‘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

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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%)

Winter 2017/18 forecast review

At the beginning of December the opening par for my forecast for winter read:

The mean temperature for winter 2017/18 is looking average overall with average precipitation. While that doesn’t sound exciting for anyone looking for colder weather and snow I think the figures mask frequent 3 or 4 day-long cold snaps from the Arctic interspersed with milder interludes from Atlantic incursions; typical characteristics of a pattern driven by the troposphere. For anything longer term we have to hope for a warming of the stratosphere, a sudden stratospheric warming over the Arctic, that downwells into the troposphere, reversing the general westerly circulation. We are overdue an ‘SSW’ event but, even if one were to happen, its effects wouldn’t be felt until much later in the winter.

Figures generated using QBO statistics in the run up to December were identical to the outcome of 5C. It is figures generated using ENSO statistics, however, that produced the best results considering December, January and February alone.

It would seem that the winter was most influenced by the ENSO variable up until February when the effects of the SSW were enough to overcome it?results

 

 

Winter 2017/18: 27th out of 72

A few years ago I devised a winter index to try to decipher how modern winters ranked against legendary seasons, such as 1947 and 1963.

With the media hyping conditions last week, which were severe in many parts of the country, it is very difficult for many to gauge just how conditions compare with previous winters.

My findings show that this winter so far stands 27th. It is possible that further snowfall that results in lying snow at 9am between now and April will boost the position higher though, given recent years, this would seem unlikely.

index

Last week’s cold spell, while containing some impressive statistics, is put into perspective when it is compared with other severe spells since 1960. A decent cold spell but no record breaker in the form of a 1962/63.

Perhaps it is the advent of social media, the plethora of constant updates of the latest feet-deep snowdrifts and instant tales of heroism in the face of icy adversity, that has made this cold spell seem far more severe than it actually was in the minds of many; February / March 2018 was the first truly social media-driven cold spell.

Winter 2017/18: average, cold start and end

The winter of 2017/18 will probably be remembered as much colder that it actually was – the exceptionally severe spell right at the end was only at its halfway point by the time the meteorological winter was over.

pathfinder
Like a scene from the Pathfinder movie

The mean temperature for the season finished 5C, that’s 0.5C below average and the coldest for five years.

Rainfall was above average: 180.8mm fell, that’s 124 per cent of average and the wettest for four years.

Sunshine was just over average: 174.4 hrs is 104 per cent over average and the sunniest for tree years.

As so often with winters at this latitude the average for three months makes it look a non-descript season – it is only when you look at the detail that compelling facts emerge.

The coldest day of the season occurred on the last day of February when the maximum failed to rise above -1C, the first ‘ice day’ for five years and the coldest day since 2010. It was also the seventh equal coldest February day in a local record going back to 1959.

perch
Perch pond, being deeper, took longer to ice over

The coldest night of the winter was in the early hours of the 28th when a low of -6.9C was recorded. The temperature would have been far lower were it not for a shower that moved in at 3am.

The warmest day of the winter occurred on December 30th with 14.2C recorded. The warmest night was on January 28th when the temperature fell to just 10.8C.
The wettest day of the winter occurred on January 2nd when 15.3mm was recorded.

Snow arrived at the start of winter and at the very end: seven days of snow falling and four days of snow lying over the three months is below average.

 

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Screen Shot 2018-03-04 at 23.14.20
The daily mean temp yo-yo’d throughout December, January and February

There were 30 air frosts during the three months, eight above the 1981-2010 average.

air frosts

There were 11,680 minutes of frost over the winter, less than last year, though 66 per cent of those were recorded in February. Considering the past 6 Februaries this year’s frost hours were 170 per cent greater than the next highest, February 2016!.

frost minutes

A full weather diary is available for the months of DecemberJanuary and February. To view full stats for each month follow this link:http://1drv.ms/1kiTuzv

Summary for period 01/12/2017 to 28/02/2018

Temperature (°C):
Mean (1 minute) 5.2
Mean (min+max) 5.0
Mean Minimum 2.0
Mean Maximum 8.0
Minimum -6.9 on 27/02/2018
Maximum 14.2 on 30/12/2017
Highest Minimum 10.8 on 28/01/2018
Lowest Maximum -1.0 on 28/02/2018
Air frosts 30

Rainfall (mm):
Total for period 182.2
Wettest day 15.3 on 02/01/2018
High rain rate 28.2 day 02/01/2018
Rain days 52
Dry days 38

Wind (mph):
Highest Gust 45.0 on 02/01/2018
Average Speed 3.7
Wind Run 8059.5 miles
Gale days 0

Pressure (mb):
Maximum 1036.4 on 22/12/2017
Minimum 970.3 on 10/12/2017

Days with snow falling 7
Days with snow lying at 0900 4

 

 

February 2018: cold, very sunny, snowy end

February 2018 saw the start of the first decent cold spell since 2013 with thick (by modern standards) snow cover, deep cold air and bitter winds.

Screen Shot 2018-03-03 at 15.50.35
February 2018 is marked by the steady downhill temperature trend from the 18th.

It was the coldest February since 1991, the mean temperature of 2.8C was just over 2.5C below average. The month was ‘cold’ though it was the 19th onwards that really dragged the value down.

Precipitation was just below average; just over 34mm is 87% of average.

It was a sunny month, the sunniest February since 2012 and the 12 sunniest in a local record going back to 1881. Some 87.9 hours were recorded, 120% of average. Of that top 12, eight have occurred since 1988! A mix of changes in weather patterns, industry and council action?

Air frosts: 16. Ground frosts: 19. Snow falling: 6 days. Snow lying: 3 days (greatest depth 8cm 28th)

Full stats for February here: http://1drv.ms/1rSfT7Y

settled snow 28th
The 28th dawned sunny with fresh snowfall after an hour long shower at 3am. Within hours more showers moved in.