Tag Archives: East London weather statistics

London Winter Forecast 2021/22

This winter is most likely to be on the colder side of average with near normal rainfall.

While the modelled prognosis for the first half of December looks unsettled with an Atlantic influence evolving from the current chilly NW’ly to a mild SW’ly, local analogues of the climate of London suggest the season could be a bit of a rollercoaster with spells of wet, windy and mild weather alternating with dry, calm and cold.

A large factor to consider this winter is the presence of a slight La Nina that is forecast to evolve cooler.  

Given the uncertainties involved with the influence of ENSO I’ve decided to stick with analogues found in local data that stretches back to 1797.

Overall then the probabilities for the next 90 days are.

MeanProbabilityRainfallProbability
Mild (>5.9C)14%Wet (>178mm)19%
Average (5.1C – 5.9C)38%Average (107-177mm)62%
Cold (<5.1C)48%Dry (>107mm)19%

The above table doesn’t reveal a great deal in that extremes can be hidden in a month or season that finishes broadly average. So I decided to look closer at the winters that were revealed in the analogues.

December

The first month, as already mentioned, looks like it will be on the mild side with possibly a notable storm off the Atlantic before things calm down over Christmas – the period between Boxing Day and New Year’s Eve possibly presenting the best chance of any lying snow in this region.

The below graphs are a smoothed representation of the years revealed in the analogues most similar to this autumn.

What is probably most interesting is that the analogues that shared a similar ENSO / La Nina index to this autumn tended to ‘turbo charge’ any yo-yoing in the weather type, be that super-mild or abnormal cold.

December probabilties for maxima:
Mild: 48%
Average: 19%
Cold: 33%

And precipitation.
Wet: 33%
Average: 29%
Dry: 38%

So, the month overall will be mild and slightly dry

January

The first month of 2022 probably represents this region’s best chance of lying snow this winter. A mild start perhaps with a falling off of temperatures in the final third of the month and a cold spell of a week or so. As with December the influence of La Nina could tend to boost the swings in the pattern.

January probabilties for maxima:
Mild: 33%
Average: 10%
Cold: 57%

And precipitation.
Wet: 19%
Average: 43%
Dry: 38%

Greatest chances for January, then, are cold with average precipitation.

February

The second month may see a slight return of the cold spell in January before temperatures recover for a mild and wet spell in the second half.

February probabilities for maxima.
Mild: 33%
Average: 15%
Cold: 52%

And precipitation.
Wet: 38%
Average: 38%
Dry: 24%

The stats suggest on the cold side overall with average to above average rainfall. Perhaps the depth of the cold skewing any very mild second half of the month?


The extremes that no-one can forecast

As well as the very mild winter of 1989/90 the analogues also revealed the very cold winter of 1978/79. There were others but their occurence makes the probability of a repeat at either extreme at less than 10 per cent.

Four June washouts in london

Compiling a list of sunless, rainy days revealed some interesting spells of wet weather – the most miserable runs of June days in the capital since 1959.

First up was a three-day spell starting on June 25, 1974. Some 34.3mm of rain was recorded.

Next was a three-day spell starting on June 23, 1991. Some 26.3mm of rain was recorded.

Another three-day spell started on June 25, 1997. Some 36.2mm of rain was recorded.

Finally, and most recently, a two-day spell this month that began on June 17th. Some 28mm of rain was recorded.

The above spells all happened around the date of the ‘June monsoon’ singularity which has a probability of 77 per cent. Though the fact that these occurred 47 years, 30 years and 24 years ago shows that these extreme cases happen a lot less than three years in every four the singularity would suggest.

Comparing the current Northern Hemisphere pattern with 1974 suggests that while there’s just as much heat around at 850mb as there was 47 years ago, including an extreme heatwave over some Nordic countries, the air above Greenland appears colder.

Sunless days and washouts

The weather of late has been in stark contrast to the mostly dry, sunny (if a bit chilly) spring many enjoyed. Indeed the first half of June saw more of the same and, locally, was the warmest start to the first meteorological summer month since at least 1959.

My memory of summers years ago was that it was often hot and sunny but I also remember countless days of staring out the window for hours waiting for relentless rain to let up.

Looking back at sunshine stats to 1959 there has been over 4,400 days where no sun was recorded, roughly a one in five chance of a totally cloudy day.

Considering the months where the absence of sun is most noticed, May to October inclusive, the probability decreases to just under one in ten.

To decant these to ‘washout days’ I’ve only included those sunless days that were also ‘wet days’ where 1mm or more of rain was recorded. The probability further decreases to just under one in twenty.

All very interesting but were there more washout days decades ago or is the memory playing tricks?

Looking overall shows an increase since 2013. Out of all the months the most notable change has been August.

Spring in Wanstead Park

Spring in this neck of the woods was really mixed.

A chilly start to March became fairly benign before ending with the warmest March day locally since at least 1959.

April then turned much colder and drier; just 2.4mm of rain fell during the month – the driest April since 2007 and fourth driest in a local rainfall series back to 1797! Sunshine was abundant with over 200 hours. But clear skies at that time of year, with a polar continental airmass, often means air frost. And the ten recorded overnight was far higher than normal.

May saw things warm up slightly but the month still finished a degree colder than average. Some 80mm of rain fell which is over one and a half times what we’d normally expect. The wettest May since 2007 – the month playing catch up on the total absence of April showers that bring the spring flowers! It was a dull month with only 126 hours of sunshine, 69 per cent of average – the dullest since 1990 was third dullest back to 1881.


In terms of flora and fauna the colder weather played havoc with the trees, bud burst coming much later than recent years. As I write this on June 6th some of the later budders like false acacia have only just come into full leaf. The birds, as they normally do, just seem to get on with it raising their young. I’m not sure what the food supply has been like but judging by the amount of healthy juvenile fledglings I’ve seen I would guess that it has been a good season so far?


Here’s the stats.
March 8C (+0.3) 30.9mm (76%) 90.9 hours (84%)24.1C on 30th (a record that had stood since 1965)
April 7.2C (-2.6) 2.4mm (5.5%) 202.6 hours (127%)
10 air frosts in April, much higher than normal
May 12.1 (-1) 80mm (156%) 125.6hours (69%)
Spring 2021: Mean Thermometer: 9.1C (1.1C below average, coldest since 2013, 111th coldest) Rain Cloud with rain: 113mm (84% of average, wettest since 2018, 150th wettest ) Sun Sun with rays: 425.4 hrs (94% of average, dullest for three years. 51st dullest) The average masked extremes.

The relentless wind

Damage from Storm Ciara was a lot less notable than further north though the relentless wind saw three records broken locally. Though the gusts were nothing like the St Jude storm in October 2013 the sustained wind blew at its greatest 1, 2 and 3-day rate since this particular automatic station was reset in November 2012.

wind run

Over the 3 days the wind direction was locked in a south-westerly, from 199 to 203 degrees.

9th10th11th

2019 Wanstead annual weather review

This year finished as the 17th warmest on record – some 0.4C warmer than the 1981-2010 average. Although mild it was the coolest for six years.

After a dry start a wet autumn saw annual rainfall finish above average, the wettest for five years, 105 97 per cent of average.

Sunshine was down on 2018 though the total was just above average.

2019

2019 temp

2019 rain

2019 sun

For a review of each month, click JanuaryFebruaryMarchAprilMayJune, JulyAugustSeptemberOctoberNovemberDecember

You can read the national review of weather events at the Met Office blog here.

 

Summary for 2019

Temperature (°C):
Mean (1 minute)  11.7
Mean (min+max)   11.7
Mean Minimum     7.3
Mean Maximum     16.1
Minimum          -6.5 day 30/01
Maximum          36.8 day 25/07
Highest Minimum  19.6 day 23/07
Lowest Maximum   1.3 day 23/01
Air frosts       43
Rainfall (mm):
Total for year  667.4
Wettest day      20.6 day 19/07
High rain rate   65.8 day 09/08
Rain days        158
Dry days         207
Wind (mph):
Highest Gust     36.5 day 10/03
Average Speed    2.5
Wind Run         22211.5 miles
Gale days        0
Pressure (mb):
Maximum          1053.4 day 09/08
Minimum          969.8 day 12/12
Days with snow falling         5
Days with snow lying at 0900   2
Total hours of sunshine        1451

December 2019: wettest for 17 years

The December monthly mean finished 6.3C, that’s 0.7C above average, making it the ninth month of 2019 where the monthly mean temperature finished above average.

The wet theme of October and November carried on into December; the 111.1mm collected was 209 per cent of the 1981-2010 average, the wettest since 2002.

Some 51hrs of sunshine were recorded, 126 per cent of average, the sunniest for three years.

There were seven air frosts.

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

december t max

November 2019: coldest for nine years

The November monthly mean finished 6.4C, that’s 1.6C below average, the coldest November since 2010. It was the third month of 2019 where the monthly mean temperature finished below average.

The wet theme of October carried on into November; the 68.5mm collected was 116 per cent of the 1981-2010 average, slightly drier than last years.

Some 59.7hrs of sunshine were recorded, 102 per cent of average, the dullest for four years.

There were six air frosts.

You can find my thoughts on how winter is going to pan out here.

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

nov t.PNG

Summary for November 2019 – to follow

Months of perpetual cold

It’s been a while since this region has seen a sustained colder than average period. Though the past few weeks have seen colder than normal weather we have to go back to the beginning of 2015 where at least three consecutive months were colder than the 1981-2010 average.

The spell, which coincided with winter, was unremarkable with just one day of lying snow. The season finished 55th out of 73 of the most recent winters,  the anomaly for the 90-day period was -0.3C. For deep, lasting snowfall events a monthly mean temperature must be at least 2C colder than average.

For anything ‘snow-worthy’ you have to go back seven years to a 10-month long colder than average spell that began in September 2012 and coincided with probably the last winter I can remember that had more than one cold spell with snow that lasted longer than a few days. The average mean for this spell was -1.3C.

The most potent cold period occurred during the winter of 1984/85, a winter where snow lay nearly a foot deep by the end of January and where seven ice days were recorded – these days we’re lucky to record just one ice day per winter! Only just behind was the 3-month period January to March 1987.

As with previous blogs I have devised a way of ranking these cold periods, by dividing the mean with the length in months. The first nine months of 1986 achieved the highest ranking, a period that included the 5th coldest February in this area since 1797.

rank

And in chronological order…

chron

cold month index

It is looking like the mean this November will finish below average, making it the second month in a row, something that hasn’t happened since March last year. Will December make it three in a row and a new addition to the list?

 

October 2019: wettest since 2004

The wet theme of the final week of September carried on into October; the 100.3mm collected was 150 per cent of the 1981-2010 average, the wettest 10th month for 15 years.

The monthly mean finished 11C, that’s 0.8C below average, the coldest October since 2012. It is only the second month of 2019 where the monthly mean temperature finishes below average.

Only 72hrs of sunshine were recorded, 68 per cent of average, the dullest October since 2002.

The area’s first frost arrived 10 days before the median date back to 1959. And 3 days earlier than last year. A shower with >5mm hail was observed on the 9th.

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

oct max

Summary for October 2019

Temperature (°C):
Mean (1 minute)  11.5
Mean (min+max)   11.3
Mean Minimum     7.6
Mean Maximum     15.0
Minimum          -0.8 day 27
Maximum          20.4 day 14
Highest Minimum  11.9 day 05
Lowest Maximum   10.3 day 28
Air frosts       1
Rainfall (mm):
Total for month  100.3
Wettest day      16.6 day 05
High rain rate   20.1 day 01
Rain days        20
Dry days         11
Wind (mph):
Highest Gust     21.3 day 25
Average Speed    2.0
Wind Run         1492.7 miles
Gale days        0
Pressure (mb):
Maximum          1026.6 day 29
Minimum          996.6 day 01
Days with snow falling         0
Days with snow lying at 0900   0
Total hours of sunshine        72