Category Archives: Weather

September 2019: wettest since 2006

Most of the rain of September 2019 fell in the last week making what was a fairly unremarkable month weatherwise the wettest September for 13 years.

Some 63.9mm of rain fell which is 123 per cent of average.

The monthly mean finished 15.8C, that’s 0.4C above average, the warmest September for 3 years, 0.6C warmer than last year.

Sunshine, at 150.5hrs, 107 per cent of average but over 30 hours fewer than last year.

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

sept

Summary for September 2019

Temperature (°C):
Mean (1 minute)  15.5
Mean (min+max)   15.8
Mean Minimum     11.1
Mean Maximum     20.5
Minimum          5.2 day 17
Maximum          26.0 day 15
Highest Minimum  15.7 day 23
Lowest Maximum   16.1 day 09
Air frosts       0
Rainfall (mm):
Total for month  63.9
Wettest day      14.9 day 24
High rain rate   28.2 day 27
Rain days        14
Dry days         16
Wind (mph):
Highest Gust     23.5 day 27
Average Speed    2.5
Wind Run         1809.2 miles
Gale days        0
Pressure (mb):
Maximum          1036.8 day 13
Minimum          992.3 day 29
Days with snow falling         0
Days with snow lying at 0900   0
Total hours of sunshine        0.0
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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.

 

 

Collapse of the Weisshorn glacier in 1819

Two hundred years ago this December a huge part of the Weisshorn glacier in Switzerland crashed down several thousand feet to the valley below.

saas fee glacier
A glacier above the village of Saas Grund, Switzerland. Viewed from below I am always struck by how precarious they look.

At 6am on December 27th 1819 the villagers of Randa, near Zermatt, were awoken as millions of tonnes of snow and ice swept away boulders, rocks, gravel and mature larch trees. Though the debris missed the village the force of the slide created a blast of air that moved entire buildings and their contents, burying 12 people, all but two of whom escaped with their lives.

Eyewitnesses described the noise of the falling mass as the loudest thunder and said a bright flash accompanied the slide before darkness once again enveloped the village.

First light revealed the utter devastation of the avalanche that have covered an area of pasture 2,400ft by 1,000ft by 150ft high.

It was not the first avalanche to bring disaster to Randa. In 1636 the village was destroyed by a similar avalanche when 36 people were killed. It is said that that occasion saw a much greater chunk of the flacier fall from the slopes of the mountain, at 14,783ft the 5th highest in the Alps.

Two other less serious falls happened in 1736 and 1786 but not precisely in the same place. This time only a small part of the glacier fell down.

Could a similar disaster happen again? With climate change and the nature of the Alps being constantly on the move it is possible. Earlier this month it was reported that part of a glacier on the Mont Blanc Massif, just 40 miles away as the crow flies, was on the brink of collapse.

I don’t have local figures but a look at the recent climatology in London shows that anomalies during the past couple of years – warmer than average summers and low rainfall – have been similar to what happened in 1819.

summer mean

summer rainfall

Of course the difference between now and 1819 is that we have early warning systems in place that can help prevent loss of human life in the event of a catastrophic avalanche.

weisshorn
The Weisshorn in the far distance seen from the slopes above Grächen

August 2019: warmest for 4 years

Apart from the hot four days in the last week August 2019 was fairly unremarkable.

Overall the monthly mean finished 19.9C, that’s 1.4C above average.

Rainfall at 37.7mm, was 75 per cent of average,  the driest for 3 years. Sunshine, at 180hrs, the sunniest for 3 years.

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

august max

Summary for August 2019:

Temperature (°C):

Mean (1 minute)  18.9
Mean (min+max)   19.3
Mean Minimum     13.9
Mean Maximum     24.7
Minimum          8.8 day 20
Maximum          32.6 day 27
Highest Minimum  19.5 day 07
Lowest Maximum   17.9 day 14
Air frosts       0
Rainfall (mm):
Total for month  37.7
Wettest day      12.6 day 14
High rain rate   65.8 day 09
Rain days        11
Dry days         20
Wind (mph):
Highest Gust     22.1 day 10
Average Speed    2.6
Wind Run         1941.4 miles
Gale days        0
Pressure (mb):
Maximum
Minimum
Days with snow falling         0
Days with snow lying at 0900   0

Two Paris heatwaves two centuries apart

In July 1808 Paris wilted in a heatwave. The average maximum for the 13-day spell that began on the 10th was 31°C, higher than a similar spell last month that saw the all-time record for the French capital broken.

The temperature at the peak of last month’s hot spell reached 42.6°C, some 6.4°C higher than the peak of the 1808 spell but, as the graph below shows, maxima fell back more quickly than 1808.

paris heat line

The more ‘pointed’ nature of maximum temperature during the spell last month backs up findings of the changing jet stream;  the wriggly nature amplifying the heat.

Tmin

mean

The average mean and minimum temperature of both spells showed a difference of just 0.2°C.

Since Paris recorded its hottest day ever there have been just two days where the temperature has exceeded 30°C.

paris july 1808
The values for the 1808 spell were listed in Luke Howard’s Climate of London.

The heat in Paris in 1808, like in 2019, was also felt in London. Luke Howard noted the following in The Climate of London.

“Very hot from July 12th to 19th. On the 12th a thermometer in perfect shade in a window in St James’s Park was 81.5 degrees at 3pm, and on the 13th at the same hour, 94 degrees. On the same day four men and seven women were killed by sunstroke in various parts of the Midland counties, and numerous coach and other horses were also killed. On the 15th a very violent and destructive thunderstorm in Gloucestershire, Monmouthshire, and surrounding counties.”

* Values for 2019 were taken from the station Montsouris.
** Though there is no way of knowing how accurate the 1808 values were previous studies have found that historic temperatures can be as much as 3°F too high.

July 2019: a new Tmax record

July 2019 saw the month’s daily maximum record broken on the 25th with a high of 36.8C, The reading beat the previous record set on July 1st 2015 by 0.8C and was the second highest reading recorded in this area. Cloud that drifted in mid afternoon put paid to any chance of all-time record though Cambridge, further north, managed to break the UK record with a reading of 38.7C. This temperature set in the Botanic Gardens beat the previous record of 38.5C set in Brogdale, Kent, in 2003.

 

north
The weather enclosure in the Cambridge Botanic Gardens meets WMO guidelines

Although it has been mentioned that the Cambridge site appears to be overdeveloped it meets the WMO standard and the Met Office are happy with the record.

Compared with 2003 the heat this time was far more widespread and further north, with many stations recording higher values than 2003, as shown by these 24 hours to 6pm readings below.

 

In 2003 some 44 stations recorded 30C or above whereas this year some 67 reached 30C or higher.

Though the heat was record breaking it was much shorter lived than 2003. Like last month and July 2015 the 9-day temperature trace is far more ‘pointed’ – perhaps a symptom of the changing behaviour of the jet stream.

Overall the monthly mean finished 19.9C, that’s 1.4C above average though 1.8C cooler than last July – the warmest month on record.

Rainfall at 61.5mm, was 141 per cent of average,  the wettest for 2 years. Sunshine, at 165hrs, is 85 per cent of average and well down on last July’s 273hrs.

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

2019july
‘Feels like’ maxima.
juky feels
June 1981-2019 maximum anomalies
july all.PNG

 

The 12 month rolling rainfall total is…

Summary for July 2019

Temperature (°C):
Mean (1 minute)  19.8
Mean (min+max)   19.9
Mean Minimum     14.7
Mean Maximum     25.1
Minimum          9.2 day 03
Maximum          36.8 day 25
Highest Minimum  19.6 day 23
Lowest Maximum   19.5 day 27
Air frosts       0
Rainfall (mm):
Total for month  61.5
Wettest day      20.6 day 19
High rain rate   16.1 day 18
Rain days        10
Dry days         21
Wind (mph):
Highest Gust     16.8 day 20
Average Speed    2.2
Wind Run         1664.1 miles
Gale days        0
Pressure (mb):
Maximum          1029.0 day 03
Minimum          1004.8 day 30
Days with snow falling         0
Days with snow lying at 0900   0
Total hours of sunshine        0.0

The night London slept out in the heatwave

Sleeping in heatwaves is never a great prospect even in an age where fans and air conditioning units are becoming more and more common.

In 1948, however, residents of Kensington and other areas of London were so hot and desperate to escape oven-like houses caused by temperatures well into the 90s that they decamped en masse into the streets and local parks to get some kip.

A report published in the Aberdeen Journal on Friday 30th July describes how folk down south were coping with the heat.

“The metropolis last night was like a large restless household—with all the lights ablaze, doors and windows thrown open, the family fretful, and endless pots of tea brewing far into this morning.

aspro heatwave ad Yorkshire Post and Leeds Intelligencer - Wednesday 13 August 1947“Perhaps one in ten among the 8,000,000 of us slept after midnight. For the rest, we tossed and turned and saw out this heatwave night, when temperatures were never below 71 degrees, a variety of ways. About midnight I walked past the gaunt old Edwardian mansions in Kensington. With the exception the lights that burned from every window, the scene was reminiscent of the early days of the Blitz.

“Families trekked across the roadway in varying stages of undress to their little bits of ornamental gardens. With them went camp beds, bed linen, umbrellas, “in case,” the children, and the household pets, choose a cool open-air camping spot and feel wonderfully adventurous and spartan in the process.”

“At regular intervals the adolescent members of the squatting colonies were dispatched to the tea and coffee stalls on the corner, and perhaps for the first time in years these traders ran out of stocks. On the Kensington-Chelsea boundary, where life becomes noticeably less inhibited and on occasions less swish, a mixed group of young artists was sleeping on the pavement off Fulham Road.

“Round the next corner, where many theatrical and film stars live, several had slung hammocks on their meagre front lawns – one actually suspended between the bathroom windows of two adjacent houses. Midnight street wear for both sexes was cool if unconventional —silk pyjamas, bath robes, tennis shorts, and one in kilt and bathing costume top who could have gone straight into the arena at Lonach.”

The temperature at Westminster that night never fell below 23.3C (73.9 F), a record for July that still stands.

The column goes on to describe the situation in the House of Commons where the heat had reached “almost Turkish bath intensity”.

“Some members were in natty tussore silk suitings, but this helped little, and it was many of their number who appealed to the Speaker to have more windows opened. The Speaker, panting like the rest of us, said they were all open. If they wanted more cool breezes from the Thames, members would have to smash the windows.”

This hot spell and others features in my Premier League of Heatwaves.

29071948

synop.PNG

850.PNG

June 2019: record heat spike

June 2019 saw no high temperature records broken but a jump in anomaly, produced on the 29th by the 3rd hottest June day back to 1959, is higher than any I can find back to that year..

The only phenomena similar that I can find, albeit in the other direction, is the Beast from the East in March 2018 that sent temperatures plummeting.

The month finished a little above average though the final figure, like May and April, masked cool warm spells.

The mean temperature finished 16.9C that’s 0.8C above average, the coolest for 3 years.

Rainfall was 63mm, 123% of average, the wettest for 2 years. Sunshine was 158 hours, 88.7% of average, and dullest for 3 years.

A timelapse of the longest day can be found here.

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

june 2019
‘Feels like’ maxima.
12.1
June 1981-2019 maximum anomalies
june anoms

 

The 12 month rolling rainfall total, thanks to a wetter than average month, has moved above 500mm again.

Summary for June 2019

Temperature (°C):
Mean (1 minute)  16.8
Mean (min+max)   16.9
Mean Minimum     12.1
Mean Maximum     21.7
Minimum          7.1 day 08
Maximum          33.6 day 29
Highest Minimum  18.0 day 24
Lowest Maximum   14.4 day 10
Air frosts       0
Rainfall (mm):
Total for month  63.3
Wettest day      18.7 day 10
High rain rate   20.1 day 09
Rain days        13
Dry days         17
Wind (mph):
Highest Gust     24.4 day 08
Average Speed    2.7
Wind Run         1932.6 miles
Gale days        0
Pressure (mb):
Maximum          1031.5 day 27
Minimum          998.4 day 07
Days with snow falling         0
Days with snow lying at 0900   0
Total hours of sunshine        0.0

 

 

 

 

 

 

 

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