All posts by wansteadmeteo

A blog that tries to make sense of how the UK's national climate translates into local weather for Wanstead and the surrounding regions of east London and west Essex. Check out my twitter feed @wanstead_meteo for local weather forecasts, stats, records and phenomena for the east London areas of Wanstead, Aldersbrook, Leytonstone and Stratford. And anything else weather

Forecast, month ahead forecast, monthly summary, Weather

May 2015: average temps and dry

June 1, 2015 wansteadmeteo 3 Comments

After a sunny and dry April last month was disappointing for anyone looking for prolonged heat and sunshine. Indeed the month saw nearly two dozen less hours of sunshine than April.

During a very thundery day nationwide on 19th it was bright and sunny looking west on Southwark Bridge at 3.40pm... — During a very thundery day nationwide on 19th it was bright and sunny looking west on Southwark Bridge at 3.40pm…

Maximum temperatures were low for May – the highest being just 23.3C on 11th, 2C colder than the highest temperature in April.

Mean temperature for the month was 13.4C, 0.3C above the 1981-2010 mean. Rainfall of 38.9mm was 76% of average – six of the last seven Mays have been notably dry.

There were 178.5 hours of sunshine recorded in this area which is 98% of what we can expect to see during an average May. The wettest day occurred on the 4th with 8.2mm.

So what has June got in store weatherwise? The models this morning (June 1st) suggest a very unsettled start to the month before the Azores high builds a ridge to quieten things down for a couple of days. Beyond that is uncertain – the ensembles point to a very mixed picture with no clear trend shown to where we might be in a fortnight’s time.

Looking east was a different story which revealed a distant thunderstorm

Looking at the month as a whole my long range method suggests June will be average in terms of temperature: 54% probability. The next highest chance is for rather cool at 15% probability. If you add the probabilities together the chance of average to below average temperature is 85% – which would seem to rule out a ‘very warm’ month…

Rainfall is looking average to slightly above average, though at only 62% probability. It looks like another broadly average month in terms of sunshine.

So with a slightly changeable start to the month we can look forward to another average month without prolonged heatwaves?

My May outlook was good in that it saw the high chance (80%) of average temperatures. I was, however, out with the low rainfall – the signal was for something greater than average. Sunshine, as already mentioned, was also out – my forecast was for something 1.2 above average.

May 19th was a very thundery day across eastern England. This picture was taken looking east from Southwark

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

Here follows the full weather diary for May…

1st: Sunny start but cloud quickly filled in. Though cloudy it remained bright. Cold wind.
2nd: Cloudy start but becoming brighter. Turned to hazy sun at 3.30pm but then turned cloudier. Rain by early hours, 5am and then again at 8.30am.
3rd: Cloudy after early rain then growing warm and muggy with sunshine at 2pm. It stayed bright and muggy into the evening.
4th: Sunny start then haze and cumulus soon thickened before clearing to sunny spells early lunchtime. Cloud built up again at 2pm. Rain spread in early evening with heavy bursts from 11pm to 1.30am – heaviest at midnight.
5th Cloudy start but becoming brighter albeit very windy through the morning and past lunchtime. Occasional showers with very heavy shower at 6am.
6th: Cloudy start with brighter interludes but turning very blustery with occasional light showers. These turned heavier through the day with a notable one at 2pm. Thunder heard at 5pm with more showers.
7th: Sunny start but with lots of cloud bubbling up

Wanstead was hit head-on by a thunderstorm at 2pm on 19th, clearly shown on this radar picture. Because the storms were fast moving rainfall accumulation was not remarkable

8th: Bright start after early light shower. Spots of rain during bright afternoon – these turned heavier at 3.30pm. Cloudy and mild overnight.
9th: Bright, slightly breezy start. Spells of very warm sunshine though also odd spots of rain during showers.
10th: Bright start with sunny spells through the day
11th: Bright start with altocumulus. Cloud broke to sunny spells though sky was very hazy at times. Feeling humid. Warm overnight but short, sharp shower moved in 10 minutes before obs time.
12th: Light rain to start from a frontal feature. This clearing to sunny spells and pleasant afternoon
13th: Sunny with few cirrus to start. More cloud bubbling up later. Clear at first overnight before cloud and light rain moved in before 9am.
14th: Cloudy but spits and spots of rain spread in, before more steady light rain at 10.30. This eased at noon before becoming heavier again at 3.30pm and rained into evening, easing up at midnight.
15th: Sunny start though cloud tended to fill in. Some rain around midnight
16th: Cloudy start though got progressively sunnier as cold front cleared, humidity fell and cloud melted away. Very pleasant. Cool overnight.
17th: Sunny, clear start with a few cirrus. Cloudier at times but still sunny spells. VERY breezy with f4/5 headwinds on ride to station. Rapidly changing skies with wind shear.
18th: Some light rain to start, this intermittent through the morning.
19th: Bright and breezy start. T-storm developed at 2.30pm but moved through quickly. Was two more, at 5pm and 7pm – notable rises in pressure as troughs moved through.
20th: Bright start. Light shower bubbled up late afternoon.
21st: Sunny start, cloud gradually filled in though.
22nd: Bright start with sunny spells. Warm.
23rd: Cloudy with a very thick layer of strato-cumulus making it dull. Two hours of light rain and drizzle followed but cleared to leave it bright with a couple of sunny intervals in the evening. It felt humid at first but turned much fresher once the drizzle cleared.
24th: Sunny start though cloud filling in to make it bright. Frontal light rain between 3 and 5pm.
25th: Cloudy most of the day, a few bright intervals though spits and spots of drizzle early evening.
26th: Sunny start with fluffy cumulus. Pleasant.
27th: Dry, warm and sunny all day. Heavy rain in York from 3pm to 8pm. Felt chilly in the wind.
28th: Dry, lots of cloud around
29th: Dry start though rain moved in between 11am and 1pm. Then sunny spells and breezy.
30th: Sunny though soon clouded over before clearing again to sunny spells. Mackerel sky observed at 8.30pm. Rain between 2.15am and 6.30am.
31st: Light rain to start with outbreaks throughout the morning. Some brightness mid to late afternoon.

Events, Forecast

UK media in a fog over El Niño predictions

May 13, 2015 wansteadmeteo Leave a comment

When it comes to explaining weather phenomena the British media has often been found wanting over recent years. But when the Australian Bureau of Meteorology yesterday confirmed the emergence of a fresh El Niño newspapers and TV stations inevitably reached the conclusion that the phenomena will trigger a severe winter in the UK.

Sky News told us that it “could also result in a harsh winter for the UK; during the last El Nino in 2009/10, Britain suffered heavy snowfall”, before showing us newsreels of what looked like conditions in December 2010 – the winter after.

Not to be outdone the Daily Telegraph moved the effects forward to this summer, telling us the effect *could* herald a “damp summer with temperatures well below average”.

I decided to have a look at the facts to see what the effect of an El Nino episode was by comparing the US weather agency NOAA’s data on ENSO episodes going back to 1950 with my own data. For speed I used my top ten snowy winters and compared against the NOAA data. The results showed that eight cold winters followed an ENSO pattern that was negative. The winter of 2009-10 seems to be the exception to the rule. Indeed, a significant El Niño episode in 1997/98, preceded the third warmest winter in my series going back to 1797!

El Niño / ENSO is just one variable when it comes to forecasting a season ahead. Other variables to consider are AO, QBO, MJO and this is before SSWs, sudden volcanic eruptions and sunspot activity throw spanners in the works.

It is exasperating that both the Sky and Telegraph stories were copiously shared on social media – prompting the inevitable comments along the lines of: “They’re talking rubbish, they can’t forecast what that weather will be tomorrow!”

But rather than badly informed journalists it is the Met Office and other noble agencies who will share the blame if the story is incorrect.

There is no doubt that El Niño will disrupt the weather around the Pacific rim but, considering the data we have available, I don’t think it, alone, will be the reason Britain may experience a severe winter this year.

* XMetman has had a long look at the data and couldn’t find a link either

** NOAA’s monthly diagnostic discussion just released (14/5) says:

“There is an approximately 90% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 80% chance it will last through 2015.”

Read full advisory here

Forecast, month ahead forecast, monthly summary

April 2015: very dry and sunny

May 1, 2015 wansteadmeteo 2 Comments

April showers bring spring flowers – or so the saying goes. The month was actually sunny and very dry with less than 50% of what falls in a normal month.

The cold nights and often chilly days helped to preserve spring blossom, with some stunning displays on streets around the borough.

Indeed just one day, the 30th, was what you could say was a classic April day – a sunny, clear morning saw convection build towering cumulus clouds with a light shower around lunchtime.

Mean temperature for the month was 10.6C, 0.8C above the 1981-2010 mean, over 1C cooler than April last year. Rainfall of 18.9mm was 45% of average – six of the last seven Aprils have been notably dry.

There were 201 hours of sunshine recorded in this area which is 126% of what we can expect to see during an average April. The wettest day occurred on the 25th with 4.7mm. Air frosts: 5 Ground frosts: 13

So what has May got in store weatherwise? The models this morning (May 1st) suggest next days remain unchanged with troughs moving NE across the UK over the weekend introducing warmer air with a mix of sunshine and showers following. A new LP looks like developing over western France on Monday becoming absorbed in the main low to the west of the UK bringing a more sustained westerly feed ahead of rising pressure from the south later toward the weekend, bringing fine and summery conditions. The risk of rain should decrease as the week goes on.

Beyond that the outlook, as ever, is uncertain.

My long range method suggests the month will be average in terms of temperature: 80% probability. The next highest chance is for rather mild at 20% probability. Rainfall is looking average to slightly below average, though at only 60% probability. It looks like another sunny month is in prospect – 80% probability of sunshine at 1.2 times the mean.

So with a slightly changable start to the month we can look forward to another sunny, pleasant spring month without heatwaves?

Long spells of cirrus gave a solar halo on the 17th.

My April outlook was good in that it ruled out any chance of a very mild or very cold month. The combined probability of 72% for an average to rather mild month was correct. I was, however, completely off with the rainfall, the signal for which was greater than average

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

Here follows the full weather diary for April…

1st: Bright start but very breezy through the morning and afternoon. Rain after 11pm and again at 3.30am.
2nd: Bright start though sunny spells increased through the day. Felt really pleasant out by noon. Some rain in the early hours before obs time.
3rd: Cloudy through the day with some rain late afternoon.
4th: Cloudy all day though with some drizzly rain. Some brightness was seen on way in to South Kensington in the Whitechapel area.
5th: Cloudy, cold start but with sunny spells developing through the day. Pleasant in the sun.
6th: Sunny start with cloud building from time to time. Cloud cleared overnight to give a ground frost.
7th: Sunny start with long clear periods through the day.
8th: Cloudy start gradually cleared to hazy sunshine. Cloudier again in afternoon.
9th: Cloudy start though soon brightening up for a sunny day in town.

Typical April days of sunshine and showers were in short supply. There were some stunning sunsets, including this one on the 30th

10th: Cloudy start though cloud quickly thinned to leave sunny day. However, cloud was hazy at times with bad pollution seen over London. Also a few drops of rain were observed rain around edge of Ornamental Waters. Humid.
11th: Drizzle turned to moderate rain that was over in 45 minutes and cleared to sunny intervals, then longer sunny periods through the day. Much cooler than yesterday.
12th: Sunny start led to a day of long sunny spells. Sky was initially a deep blue but hazy cumulus built up after 4pm.
13th: Cloudy start, some brightness in the afternoon.
14th: Sunny, gin clear start. Sunny all day with light breeze taking edge off temp.
15th: Sunny, clear start for RMetS meeting. Slight breeze kept edge off temp. Some light clouds late afternoon. Cooling off quickly in early hours.
16th: Sunny spells in the morning.
17th: Sunny though long spells of cirrus gave a solar halo. Chilly in the wind.
18th: Sunny spells to start though cloud decreased to leave gin clear afternoon. Dew point dropped to 1.5C making it feel very chilly.
19th: Bright start but cloud quickly filled in leaving it feeling cold in the wind. Some sunshine after 5pm making it a pleasant if a bit cold in the wind evening.
20th: Sunny and mostly clear all day. Much warmer.
21st: Sunny and mostly clear all day. More contrails though. Chilly overnight again.
22nd: Sunny start though cloud filled in earlier than yesterday. Nowhere near as warm.
23rd: Cloudy start though the cloud decreased and was gin clear by 12.15pm.
24th: Sunny start although hazy at times. Cloud gradually increased late afternoon and light rain arrived 1am.
25th: Cloudy start though plenty of breaks in the cloud developed allowing for a pleasant afternoon.
26th: Slight drizzle to start then cloudy and cold all day. Cold overnight in clearer spells.
27th: Sunny start. Clouds bubbled up though the day with showers reported elsewhere. It threatened rain in Wanstead but stayed dry.
28th: Sunny start with just a few clouds through the day. Feeling cold though.
29th: Light rain to start though this suddenly cleared at 10.15am before clouding over again.
30th: Sunny start with clouds bubbling up. A light shower in Snaresbrook.

historic trees London, History, Weather

Veteran trees that make Wanstead Park

April 11, 2015 wansteadmeteo 1 Comment

As the trees in Wanstead Park start bursting into life it is interesting to note that the oaks seem to be beating the ash trees into leaf.

One of the magnificent oaks that provide the backdrop to Music in WansteadPark was in leaf on Friday, April 11th.

After the dry vernal equinox period this could be another sign of a dry summer to come as the saying goes…

If the oak before the ash then we’ll only see a splash.

If the ash before the oak then we’re sure to get a soak.

The story behind the mature trees in Wanstead Park – several of which will turn 200 this year – is a fascinating one.

The park is virtually on my doorstep and it’s like watching a living painting as the trees change from season to season. Spring is my favourite time of year, as the character of the park transforms so quickly. Chalet Wood bursts into colour with a carpet of bluebells, and leaves once again clothe the trees.

Magnificent specimens of oak, horse chestnut, sycamore and holly stand alongside half-rotten victims of gales over the last 200-odd years. But despite storms and floods, the biggest nemesis to these trees was the former owner of the park, William Long-Wellesley. As well as demolishing Wanstead House in 1823 to help clear his debts, Long-Wellesley also sold thousands of mature trees, despite local opposition and a court injunction brought by Sir Edward Sugden, who was seeking to restrain Long-Wellesley’s depredations on his children’s inheritance.

A court report from the time states that Long-Wellesley had marked 2,000 trees for sale, which would have included hardwoods, such as oak, chestnut and elm and perhaps walnut and lime. To quantify that figure, it should be noted that the last full tree survey of the park, not including Bush Wood, in April 1990, listed just over 800 trees.

Richard Arnopp, committee member of the Friends of Wanstead Parklands, said: “There is general agreement that Long-Wellesley left the park more or less devastated, but the wooded areas subsequently regenerated within their former footprints, helped by later planting and management by the Corporation of London.”

It is not clear who bought the trees, though oak was especially valuable at the time for shipbuilding, which was still some decades away from the shift from timber to iron. Britain was at the end of the first Industrial Revolution and timber suitable for making masts, a crucial requirement for any sailing ship, and one that often had to be replaced after storms or wear, was difficult to find.

This graph shows the monthly mean temperature for the periods 1814-1825 (series 1, blue line) and 2004-2015 (series 2, orange line). Notice how much colder most winters were 1814-1825

It was also a cold period. Just over 10 years previous the Thames froze over for the last time and winters were frequently very cold and snowy. Wood was one of the principal methods of keeping warm – house fires would have been burning through the winter – anyone with a wood stove would know just how much wood you can get through, even in an average winter.

As well as selling timber, Long-Wellesley reportedly sold the topsoil of Wanstead Flats to nurseries as potting compost. Most of the mature trees in the park today would have been saplings in the 1820s, thus escaping the attention of Long-Wellesley. According to the Debois survey from 1990, the cedar tree near the Ornamental Water has this year reached its 200th birthday. Also 200 years old this year are the three magnificent oaks next to the Temple, one of which has increased in girth from 319cm to 372cm since 1990.

The trees were protected for future generations when the Epping Forest Act was passed in 1878. Since that time, the Corporation of London has managed their welfare and a new initiative will soon step up this care and reinstate even more of what was lost during Long-Wellesley’s tenure.

* There is much more detail at the site http://www.wansteadpark.org.uk/

** The author has studied forestry and arboriculture at Capel Manor College in Enfield

Weather, weather pattern, weatherlore

Spring signs for a dry summer?

April 3, 2015 wansteadmeteo 1 Comment

What kind of summer is in store this year? According to Richard Kirwan’s weatherlore we’re odds on for a dryer than average season.

Summer overlooking The Temple in Wanstead Park by Wanstead Meteo — Summer overlooking The Temple in Wanstead Park

Kirwan, a Dublin-based chemist with a keen interest in the weather, deduced from observations made from 1677 to 1789 that the weather around the spring equinox provided a very good pointer to what was in store in the months ahead.

The lore, noted in Luke Howard‘s Climate of London, suggests that the probability is five to one in favour of a dry summer.

The detail, however, hinges around key dates.

1/ When there has been no storm before or after the vernal equinox the ensuing summer is generally dry, at least five times in six.

2/ When a storm happens from an easterly point on the 19th, 20th, or 21st of March the succeeding summer is dry, four times in five.

3/ When a storm arises on the 25th, 26th, or 27th of March, and not before, in any point, the succeeding summer is generally dry, four times in five.

4/ If there should be a storm at SW, or WSW, on the 19th, 20th, or 22nd of March, the succeeding summer is generally wet, five times in six.

Howard goes on to say: “Dry summers (this philosopher states) are the consequence of uniform winds, from whatever quarter they may blow; as wet summers are of their variation, particular if in opposite directions.”

Again, “Southerly winds are most frequently accompanied with rain in most parts of Europe at least, and probably in most parts of our hemisphere; but northerly and easterly, with clear dry and serene weather.”

And it seems reasonable to suppose that the wind which is to prevail during the summer, may most frequently set in with the vernal equinox.”

I’ve had a look back through my own records and this theory falls down, when you consider the absolute detail, on notable summers including 1995. But then, just like weather forecasting at short range, it is all about ‘chance’ – five times in six is still only an 83 per cent certainty.

There is also the matter of how Kirwan and Howard defined a “storm”. What we would call a storm now would be very rare in the second half of March anywhere around London, possibly less rare in the Dublin area. I am also assuming that Kirwan remembered to take into account the switch from the Julian to the Gregorian calendar in 1752.

What is notable, however, is how far ahead of their time Kirwan, Howard and other scientists were in having the thought to notice these patterns – something that continues to fascinate amateur and professional meteorologists alike today.

month ahead forecast, monthly summary, Weather

March 2015: dry and sunny with av temps

April 1, 2015 wansteadmeteo 3 Comments

The saying March: in like a lion, out like a lamb and vice versa is frequently wrong. This March saw it windy at the beginning, end and middle of the month.

This graph shows the 'wind run' of every day in March. Notice how the peaks are at the beginning, middle and end of the month — This graph shows the ‘wind run’ of every day in March. Notice how the peaks are at the beginning, middle and end of the month

Mean temperature for the month was 7.6C, 0.1C below the 1981-2010 mean, over 1C cooler than March last year. Rainfall of 17.9mm was 44% of average – four of the last five Marches have been notably dry.

There were 131.5 hours of sunshine recorded in this area which is precisely 121% of what we can expect to see during an average March. The wettest day occurred on the 29th with 4.2mm. Hail fell on 1 day. Air frosts: 5 Ground frosts: 13

So what has april got in store weatherwise? The models this morning (April 1st) suggest a dominance of high pressure though there’s lots of uncertainty as to where this will drift once it has formed over the Easter weekend. If it moves north there is a risk of chilly easterly winds at times that will take the edge off temperatures.

Rainfall amounts will be small after the next couple of days though sunshine amounts will be reduced if we get the cold easterly feed off the continent. Beyond that the outlook, as ever, is uncertain.

My long range method suggests the month will be average in terms of temperature: 43% probability. The next highest chance is for rather mild at 29% probability. Rainfall is looking greater than average, though at 57% probability.

My March outlook was good in that it ruled out any chance of a very mild month. Though the signal was for a cold month overall I think the fact that Scandinavia and Russia had a relatively mild winter meant that the resulting overall temperature was far milder than it normally would have been, given the air flow.

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

Here follows the full weather diary for March…

1st: Sunny start with more cloud afternoon and a rain squall sweeping through at 5.30pm. Cold wind.
2nd: Sunny start though cold wind. Odd shower.
3rd: Sunny start but with cloudier periods and odd spot of rain up to 2pm. Skies turned really dark to the north but no reports of heavy rain. Cold overnight but no air frost due to the wind.
4th: Sunny spells with cloudier intervals.
5th: Sunny, frosty start. Cloud bubbling up with sun becoming scarcer.
6th: Sunny and clear with just a few cirrus.
7th: Sunny start, just a few cirrus though more breeze
8th: Sunny start though more clouds bubbling up than yesterday.
9th: Sunny start was quickly replaced by overcast conditions. Spots of rain on way into work – signs of something heavier when left work at midnight. Clear again by morning.
10th Sunny start with some cirrus type haze. Cloud bubbled up but sunnier than yesterday.
11th: Sunny start, cloud growing thicker through the day before a pink sunset. Some light rain before a clear night.
12th Sunny start and just a few clouds around. Cloud thicker in afternoon.
13th Hazy bright start though cloud thickened.
14th: Sunny start quickly turned cloudy and dull. More brightness in afternoon though cold wind. Early shower at 6.30am.
15th: Dull start into the morning. Some light rain late morning and during the afternoon. More rain after midnight and just beofre dawn.
16th: Cloudy start though with bright intervals in the afternoon. Area of light rain around 4am.
17th: Cloudy start with light rain spreading in. Brighter by 1pm though very misty on ride in to work. Misty again overnight.
18th: Cloudy, misty start though much more sunshine than yesterday on ride to Lea Valley. Cloudier overnight.
19th: Cloudy and dull all day, feeling cold – the cloud persisting into the evening.
20th; Cloudy start for the eclipse. The sky cleared about 12.30pm to leave bright sunshine and a pleasant, springlike afternoon. Early ground frost before sky clouded over.
21st: Cloudy but some spots of drizzle mid-morning. Dry and cloudy afternoon.
22nd: Sunny start though cloud increased through the day. Felt cold in the wind.
23rd: Bright start with lots of sunshine through the morning. Gradually filling in though feeling much milder than of late. Some light rain in the evening, heaviest between 3.30am and 5am.
24th: Cloudy start though with some bright spells. A short shower at 3ish.
25th: Sunny, cloudy start though with lots of high cloud filling in. Brief ground frost moved in just before midnight before rain moved in just before 4.30am.
26th: Drizzly light rain to start – felt cold. Not a nice day.
27th: Bright start with lots of watery sunshine through the day. Spits and spots of rain later as walked home from Wanstead.
28th: Cloudy start and mild with some brightness. Feeling mild. Some rain overnnight.
29th: Drizzly start with heavier bursts of rain, these fell through the day, drying up in the evening.
30th: Bright start with some sunny spells. Wind increased in strength through the day and was very strong overnight.
31st: Bright start after a stormy overnight that prompted a tug rescue that overturned in the Solent. Dartford Bridge was also closed. Showers surrounding Wanstead but only trace here – hail seen in City. Cold and windy overnight.

Weather

Eclipse 2015 in Wanstead

March 20, 2015 wansteadmeteo Leave a comment

While heavy low cloud obscured the partial eclipse in this area there were a couple of interesting factors that I observed.

At 9.45am, shortly after the maximum obscuration of the solar disc the air pressure suddenly dropped. This coincided with sudden relief to my blocked nasal passages, symptoms of which appeared last night. Eighteen minutes later the fall in air pressure became less steep and the nasal symptoms returned.

The pressure dropped from 1029.8mb at 9.15am to 1029mb at 10.15am. I'm not sure if it was an effect of the eclipse or just a change in the synoptic situation that would have happened anyway — The pressure dropped from 1029.8mb at 9.15am to 1029mb at 10.15am. I’m not sure if it was an effect of the eclipse or just a change in the synoptic situation that would have happened anyway

As the light began to fade it seemed to turn colder though, on looking at the actual figures, the effect of the partial eclipse through heavy cloud was a depression in temperature of 0.3C. I worked this out by comparing today with yesterday which had almost identical weather conditions. People remarked that it turned noticeably colder though perhaps this was more caused by standing out in temperatures of 4.9C for a long period.

Like the eclipse in 1999 I noticed that the birdsong quietened somewhat though there was not the same crescendo of noise that you normally get at dusk when birds roost.

Here is the temperature trace from the 19th. Even with the heavy cloud yesterday there was more warming from the sun, albeit by a very small 0.3C

This graph shows the temperature from 6am until 11am. Though the depression during the eclipse was just 0.1C comparison with the previous day, which saw near identical weather conditions, shows just how much solar heating was depressed

Seasonal summary, Winter forecast

Winter 2014/15 – second sunniest on record

March 1, 2015 wansteadmeteo 1 Comment

This winter was the second sunniest on record in this region. Sunshine hours totalled 238 hours during December, January and February – that’s 142% of average and second only to 2007/08.

It was the sunniest December on record in the series going back to 1979. Some 11 mornings were completely clear at the 9am observation time — Winter 2014/15 was the second sunniest on record with 238 hours of sunshine

The first lying snow for two years is also a notable observation of winter 2014/15. That it lasted just a few hours emphasises how little snow there was at sea-level for the second winter in succession.

The mean temperature of 5.2C was just 0.3C below the 1981-2010 average. Some 152mm of rain fell – that’s just 7mm over the winter average.

Winter began with the sunniest December on record in my series going back to 1877. Over 90 hours of sunshine was recorded in this area which is 224% of what we can expect to see during an average December.

January saw the first falling snow in nearly two years with the last three days of the month seeing the first flakes of winter – nothing much to write home about by average winter standards.

February produced the first lying snow in nearly two years. The 1cm depth at 9am on 3rd, however, is nothing much to write home about by average winter standards.

The wettest day during the three months was January 12th when 13.1mm fell.

Snow fell on 6 days. Air frosts: 27 Ground frosts: 48

Full stats for winter can be found here: http://1drv.ms/1rSfT7Y

At the end of November I published my annual winter forecast. I said the season would *probably* be colder with a better chance of snow than last winter. If I’m honest I thought we’d see more incidents of snowfall though, with my predicted mean temperature of 4.2C being exceeded by 1C, the air around the UK just wasn’t cold enough for snow at sea level. My predicted rainfall was more impressive – I forecast 156mm and was out by just 4mm!

Obviously when the season is average long-range forecasts like this have a much higher chance of being correct. One could argue that basic climatology has made my forecast look a reasonable one. But I stick to what the stats suggest and try to steer clear of the endless hyperbole published almost daily by certain tabloids.

month ahead forecast, monthly summary, Weather

February 2015: average

February 27, 2015 wansteadmeteo 2 Comments

feb3rd snow — A snowfall on the 3rd just about covered the ground for a few hours, though was barely enough to make a snowball

Though it only lasted a couple of hours this February saw the first lying snow in nearly two years. The 1cm depth at 9am on 3rd, however, is nothing much to write home about by average winter standards.

Mean temperature for the month was 4.9C, 0.4C below the 1981-2010 mean, 2.5C cooler than the mild and stormy February of last year. Rainfall of 43.6mm was 111% of average.

There were 73.6 hours of sunshine recorded in this area which is precisely 100% of what we can expect to see during an average February. The wettest day occurred on the 19th with 8.7mm. Snow fell on 3 days, hail on 2. Air frosts: 4 Ground frosts: 19

So what has March got in store weatherwise? The models this morning (March 1st) suggest a taste of spring – the recent cold and showery regime being replaced by quiet, anticyclonic weather. Output suggests variable cloud cover with a mild SW wind. Obviously sunny days will see quite respectable temperatures though any clear nights will see frost and mist developing.

View from top of Ditchling Beacon in Sussex during a half-term walk

Beyond that the outlook is uncertain. Using a similar method to my Christmas forecast, which was correct at 25 days ahead and my January and February outlooks, I’ve had a look back in the archives to see if there is any precedent in the pattern we’ve had this February.

There appears no chance of a very mild March. The strongest signal (67%) is for a cold March. The strongest signal for precipitation is for average to slightly below (83%). Sunshine, no overall signal, so my guess is average.

Though we are now out of the meteorological winter there is still a risk of snow. Any falls, however, would be thin and transitory because of the strength of the sun now.

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

Here follows the full weather diary for February…

1st Bright start with sunny spells thoughout the day

2nd Sunny start but soon clouded over. Cleared again in evening though with lunar halo. Showers moved in after midnight and into early hours to leave thin coating of snow by 8am.

3rd 1cm at 9am. A bright start though with lots of cloud around. Sunnier in afternoon, the snow had melted by 1pm. Variable clear spells through the night but too cloudy for frost.

4th Cloudy start but some brightness. The sunshine felt warm at times. Variiable cloud overnight. Woke up to see snow falling but too warm to settle – the air being 1.2C, dew point 0.5C

5th Some spots of sleet to start and during the day. Colder air digging in from 3pm. Feeling bitter.

6th Bright start, cloud decreasing through the day to give long sunny spells. Cold wind

7th Cloudy and cold start

8th A sunny start with long sunny spells all day

9th Mostly cloudy to start though bright and breaking to sunny spells and then unbroken sunshine.

10th Cloudy and cold all day

11th Dull and cloudy all day

12th Dull start and stayed dull all day. Cold. Warming up after 2am with some very light rain with warm front.

13th Bright spells through the morning with a brief clearance around 1pm. Rain soon arrived though and fell through the afternoon and into the evening. Rain again from midnight until 2am

14th Bright intervals to start though mostly cloudy through the day. Some very light rain showers through the day and into the night

15th Cloudy start though with bright intervals becoming more frequent. Clear by dusk allowing temp to fall quickly

16th Cloudy start with rain spreading in after 1pm, moderate at times

17th Unbroken sunshine until 1pm then a few clouds. Cold overnight on boat

18th Sunny most of the day with only a few high clouds

19th Sunny until mid morning then clouding over quickly. Rain pushed in late lunchtime and lingered all day and into evening. Stayed dry on walk until 2.30pm but very stong wind ahead of rain band

20th Cloudy start though bright through haze at times. Feeling cold. Cloudy into evening with area of rain at 7am

21st Sunny start after rain at 7am. Very cloudy at times with light hail <5mm – the sky suggested the hail was heavy elsewhere. Reports of snow in Oxford. Frosty overnight

22nd Sunny start but cloud quickly filled in before rain arrived at 3pm. Temp then rose to a high of 9.5C at 11pm before falling at midnight

23rd Sunny start but with cloud bubbled up and some light hail mixed in with showers. Feeling cold

24th Sunny start with some cloud bubbling up. Heavy hail shower at 3.30pm. Temp built through the night with rain 5.30am – 7.30am

25th Drizzly start broke to sunny spells. Much milder. Drizzle overnight after 3.30am

26th Cloudy start with rain late morning. Cold front blew through around 2pm. Clear and frosty overnight

27th Sunny, cold start. Cloud gradually increased through the day. Temperature lifted a little – spits and spots of rain felt on way home

Events, History, Weather

Luke Howard’s solar eclipse of 1820

February 24, 2015 wansteadmeteo 2 Comments

The partial solar eclipse taking place on March 20th left me wondering if there is any record of past events for this area.

Luke Howard‘s The Climate of London describes a similar such event that took place on September 7th, 1820. Howard describes how the thermometer fell from 68.5°F to 62.5°F. After making observations at his home in Tottenham at 10.30am Howard made his way to Stoke Newington to visit fellow scientist and Quaker, William Allen, to observe and record the eclipse.

From his account it appears that, though the weather was settled, there was a fair bit of cirrocumulus drifting across the sun during the eclipse.

As well as the fall in temperature Howard’s account describes the strange light: “The sunshine against the house was so dim as to be quite striking; and the view before us to south, which included the nearer parts of London, showed much the same as afterwards at six In the evening – dusky but not dark.”

Howard noted that the lowest temperature was observed about seven minutes after the greatest obscuration. He also mentions that his son noticed that spots of light falling through the shade of trees were in the shape of crescents, mirroring the lunar disc across the sun, rather than globular. He also states that Venus was very easily visible during the eclipse.

Though Howard’s account is by no means groundbreaking, it would be another hundred years before another eclipse proved Einstein’s theory of general relativity, it is fascinating how we are still just as fascinated by the sun as our forbears were.

I was in southern Turkey for the last solar eclipse which I believe was overcast in the London area. I had some data from my then AWS but I’ve misplaced it. That Oregon unit didn’t have the means of recording every minute.

Though I was outside the area of totality I still experienced the classic eclipse effects: the birds singing before going silent, reduced warmth of the sun and a very strange and eerie ‘blue’ light that is cast over everything. I’ve not experienced anything like it since and only hope that the sky on March 20th is a bit clearer than it was 16 years ago.

It is impossible to know what the weather will be like on the day at this range though a look back through my records to 1981 reveals that weather conditions on March 20th, the Vernal equinox this year, can vary greatly. In 2003 a high of 17.5C was recorded with 6.9 hrs of sunshine. However, two years earlier, the temperature reached just 4C as 8.2mm of rain fell.

It seems the media is working itself up into a frenzy over the eclipse, talking up the possibility that the event will cause a power surge that could interrupt supplies across Europe. However, the fact that solar accounts for just 10% of Europe’s renewable energy would suggest that such hyperbole is similar to the hysteria over the Y2K ‘Millennium Bug’ that failed to materialise?

* I will be revisiting this blog after the eclipse has happened to post results from my AWS readings.

** There’s a full account of Luke Howard’s eclipse here