Category Archives: UK snowfall

The year snow fell in London in October

Two hundred years ago this October the extremely rare phenomenon of lying snow in October was recorded in London.

A likely plunge of Arctic air on the 21st saw rain turn to snow which lay nearly 8cm deep by the morning and remained for nearly a week.

The month started dry and warm. On the 1st Luke Howard recorded 75°F at his laboratory in Stratford. The warmth remained into the second week with 77°F recorded on the 10th, 11th and 12th.

oct 1819
The values from Luke Howard’s Climate of London.

The wind swung into the north on the 18th and with it arrived the first hoar frosts that were cold enough to kill garden plants.

On the 21st the cold air further dug in and with it rain that turned to sleet. Howard said: “It began to snow about noon falling in very large flakes thick and rapidly for an hour and covering the ground. Some rain followed.

“In the evening the wind rose and it blew hard in the night from NNW. At midnight came a second heavy fall of snow which continued till 6am and though at first much of it melted it lay in the morning a full three inches deep.”

Howard adds that the surroundings ‘took on appearance of mid winter with the single exception of the foliage still remaining on the trees which mingled with an enormous burden of snow presented a very singular and grotesque appearance’.

The weight of the snow was also enough to break off large limbs from fruit trees.

The snow was still lying on the 23rd and, probably caught out by the earliness of the polar plunge, swallows were seen at Stamford Hill. On the 24th a very white frost was observed with a low of 31°F recorded at Tottenham.

More wintry weather followed in November, December and January.

Could snow fall here again in October? The probability is very low but it is not impossible, given the right synoptic conditions. Recent cases of notably positive and negative anomalies following in quick succession somewhat mirror the weather of Howard’s day.

 

 

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January 2019: rather cold, dry

January was most notable for being on the cold side, in contrast to December.

The mean temperature finished 4.1C, 1.1C below average, over 2C colder than last January.

Some 32.9mm of precipitation was recorded, 62 per cent of the 1981-2010 average, about half what fell last year, the driest January since 2006

Some 55 hours of sunshine were recorded, that’s 109 per cent of average, sunnier than last year.

Fourteen air frosts were recorded.

There were four days where snow fell but only one day of snow lying, 1cm on 23rd.

To view full stats follow this link:http://1drv.ms/1kiTuzv

My winter forecast went a bit awry in December – I predicted a mean of +0.8C, the outcome was +1.7C. January has been much better, I predicted -1.2C, the outcome is -1.1C! Also… “And another cold spell end of January into the first week of February?”
For February I predicted a mean of -1.7C. The current pattern to continue and signs on the EC of a more robust cold spell with air supplied by a Scandinavian high?

Halfway through winter: where’s the snow (again)

Five years ago I blogged about the lack of snow at the midway point through winter. This winter there has been a similar total lack of snowfall though this time it is benign anticyclonic conditions that have characterised the past 45 days rather than the raging zonality of the winter of 2013/14 which ended completely snowless in this area.

A look at the statistics reveals that the midway point of winter is the mildest for 3 years and the 6th mildest since 1960. There has also been around half the rainfall that we had to this point in 2018. Sunshine is similar and below average.

Since December 1st, Wanstead has recorded just 7 air frosts – 5 fewer than last year. The coldest night was just -2.5C. The current mean temperature this winter to January 14th is 6.9C with rainfall 60.6mm.

Further scrutiny of stats for the Wanstead area reveal few years were similar to this winter. Using my method for finding patterns stretching back over 50 years to forecast this winter I picked out years that were +/- 10% of the 2018/19 rainfall total. From these I then weeded out the seasons where the mean was within +/- 10% of the this year. This gave a list of three winters with similar temperature and rainfall.

50%

The other winters weren’t anything special with ‘snow lying’ days below the median for this area of six.

nevis
Snow go: just patches of snow were visible on the upper runs of Nevis Range at the weekend on Jan 12th

As I write there are signs that the weather is going to turn colder this week. Whether it will be cold enough for snow remains to be seen though the ECM model is hinting at a rise in pressure around Greenland. A situation that *could* be conducive for something colder long term.

In summary, the probability at this point of at least one fall of snow before the end of February could be put at 100 per cent. Whether it will be abundant or merely a dusting is impossible to tell.

Elsewhere in the UK it has been similarly lacking in snow. During a visit to Fort William at the weekend locals told me that there has been no significant snow since October / November and that even frosts were few and far between. The lifts around Nevis Range looked forlorn against a green backdrop. And it wasn’t until I got to the summit of Ben Nevis and Aonach Mor that I saw any of the white stuff.

 

 

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

 

 

Heading for a 1984/85 style winter?

With talk of an imminent statospheric sudden warming (SSW) I thought it would be interesting to have a look back at previous SSWs and see what precedents could be found.

December so far is showing similarities with 1984: mean maxima is within 0.3C of 1984 while rainfall is virtually the same at around 30mm!

During the winter of 1984-85 the polar vortex split on January 2nd, setting up that month to be among the coldest of the 20th century, on a par with 1979 and 1987. A more recent January that was just as cold was 2010.

Indeed, the winter of 1984-85 was among the snowiest of the past 70 years, ranking at number 5 in my survey of winters.

1984-2018.PNG

een

London winter forecast 2018-19

Long range modelled forecasts have been all over the place of late and, looking at the underlying signals, it is easy to see why.

When I’ve produced these forecast in the past, in terms of QBO and ENSO data, there’s usually a lot of analogues to compare with. This year, however, seems to be an exception.

Considering QBO first I looked back over data to 1950 and found nothing similar for October. However, looking over the whole series the cyclical nature of this circulation may give some clue.

bestfit

Some 20 months were revealed, ranging from June 1959 to June 2015.  Using NOAA’s  Niño 3.4 region I narrowed this list down to the few that had an ENSO value of around +1 with a rising trend. With NOAA’s forecast of a Modoki El Nino (one that occurs in the central Pacific) this narrowed the list to just 1 period: June 2015. Considering maxima anomalies this would give the following winter.

winter 2018-19 max anomaly.PNG

The above would suggest there being a general cool down through December with a cold spell starting just before Christmas into the new year? And another cold spell end of January into the first week of February?

winter 2018-19 precip anomaly

The above precipitation anomaly chart would suggest a wetter than average December,  January and February, though February by much less so.

It’s been a very busy autumn so I’m keeping this short.

The below figures, particularly January and February, may be different in the event of an SSW occurring. In all then.

The mean:
December: +0.8C
January: -1.2C
February: -1.7C
Overall: -0.3C (broadly average)

Precipitation:
December: 158%
January: 155%
February: 120%
Overall: 134%

 

March 2018: cold, some snow and very dull

Though March is usually, meteorologically speaking, the first month of spring this year it felt more like an extension of winter.

Screen Shot 2018-04-01 at 11.09.47
This graph shows that the two visits from the “Beast From The East” were only enough to momentarily dent the average.

The mean temperature for March 2018 finished 6.3C, that’s 1.4C below the 1981-2010 average, the coldest for five years but still nearly 3C warmer than the exceptional March of 2013.

Some 61.5mm of precipitation fell, that’s 151 per cent% of average and the wettest for 10 years, pipping the wet March of 2016 by just 1.2mm. The 38th= wettest March since 1797.

 

Screen Shot 2018-04-01 at 11.17.13
The wet end to the month is shown on this graph.

Perhaps most notable in this region was the lack of sunshine. There was just 59.1hrs recorded, that’s just 54 per cent of the 1981-2010 average. The dullest March since 1984 and, more notably, the 5th dullest March back to 1881!
Though there were no notable night frosts, the coldest night fell to just -3.8C, the cold pattern was enough to create three new entries in the top 10 of coldest March days in Wanstead and further afield in the capital.
With 6 more days of ‘snow lying at 9am’ winter 2017-18, the snowfall season stretches from October to May, was boosted up to 20th place on my snow index.
Summary for March 2018
Temperature (°C):
Mean (1 minute)  6.1
Mean (min+max)   6.3
Mean Minimum     3.0
Mean Maximum     9.6
Minimum          -3.8 day 01
Maximum          15.3 day 27
Highest Minimum  8.0 day 15
Lowest Maximum   0.5 day 01
Air frosts       5
Rainfall (mm):
Total for month  61.5
Wettest day      9.0 day 30
High rain rate   12.1 day 12
Rain days        20
Dry days         11
Wind (mph):
Highest Gust     24.4 day 08
Average Speed    3.2
Wind Run         2411.5 miles
Gale days        0
Pressure (mb):
Maximum          1032.3 day 20
Minimum          983.3 day 11
Days with snow falling         4
Days with snow lying at 0900   6
Total hours of sunshine        59.1
snow mar 1
19th march snowmar 3 tree eng thawmar 3 thawmar 2 snowmar 2 roadsmar 1 rada

‘So much for global warming…’

Since notably cold weather struck at the end of February I’ve lost count of the number of times I’ve heard this phrase uttered by the public and some sections of the press.

Top 20 cold
Top 20 cold anomalies

The ‘Beast from the East’ (versions 1.0 and 2.0) really captured the imagination in an age where everything has to have a label slapped on it; any message that these cold spells are ‘weather’ and not ‘climate’ seems to get lost.

Both spells, indeed the general pattern of our late winter weather, were driven by the stratospheric sudden warming event that lead to a split polar vortex in February – leading to a very cold end to the month and a mean temperature anomaly of -2.5C, the greatest monthly anomaly since March 2013.

To put it into perspective, however, it was nothing like some of the anomalies that occurred in the early 19th century: January 1814, for example, saw a monthly anomaly of -8.2C and coincided with the last occasion a frost fair was held on the Thames. Januaries back then were generally very cold, the 1801-1831 average monthly mean was -3C, that’s 8C colder than the most recent 1981-2010 average!

So climate now is much warmer but that is not to say that anomalously cold months can’t happen. February 1986 saw an anomaly of -5.6C, the 13th= greatest cold anomaly in my local dataset going back to 1797.

top 20 warm
Top 20 warm anomalies

The cold December of 2010 recorded an anomaly of -4.2C, 76th= greatest cold anomaly, while anomalies of -4.1C recorded in January 1979 and March 2013 were 77th=.

With the warming climate it is no surprise that most warm months happened very recently. The balmy month of December 2015  saw a positive anomaly of 5.4C.

The ‘Beast from the East 2.0’ was caused by a narrow tongue of extremely cold air from Russia scoring a direct hit on the UK. The odds of this happening must have been low but it is an example of how, when the synoptics of the atmosphere line up perfectly, anything is possible.

And it is an example how even in a warming climate the UK can still be subject to anomalous cold and warmth at any time of the year.

As the author Mark Twain reportedly once said: “The climate is what you expect; the weather is what you get.”

gfs
The upper air anomaly of the ‘Beast from the East 2.0’. 

anom
This graphic shows positive and negative monthly anomalies since 1797 against a generally warming climate

Because the above graphic is crowded I created one of anomalies since 1970. The upward trend is the same.

1970

march 1st

Repeat of March 24th 2013 only 10C colder

The weather this coming weekend reminds me of a March weekend in 2013 when large parts of the south-east woke up to a covering of snow.

Conditions in Wanstead were very knife-edge, the cover being very slushy. I remember going for a bike ride on that Sunday morning. We left Aldersbrook in sleet, the cover grew thicker as we pedalled into Essex. By the time we reached High Beach near Epping there was 8cm of fresh cover. Conditions on the 2-hour plus ride were inclement to say the least – the temperature didn’t rise above 0C!

This weekend we have a similar set-up, only this time the upper air at 5,000ft is a good 10C colder – no knife-edges this time and, if the streamer gets going, many places should see 10cm of cover. Don’t put away that sledge just yet!

 

Beast MkII or just a late March cold spell?

After the severe spell at the end of February that lasted into this month there’s lots of excitement / dread (*delete as appropriate) that the synoptic conditions that brought very cold air from our east is about to return.

The latest run on the GFS model shows that very cold air (-10C at 5,000ft) could be over us by next Sunday, with the ECM 12Z operational looking particular cold. ec

Snow this late in the year is very rare in the London area though, if the conditions are right, a blizzard is not impossible, as happened during the spring of 1952 when a two-day blizzard at the end of March brought drifts up to 6ft deep in the Chilterns.

Much more likely will be severe, possibly record breaking frosts. The coldest March night since 1959 across the London area occurred on the 3rd in 1965 with -7.4C recorded at Heathrow. Central London fell to -5C on the same night.

A look back at cold spells in March reveals that while snow was very scarce in London and the Home Counties it can be common on high ground from the Peak District northwards.

A history of March cold

1812: Luke Howard in The Climate of London noted that “great inclemency of the weather” on the 21st March disrupted mail deliveries between the north of Scotland and  Carlisle. The road between Appleby and Brough was impassable because of snow and between Sheffield and Manchester and Bradford and Halifax the snow had drifted from “two to three yards deep”.

Mail deliveries were also disrupted across South Wales.
In Plymouth a “a most tremendous gale from SW the whole of last night and this morning” brought flooding.
Howard’s account would confirm a classic battleground scenario of mild Atlantic air from the south pushing against cold Polar continental air in the north.
His own records from Stratford show a couple of cold days from the 16th, highs never lower than 2C, the coldest night on the 24th, being -4.4C. On the 20th he mentions snow in the morning followed by rain.
Wanstead mean: 4.9C (-2.8C) rainfall: 74.4mm (183%)

The following accounts of cold spells in March are recorded on the site London Weather.

1962: The first ‘spring’ month was colder than any month during the preceding winter. Frosty nights were much more frequent than normal, and sleet or snow fell on 10 days, although amounts were often trivial . On the 5th, the maximum temperature was only 2.2 C. Towards the end of the month, north to northeast winds were replaced by somewhat, cloudier milder, and moister south-westerlies. Atlantic fronts brought rain bands, and on the 29th nearly 10mm was measured.
Wanstead mean: 3.3C (-4.4C) rainfall: 36.5mm (90%) sun: 95.4hrs (88%)

1964: The first week of March was mostly cold with wintry showers and a fresh northeast wind. The temperature on the 7th only reached 2.3C. The second week was changeable and milder, and the high on the 13th was near 14C., but on the 15th, rain turned to sleet and gave a total of 26mm as cold air slowly encroached from the east. Nearly 15mm of rain fell on the 19th as milder air returned, but the rest of the month stayed mostly rather cold and changeable.
Wanstead mean: 4.9C (-2.8C) rainfall: 80.4mm (90%) sun: 63.5hrs (58%)

1969: The first week was mainly dry, and although dull and cold at first, it became fairly sunny and milder but with severe frosts. Overnight on the 6th/7th the minimum temperature was close to minus 8C. During the second week it became dull and wet, but after a cold start temperatures rose above average. Cold north-easterlies returned on the 16th with a high of only 3C., and cloudy, rather cold, and often wet, weather persisted until westerlies returned on the 29th.
Wanstead mean: 4.6C (-3.1C) rainfall: 53.2mm (131%) sun: 55.8hrs (51%)

1979: The first 12 days of March were changeable and windy with temperatures mostly above average. A wave depression formed on a cold front and produced 23mm of rain on the 13th, and as this depression became slow moving to the east of the country the rain turned to sleet and snow on the 14th, and continued into the 15th and 16th with highs near 3C. After mid month, the weather became less unsettled and milder, and the high on the 25th was near 15C.
Wanstead mean: 5.8C (-1.9C) rainfall: 96.5mm (237%) sun: 100.5hrs (92%)

1985: After a changeable start to the month, pressure built, and it became mostly dry, although often rather cloudy, with temperatures close to normal. On the 15th, showery rain turned to snow during the morning, and several cold and unsettled days followed. Sleet or snow fell on 5 days, and on the 21st the temperature failed to rise above 5C. Sharp frosts occurred, and although it then became less cold, the 26th was a miserable day with 11m of rain falling.
Wanstead mean: 5.9C (-1.8C) rainfall: 44.1mm (108%) sun: 100.5hrs (87.4%)