Category Archives: UK rainfall

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

 

 

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The curse of June 13th

1 Jun 21 Jun 16 Jun 77

June can be a strange month weatherwise. Scorching temperatures as well as washout, cold weather, perhaps epitomised by the Queen’s Diamond Jubilee pageant on the river Thames in 2012, can feature prominently.

The month can also throw up some striking anomalies, none more so than the fact that the 13th is the only day in the month where the temperature has ever reached or exceeded 30C anywhere in the British Isles.

According to TORRO the highest daily maximum recorded in the UK is 28.3C at Earls Colne, Essex, in 1948; at Brixton, south London, in 1896 and Aboyne in 1994. Yet either side of this date has records comfortably above 31C, as the table below shows.

torro.PNG

The closest we’ve got locally to 30C in the last 60 years was in 1989 when 27C was recorded.

So why is the 13th ‘cursed’ with traditionally being the coolest day of the month? The best explaination perhaps is the fact that the date occurs more or less during the middle of the North-west European monsoon.

According to Philip Eden’s list of singularities the June monsoon can strike any time between the 1st and 21st but normally peaks on the 16th with a 77 per cent frequency.

As well as cool temperatures the phenomenon can also bring copious amounts of rain, as happened in 1903 when large parts of Redbridge were inundated following a 59-hour deluge that started on… the 13th.

Will we see a repeat this Thursday? Unlikely, though the general pattern is not that different to what led to events over a hundred years ago.

13th

 

 

Front loaded rainfall months

Since February most of this region’s rainfall has been falling during the first half of the month.

feb

February: 86%

march

March: 134%

april

April 28%

may

May (to 26th) 54%

With only one of these months wetter than average the long-term, rolling trend continues to head downwards.

rolling

Considering past rainfall patterns it can only be a matter of time before the graph heads upwards again. Looking further back at rainfall data to 1961 reveals the extremes were higher and that the jump from dry to wet can be sudden.

The wettest 12-month rolling period ended mid way through May 1975 with a total of 873mm. However, just 16 months later, at the end of the hot summer of 1976, the rolling 12-month average was just 302mm, that’s less than half of our average annual rainfall!

average rain

 

April 2019: average and dry

April finished average though the final figure masked cool and warm spells.

The mean temperature finished 9.7C that’s 0.1C below average and 2C cooler than last April.

Only 11.9mm of precipitation were recorded,  28 per cent of the 1981-2010 average and almost as dry as April 2017.

Some 170 hours of sunshine were recorded, that’s 106 per cent of average.

Four air frosts were recorded.

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

april2019max
‘Feels like’ maxima.
april 2019
April 1981-2019 maximum anomalies
april 1981-2019

Where’s east London’s rain coming from?

April 2019 was yet another dry month. Just under 12mm was recorded, that’s 28 per cent of average.

There has been rain around but the prevailing wind has not been conducive for great amounts to fall here. Last weekend, over a period of 5 days, just 0.9mm fall. Yet Capel Curig in Snowdonia, 200 miles northwest as the crow flies, recorded 130mm thanks to a NW’ly regime.

A look at rainfall in Wanstead back to July 2013 shows that of the 3,550mm recorded just 17 per cent has fallen when the wind was NW’ly.

Because of the topography of the area most of our rain falls when the wind is blowing between SE’ly and SW’ly, a total of 43 per cent.

A westerly is usually reliable for rainfall, however because this area is in the lee of high ground areas such as Hampstead westerlies have delivered just under 8 per cent of that 6-year total.

rain rose

March 2019: mild and wet

March was mild, particularly compared with last year. And wet though, like February, the rain fell at the start of the month, leaving a dry end.

The mean temperature finished 9.4C that’s 1.7C above average and over 3C warmer than last March.

Some 54.5mm of precipitation was recorded,  134 per cent of the 1981-2010 average.

Some  109 hours of sunshine were recorded, that’s  precisely average.

Just one air frost was recorded.

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

march 2019
‘Feels like’ maxima.
march 2019 feels like
key

Winter 2018/19: average with extremes

The winter of 2018/19 will probably be remembered most for the remarkable warmth in the last week of February. And for its lack of snowfall.

The mean temperature finished 6.1C, that’s 0.7C above average, the mildest for 3 years.

Rainfall was below average: 127mm fell, that’s 87 per cent of average and the driest for two years.

Sunshine was well above average: 211.6 hrs is 126 per cent over average, the sunniest for seven years.

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 first fell on 5 days between January 22 and February 1st: five days of snow falling and two days of snow lying over the three months is below average.

There were 29 air frosts during the three months, seven above the 1981-2010 average.

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

TMax winter

Summary for period 01/12/2018 to 28/02/2019

Temperature (°C):
Mean (min+max)   6.1
Mean Minimum     2.6
Mean Maximum     9.7
Minimum          -6.5 on 30/01/2019
Maximum          18.7 on 26/02/2019
Highest Minimum  11.5 on 06/12/2018
Lowest Maximum   1.3 on 23/01/2019
Air frosts       29
Rainfall (mm):
Total for period 127.0
Wettest day      11.4 on 20/12/2018
High rain rate   28.1 day 26/01/2019
Rain days        31
Dry days         59
Wind (mph):
Highest Gust     31.1 on 09/02/2019
Average Speed    2.8
Wind Run         6152.3 miles
Gale days        0
Pressure (mb):
Maximum          1043.8 on 02/01/2019
Minimum          980.4 on 01/12/2018
Days with snow falling         5
Days with snow lying at 0900   2
Total hours of sunshine        0.0

February 2019: very mild and sunny

February was most notable for how mild daytime temperatures were in comparison with night-time.

The 27th and 26th saw diurnal ranges of 19.4C and 19.3C respectively, the highest range recorded in any February since 1959, helped by huge temperature anomalies brought by the synoptic conditions. Although the UK maximun temperature record for February was broken with Kew Gardens reaching 21.2C the February TMax record in Wanstead, 19.7C set in 1998 remained intact.

The mean temperature finished 7C, 1.7C above average, the mildest February for 5 years.

Some 33.7mm of precipitation was recorded, 86 per cent of the 1981-2010 average, about the same as last year.

Some 124.6 hours of sunshine were recorded, that’s 170 per cent of average, the sunniest February for 11 years.

Ten air frosts were recorded.

There was one day where snow fell and one day of snow lying, 1cm on 1st.

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

feb max 2019
Summary for February 2019

Temperature (°C):
Mean (1 minute)  7.0
Mean (min+max)   7.2
Mean Minimum     2.5
Mean Maximum     11.8
Minimum          -3.9 day 02
Maximum          18.7 day 26
Highest Minimum  7.6 day 28
Lowest Maximum   2.2 day 01
Air frosts       10
Rainfall (mm):
Total for month  33.7
Wettest day      6.7 day 03
High rain rate   8.1 day 03
Rain days        10
Dry days         18
Wind (mph):
Highest Gust     31.1 day 09
Average Speed    2.7
Wind Run         1793.2 miles
Gale days        0
Pressure (mb):
Maximum          1038.4 day 25
Minimum          986.4 day 01
Days with snow falling         1
Days with snow lying at 0900   1

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?

A winter drought

Rain today (January 16th) is the first meaningful fall since before Christmas, putting an end to the 23-day long dry spell.

This meteorological drought, rare given that it spanned Christmas and New Year Storm singularities, these having 84 and 86 per cent probabilities respectively, was the 3rd equal longest winter drought.

The only other similar droughts in a list that dates back to 1887 were 19/12/2008 – 03/01/2009 and 17/12/1972 – 02/01/1973.

winter droughts

The last precipitation I recorded was from a weak occlusion that followed a cold front on the evening of December 23rd.

This synoptic set-up was followed by a build in air pressure that peaked on the morning of January 3rd; 1043.8mb was the highest reading in this area for at least 10 years and is the highest pressure I have measured.

A fuller version of London droughts in all seasons can be found here.