Tag Archives: East London

Pressure peaks and troughs

Air pressure is probably the least celebrated meteorological statistic, most probably because unless you’re staring at a barometer all day you can’t ‘see’ it.

High pressure brings mostly fine weather while low pressure usually brings wind and rain – though it is the gradient of the isobars that can measure the impact each system can bring.

Steep falls and rises in pressure bring the most memorable events, in my case the October 1987 storm.

During the next week there will be a notable fall in pressure – but how will it compare with the past recent years? Looking at my own stats, a relatively small but complete set of 9am barometer readings back to May 2013, it does look like it will be notable.

The table below shows the numbers to beat.

As with many of these events the most impactful weather was found in the north of Scotland. The first period coincides with Storm Caroline.
The Met Office blog says Caroline brought a max gust of 93mph at Fair Isle and transport disruption and closed schools across the Western Isles.

Of course what goes down also comes up and pressure rises can be even more notable. In February 2016 the pressure rose 50mb in just three days, a week or so after Storm Imogen.

According to the Met Office FAX charts the 9am pressure in London on March 11th will be around 988mb, which would represent a fall of 48.6mb from 9am on March 6th.

London winter forecast 2020/21

The best chance for lying snow this winter looks like being at the end of the second week of January.

A combination of local analogues and global atmospheric factors including the El Niño-Southern Oscillation suggest that the coming season will be colder than recent years. Though that’s not saying much considering just how mild winters of the past decade have been.

Meteorological autumn was the warmest for 5 years and slightly drier than last year’s wet autumn. Though it shares some similarities with 2015 the external influences are thankfully different to that season which produced the warmest December on record. Considering data back to 1797 I was able to make the following suggestions on how the next 90 days may unfold.

December is most likely to be around average temperature-wise with rainfall also about average. Possibly stormy at the end of the first week. Any snowfall events are likely to be marginal – bad news for anywhere below 70m above sea level. In terms of Christmas a white one in London looks unlikely. There may be interest in the week running up to the big day but I wouldn’t be surprised to see that inexplicable warm up that often happens just as the 25th arrives.
Mean: 5.8°C (5.6°C 1981-2010 average)
Rainfall: 57.1mm (53.2mm 1981-2010 average)

January is the month most likely to see any lying snowfall, particularly during the first half of the month, with the mean temperature about 1C colder than average. Rainfall is likely to be above average.
Mean: 4.1°C (5.2°C 1981-2010 average)
Rainfall: 63.8mm (53.2mm 1981-2010 average)

February looks wet and mild overall.
Mean: 6°C (5.3°C 1981-2010 average)
Rainfall: 55.6mm (39.2mm 1981-2010 average)

Overall the mean for winter: 5.3°C, a little below average.
And rainfall about 120 per cent higher than average.

Looking in closer detail reveals that the coldest period is most likely to be between 13th and 19th January, with anomalies sufficiently low enough for lasting lying snow.

The extremes that no-one can forecast

As well as the extreme December 2015 the analogues also revealed the severe season of 1822-23 which saw ice on the Thames by late December. February 8th saw a great snowstorm in northern England where people had to tunnel through the snow.

Another was 1950-51 which was very snowy at high levels. There were 102 days of lying snow at Dalwhinnie (1000ft), exceeding the 83 days set in 1946-47. December 15th saw 15in of snow in Shanklin, Isle of Wight in 3.5 hours.

London’s colder than average months

Last November was on the cold side prompting me to investigate whether we were about to record a third month in a row below average. December turned out to be mild and wet, the lack of snow especially stark in Scotland.

The findings of that study showed that any sustained period of colder than average months was more likely to happen during months of March, April and May, nothing unusual there, especially considering H.H Lamb’s weather types.

I decided to scrutinise further all the colder than average months in this area, considering the 1981-2010 average, back to 1981. This gave the below results.

neg anoms

The dataset covers 399 months, of which 200 were colder than average.

The overall picture shows that negative anomalies are becoming more and more rare, though with notable exceptions being March 2013, December 2010 and January 2010.

The only month that has showed any sort of consistent general decrease in negative anomaly is November.

*For good snowfall at this station needs a negative anomaly of 2C during the months of November, December, January and February.

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

London winter forecast 2019/20

For this year’s winter forecast, because of time constraints, I am sticking purely to what the local analogues reveal.

Meteorological autumn was the wettest for 18 years and the coolest for 6 years, revealing some interesting similarities with past climate. Considering data back to 1797 I was able to make the following suggestions on how the next 90 days may unfold.

December is most likely to be on the cold side with rainfall slightly below average.

January is most likely to finish average temperature-wise and wetter than December.

London’s February extremes temperature also look average overall and the precipitation signal also creeps up in comparison to the first two winter months.

Best chance for snow? Impossible to pin down but the coldest weather is likely to be at the beginning of February, the third week of January and just after Christmas.

The warmest period looks to be around January 10th while there’s also a signal for that often phenomena of milder temperatures just before Christmas day.

Most of the probabilities in the above statements are relatively low and are explained in the table below.

Mean temperature 2019/20

December January February
1981-2010 average 5.6 1981-2010 average 5.3 1981-2010 average 5.3
Forecast median 4.4 Forecast median 4.7 Forecast median 5
Rather cold 40% Normal 40% Normal 44%
Normal 28% Rather cold 32% Rather cold 32%
Mild 20% Very cold 12% Mild 16%
Cold 4% Mild 12% Cold 4%
Very cold 8% Cold 4% Very cold 4%

 

Rainfall 2019/20

December January February
1981-2010 average 53.2mm 1981-2010 average 55mm 1981-2010 average 40.1mm
Forecast median 48.3mm Forecast median 55mm Forecast median 40mm
Wet 32% Wet 32% Wet 36%
Normal 20% Normal 28% Normal 36%
Dry 48% Dry 36% Dry 28%

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