’ data as it can snow at 4C in very dry air – yet nothing settles. Most weather geeks find ‘snow falling’ the most frustrating when it doesn’t stick. So on to the results.

The Top 20 winters in Wanstead, using 'snow lying' and 'mean temperature' in stats. Click the image to view all 67 winters
The Top 20 winters in Wanstead, using ‘snow lying’ and ‘mean temperature’ in stats. Click here to view all 71 winters back to 1946/47

Once I worked out the ‘snow lying’ days I decided to devise a winter index by dividing ‘snow lying’ by seasonal mean temperature. Because the results using Celsius were problematic in that 1962/63 becomes very skewed upwards I decided to use Kelvin. The results are quite surprising. Coming out top, not surprisingly, is 1962-63 with an index of 25.2 and 69 days of snow lying. Second is 1946-47 with an index of 21.1. Third is 1981-82  with an index of 10.5 – surprisingly ahead of 1978/79, the first winter in the series that I can recall; I remember returning home from school one night in December 1978 and the snow being as deep as the twelve-inch step to our house.

The index of 25.2 for the 1962/63 winter and 21.1 for 1946/47 – over double the amount of 1981/82 – shows how ‘off the scale’ those two winters really were. My father, who doesn’t share my enthusiasm for the weather, can distinctly recall the severe conditions of 1962/63. He said the roads were so thick with snow that when the thaw finally arrived in March he’d become so used to driving on snow that he crashed through somebody’s front garden wall, after losing control of his Mini on surface water sat on the ice.

More recent winters, which pale by comparison, rank surprisingly highly. The 2009/10 winter comes in at Number 10, higher than the legendary 1986/87, where the coldest day in recent times was recorded in London, which came in at Number 12. It should be noted that January 1987, when on the 12th the temperature did not rise above -5.5C all day, was sandwiched by a mild December and February.

OLYMPUS DIGITAL CAMERASomebody asked me if it would snow and by how much over the next three months. The simple fact is I don’t know. While a predicted mean can look chilly on paper it is impossible to decipher how many peaks and troughs there will be. Just by looking at winters with a mean of, say, 5C doesn’t tell you much about snowfall. When you look at 1985-86 (mean 4.1C)  there were 22 days of snow lying at 9am – yet 2005/06 was colder (3.9C) and only 3 mornings saw snow lying – though that winter was particularly dry – the 13th driest in the series.

The median for ‘snow lying’ days in this series is six. The rolling median of the past 30 years, however, is only 2 so, with this in mind, if it does snow you should get out there and make the most of it.

You can view over 70 years of winters in this area, all ranked using my winter index here.

Screen Shot 2017-12-21 at 14.44.05

*It should be noted that a day of ‘snow lying’ only qualifies if there is more than 50% cover at the observation time of 9am. This means that it could snow 1cm at 10am – if that snow thaws by 9am the next day it won’t count. Though 8 winters appear snowless it is possible that these winters did see temporary coverings

Will it be a White Christmas this year?

Will it be a white Christmas this year? It’s the question most forecasters get asked year after year as the big day looms less than a month away.

The snow probably won't arrive until after Christmas this year
The snow probably won’t arrive until after Christmas this year

It always fascinates me why Christmas and snow are so closely associated with each other when the odds, especially in London, are so stacked against it happening.

Perhaps it is the Christmas card scenes of Dickensian winters that get people yearning for the white stuff. Indeed, the image of snow covered cobbled streets can probably be blamed on Charles Dickens. The backdrop of A Christmas Carol, and a host of other books, were written when winters, and Yuletide, were generally much colder than they are now. Perhaps it was also the cold Decembers, which came during notably cold years as he was coming of age, that sowed the seed of his impressions of life in London. The Central England Temperature (CET)  for December 1829 and 1830 were 1.4C and 1.8C respectively. To give you perspective the average mean temperature for the Wanstead region in December is 5.6C. Of course we had a taste of what a Dickensian December was like three years ago in 2010 when the average mean temperature was 1.5C. Though bear in mind the mean for 2010 was 10.5C – way above the 8.2C and 8.7C mean temps of 1829 and 1830!

Christmas toys of yesteryear also took every opportunity to perpetuate the snow myth
Christmas toys of yesteryear also took every opportunity to perpetuate the snow myth

But back to this Christmas… First of all, what do we mean by a white Christmas? The definition used most widely – notably by the bookies – is for a single snowflake, even if it lands in the midst of heavy rain, to be observed falling in the 24 hours of 25 December at a specified location recognised by the Met Office. Interestingly, the Met Office uses weather observations from Gravesend-Broadness, some 12 miles away, to show current conditions in Wanstead. A lot, however, could be said by us weather anoraks about the different microclimates between here and south of the Thames.

Technically, there has not been a white Christmas in Wanstead for over 30 years. In 2010, we could still see the Christmas card Victorian snow scene in small patches of our gardens, but these were leftovers of a previous dump, so it doesn’t count. Frustratingly, there has been snow on several Boxing Days in Wanstead (1995 and 1996) and in the weeks running up to Christmas, but not on Christmas day itself. The most typical Wanstead Christmas day weather is mild and dry, although it has rained on 12 of the last 33 Christmas days.

So why does it often snow either side of Christmas but not on the actual day? For Wanstead, Christmas is at the beginning of the period when it’s likely to snow. Looking at climate history, wintry weather is more likely between January and March than December.

iced anemOn average, snow or sleet falls in the UK 5 days in December, compared with 7.6 days in January, 6.8 days in February and 6 days in March. White Christmases were more frequent in the 18th and 19th centuries, even more so before the change of calendar in 1752, which effectively brought Christmas back by 12 days. Climate change has also brought higher average temperatures over land and sea and this generally reduces the chances of a white Christmas.

For snow to fall we need moisture in the atmosphere. Snowflakes start their lives as ice crystals thousands of feet up, and when these tiny ice crystals collide they stick together in clouds to become snowflakes. If enough ice crystals stick together, they’ll become heavy enough to fall to the ground.

Precipitation falls as snow when the air temperature is below 2°C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snowfalls tend to occur when the air temperature is between zero and 2°C. The falling snow does begin to melt as soon as the temperature rises above freezing, but as the melting process begins, the air around the snowflake is cooled. If the temperature is warmer than 2 °C then the snowflake will melt and fall as sleet rather than snow, and if it’s warmer still, it will be rain.

It sounds a simple combination, but getting precipitation on the days when there are temperatures low enough for snow are few and far between.

temple snowChristmas day in Wanstead, on the balance of probability and from previous patterns, is most likely to be a green and mostly cloudy but dry one. Some brightness is possible with temperature peaking at around 10°C. You can read my full methodology on why I think this may happen here.

Though my attempt to find the probability of a White Christmas effectively rules one out, there is still an outside chance that one could happen.

At this time of year the UK can effectively become a battleground between cold polar continental air to the north or east and moisture-laden mild tropical maritime air to the south and west. Where these air masses meet, snow is possible, but a lot depends on which air mass wins the battle. When battleground situations occur, in one location it can be snowing, but just 20 miles or so down the road it can be raining. This is because there is a fine line between the boundary of the warm and cold air.

There's nothing like an open coal fire. It's even better when it is cold enough outside to have one
There’s nothing like an open coal fire. It’s even better when it is cold enough outside to have one

In years gone by, Wanstead and the surrounding area has often ended up in the cold air mass or the warm air mass. In these situations dry and mild or dry and cold weather is often the result. Of course, in a cold air mass situation there is always the chance of showery activity of the North Sea. The weather so far this winter has not been anything out of the ordinary, so I’m afraid there is nothing to suggest a white Christmas is likely.

If it does turn very cold on December 24, pray for clouds to appear and we could be in with a chance. But at the end of the day we still need that vital combination of temperature and moisture. Snow, like Christmas in that sense, requires some magic.

Wanstead Weather – November 2013

Wanstead Weather – November 2013

November was colder than average with a mean temperature of 6.7C (1.2C below the 30-year average) – ranking it 69th in the series since 1881. Rainfall of 56.5mm was 99% of average – ranking it 61st in the series.

The month was just 0.04C cooler than last November – with 93% of the rain that fell in November 2012.

Air frosts: 4

Ground frosts: 9

Thunder: 1

Small hail: 1

Winter Forecast 2013/14 (with no apologies to the Daily Express)

Much has been printed in the tabloids over the past month or so that we are in for a severe winter. Not a week goes by without the Daily Express splashing that the ‘Worst winter EVER is on the way’. Just this morning the same rag told us that three months of ‘exceptionally cold’ weather are due. On closer inspection the story elaborated the scene with quotes from James Madden of Exacta Weather, one of the ‘experts’ feeding these fantastical stories.

The Temple, Wanstead Park, always looks that much more stunning with a covering of snow
The Temple, Wanstead Park, always looks that much more stunning with a covering of snow

Quite how Mr Madden and other experts arrive at these forecasts is a bit of a mystery. The mystery has deepened further since I decided to crunch a few numbers and try to predict what is in store for the months ahead. Looking at data for this area stretching back over 130 years to 1881 I decided to calculate a seasonal average and arrived at a final figure using singularities – basically looking at the weather patterns we’ve had during October and November.

Many professionals would scoff at this method of pattern-matching, so I’ve incorporated a couple of other ‘now’ factors and taken on board current variables such as sea surface temperatures in the Atlantic and Pacific.

The figure I arrived at, taken as an average of the closest matching autumn periods, is a mean temperature of 4C with rainfall totalling 133mm over the months of December, January and February – that’s about a degree colder than average and 90% of average rainfall. The probability of a winter with a mean temperature of between 4C and 5C is 37% – the most likely outcome. With this in mind a winter in the form of 1986-87 is possible – though whether we would see the same extremes of temperature and snowfall that we experienced in January 1987 is open to question.

Here is a link of my method to predict the coming winter.

The Met Office, with all their computing power and expertise, seem to be hinting at something similar – ie slightly colder than normal. The opening couple of weeks to my forecast seem quite plausible, looking at tonight’s models. Look at the similarity in the synoptic charts for December 8th here.

Shoulder of Mutton lake, Wanstead PArk
Shoulder of Mutton pond, Wanstead Park

Over the last few years the snow lovers among us have been spoiled after a run of very mild winters during the late Nineties and early Noughties that prompted climate expert Dr David Viner to utter the immortal words that one day “children just aren’t going to know what snow is”. It was only a matter of a few years before the words from the senior research scientist at the University of East Anglia seemed a bit hollow.

Mark Twain, born this day in 1835 , once uttered the famous phrase: “Climate is what we expect; weather is what we get” – there is always a chance we could suddenly lurch back to milder winters. This winter could spring a surprise, be it very cold or very mild. But judging what’s happened over the last 130-odd years – a 1962/63 or a balmy 1989/90 look very unlikely.

* Forecasting models use probability on any given outcome. Millions of observations are fed into the Met Office database (and other countries’ weather agencies) every day. Supercomputers then crunch through this data to give probable outcomes. With the volatility of the atmosphere it is not surprising that certainty of any outcome often falls away rapidly. Forecasting has improved greatly in the last 20 years – though anything the models churn out beyond three to five days should be handled with caution. Long range models can give *some* idea of general trends for the months ahead – but changing just one variable can vastly alter an outcome at the end of the run.

* *Over the past few months I have been collating data for the area around Wanstead. This data is freely available from the excellent Met Office library and is emailed via Excel spreadsheet. Rainfall stats include a near-complete daily archive, stretching from 1961 to 2003, from City of London Cemetery . Sadly the rainfall station, along with many others, ceased to supply the Met Office after cuts were made shortly after the turn of century. Prior to 1961 I have used monthly figures taken at the Greenwich Royal Observatory stretching back to 1881. Though this is 6 miles away the difference in temperature between the two areas would be miniscule compared with rainfall data and so can be used. I use my own stats for the period after 2003.

Wanstead Weather’s live twitter feed is a year old

imageThe Wanstead Weather live Twitter feed is one year old today. That’s over 8,700 tweets of hourly weather updates. In that time there’s been 59 air frosts, 632mm of rain, 165 rain days, 27 days with snow falling, 13 days with snow lying – a total of 14cm falling.

Highest max was 34C on July 22nd, lowest min was -7C on January 16th. A windrun of 25,741 miles shows that the anemometer has turned enough revolutions to have circumnavigated the globe, albeit at an average speed of 2.9mph.

Where’s Jack Frost?

It’s usually around this time of year that this area experiences its first air frosts – but a warm, wet October caused by an active Atlantic and a jet stream sitting close to us has meant that classic radiative cooling nights have been in very short supply. There’s been a couple of chilly nights – down to 2.6C on October 30th and November 5th – but to record an air frost the thermometer must read below 0 Celsius (32Fahrenheit).

The first frost last year was recorded on November 6th. Much hoar was seen around the shady banks of Shoulder of Mutton pond in Wanstead Park
The first frost last year was recorded on November 6th. Much hoar was seen around the shady banks of Shoulder of Mutton pond in Wanstead Park

Last year, Wanstead recorded its first air frost on November 6th (-1C). Looking back through the records to 1980 the earliest frost was October 17, 1992, and the latest was January 6th, 2004. Interestingly it appears that having frost in October can signal a mild winter to come!. The median for the first frost is November 16th – 18th. Forecasts for this week suggest we could be scraping the windscreens for the first time on Saturday, thanks to high pressure building in from the Atlantic and calming things down.

Indeed, the models today suggest there is a chance of a block forming in the Atlantic which effectively stops depressions from whistling in from the west, unlocking the door for cooler weather from the north or east. It’s a long way off in meteorological terms though.

Here is a list of first air frosts in Wanstead…

The ECMWF model shows high pressure riding in from the Azores at the end of the week
The ECMWF model shows high pressure ridging in from the Azores at the end of the week

2012: Nov 6th (-1C)

2011: Dec 17th (-0.3C)

2010: Nov 15th (-2.2C)

2009: Dec 15th (-0.2C)

2008: Oct 29th (-1.3C)

2007: Nov 16th (-0.9C)

2006: Dec 10th (-0.4C)

2005: Nov 14th (-0.1C)

2004: Nov 14th (-0.6C)

2003: Dec 8th (-0.5C)

2002: Jan 6th 2003 (-0.9C)

2001: Dec 14th (-1C)

2000: Nov 15th (-0.3C)

1999: Dec 19th (-1.8C)

1998: Nov 22nd (-3C)

1997: Oct 29th (-1.5C)

1996: Nov 11th (-0.4C)

1995: Nov 18th (-0.1C)

1994: Dec 15th (-2.5C)

1993: Nov 16th (-1.3C)

1992: Oct 17th (-0.9C)

1991:Nov 10th (-0.4C)

1990: Dec 5th (-0.5C)

1989: Nov 24th (-2.4C)

1988: Nov 6th (-2C)

1987: Oct 25th (-2C)

1986: Dec 7th (-0.5C)

1985: Nov 3rd (-5C)

1984: Dec 11th (-3.4C)

1983: Oct 23rd (-1.1)

1982: Nov 29th (-2.6C)

1981: Dec 8th (-0.5C)

1980: Dec 1st (-3C)