Category Archives: weatherlore

The same old weather every year?

Recurring weather patterns at certain times of the year are well known. The ‘Buchan Cold Spell’, ‘European Monsoon’ and Indian / St Martin’s Summer are all phenomena that have been studied extensively.

An article by the late meteorologist and broadcaster Philip Eden a number of years ago considered many of these patterns and found that, to varying degrees of reliability, they provided a guide to what the weather would be like at any given time of the year.

Considering climate change I wondered how much these patterns could still be relied on. Using my own pressure, rainfall and ‘wind run’ data (the total amount of daily wind) going back to the start of 2013 I had a look at the singularities for January and February

January patterns at the beginning, middle and end of the month appear to be the most reliable. However, it is only the ‘mid-Jan settled’ period that is most reliable.

singulariuty

pressure
The pressure trace most notably shows a general rise from the 17th, the date of last week’s windstorm, consistent with the mid-January settled singularity.
rain
Though this year’s ‘settled’ January spell saw rain the past 5 years have seen mostly dry weather.
windrun
Very little wind has been recorded around January 20th for the past 5 years

The early Feb settled spell occurs with very low probability: just 56 per cent. And this year the pressure, according to the GFS model, plotted below by WXCharts.eu, is predicted to be around 1040mb by February 2!

out to feb 1

new gif
This animation of the GFS model shows the idea of the Iceland low, which drives our SW’ly type weather, ‘taking a holiday’ to southern Iberia, possibly advecting any cold weather in the east to flood the UK

Looking at the results of the past 5 years it could be concluded that the patterns do still occur but because of the nature of the jet stream, which seems to meander far more readily than in the past, these stormy / quiet episodes are becoming shorter than they were in previous studies.

 

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Murphy’s winter and weather prophets

It is 180 years ago this month that Patrick Murphy shot to fame after successfully predicting one of the coldest Januaries on record.

murphy
anon, “The Modern Phenomenon of a Murphy the Gullcatcher of 1838” London Saturday Journal

The month, which had started mild, completely changed during the weekend of the 8th as a SE’ly wind set in. Hard frosts and snow became a daily feature with considerable falls across Scotland, disrupting mail and causing hardship for people and livestock.

By the 20th some of the lowest temperatures of the 19th century were recorded in London. At Greenwich -16C (-11C at midday) was reported at sunrise, while Blackheath saw -20C and Beckenham -26C. By the 27th the Thames at Greenwich was completely covered with ice at high water and elsewhere in the estuary ice floes were reported.

In some parts of northern Scotland, snow was noted to fall on most days between January 8th and May 3rd. Snow was also noted in upland areas of NE Scotland in June.

‘Murphy’s Winter’ as it became known made the astrologer from Cork a small fortune from the sale of an almanac, the contents of which also successfully listed the actual date when the frost would be at its most severe.

It was possibly the first long-range weather prediction that people through the ages seem to love, whether they are right or wrong.

Many characters have emerged over the years. Yorkshire’s Bill Foggitt, who used natural signals and animal behaviour during the previous autumn, was popular in the 1980s especially when he made a prediction of a harsh winter.

Others, including the Daily Express, who probably shouldn’t be mentioned in the same breath as Foggitt, are more about the clicks they hope to generate for their publishers than any earnest attempt at being right.

  • The mean temperature locally in January 1838 was -1.5C, the second coldest January in a series going back to 1797, and as cold as January 1963.
  • mean

 

 

Ophelia and mid-October storm trends

There is much anticipation in meteorological circles about the possible track of a deep depression spinning up the west coast of Ireland early next week.

The National Hurricane Center in Miami, on the 12Z GM run, puts Ireland and south-west England in the firing line of Ophelia.orphelia

The timing of the depression, coinciding with the 30th anniversary of the Great Storm, is remarkable and I wondered if there were other similar Atlantic storms through history.

A search through Martin Rowley’s excellent weather history site revealed that in October 1886, a small-scale but intense depression tracked ENE across central Ireland during the 15th, with lowest pressure estimated ~969mb.

16101886
The depression in October 1886 had a lowest pressure estimated ~969mb.

Gales, at least up to Storm Force 10, were reported by most ships and some coastal stations across the southern part of the British Isles, with ENE’ly gales across Scotland (north of the depression track). The low then moved slowly ESE to central-southern England (perhaps deepening a little) on the morning of the 16th, allowing N’ly gales (at least Storm 10) to affect the Hebrides.

Many trees were blown down across Ireland, the English Midlands and counties along the English Channel. Damage also occurred to standing crops, and the high winds were accompanied by heavy rain, which brought river flooding to England, Wales and Ireland, delaying the harvest, which was already compromised by the wet/windy weather. Some bridges were swept away.

14101881
October 14-15, 1881

Five years earlier, on October 14-15, 1881, an exceptionally severe gale (Force 9-10, locally Force 11) caused extensive damage across the British Isles & areas adjacent to the North Sea, especially along the north-east coast of England & across the eastern parts of the English Midlands.

Some 108 ships were reported missing. Inland, this gale was considered a ‘great storm’ with extensive loss of timber, especially in Scotland. One particular tragedy involved the destruction of almost the entire fishing fleet from the port of Eyemouth in Berwickshire.

The morning (14th) had been fine with near-calm wind. Some 41 vessels, mostly big deep-sea boats sailed out. In the middle of the day, the wind fell light, and then the storm struck suddenly. Nineteen of the boats were lost and 129 men failed to return to port.

 

The deadly hurricane of October 1817

Two hundred years ago this autumn a devastating hurricane ripped through the Caribbean. Thousands lost their lives as the winds destroyed hundreds of homes, ships and sugar plantations.

An account in Luke Howard’s The Climate of London reports the loss of 1,800 lives in Martinique alone during the storm that was the most destructive in at least 37 years.

One extract from a ship’s officer on November 30th, 1817, reports on the devastation seen on St Lucia: “We were struck with astonishment at the total change in the whole face of the country.

“We left it the day before the hurricane a beautiful rich green and every thing in a most flourishing state. It has now the appearance of a severe European winter. We went on shore of the 7th of November the scene of destruction which then presented itself is far beyond my power of description.

“On Pigeon Island three houses only are left standing out of nearly 259 the rest with the church are almost totally demolished.”

I have attached the entries below.

hurricane 1

hurricane 2

hurricane 3

Poor start to June? That’ll be the Euro monsoon

Widespread heavy rain and gales across the UK have made the start of summer feel very unseasonal. But the conditions, which follow an extended period of mostly dry weather, are very typical for early June.

june rainfall with record
The pattern for June over the past 10 years reveals the month often starts unsettled before drying up in the final week

The ‘NW European monsoon’ is one of the most reliable ‘singularities’ on the annual weather calendar. Though it sounds very unscientific that the atmosphere can remember how it behaved on a certain date in previous years much statistical work over the past 170 years highlight tendencies for unusual weather at particular times of the year. These tendencies were first identified by the German climatologist, A.Schmauss, in 1938.

While the pattern isn’t set in stone statistics show that the probability of the euro monsoon occurring between June 1st and 21st is 77 per cent.

GFS rain to 15th
The GFS operational run suggests an unsettled outlook

One of the most notable inclement spells of weather in June happened during the D-Day landings in 1944.

With the changes in ice at the North and South Poles, together with the massive positive temperature anomalies last winter,  it would be thought logical that this would have some bearing on the general pattern this year. But polar ice is only one variable to consider when trying to predict the world’s climate.

 

 

Is London heading for a hot summer?

Before I’m accused of going all Daily Express the following is based on winter statistics for the London area and other variables rather than the latest expert hopecast.

Even before looking at the data in depth the chart below shows that a warmer than average summer is more likely after a mild winter. The winter just gone was the third mildest in a record going back to 1797.

combined

There are some real corkers in that list, including 1995 when this area recorded the driest August on record. Other notable summers included 1990 – England in the semi-finals of the World Cup and another notably fine August: the then hottest UK temperature was set that year when a maximum of 37.1C was recorded at Cheltenham – a record that lasted until 2003. The year 1989 also stands out with a notably sunny summer.

So far, so good. But what about rainfall? Some 145mm of rain fell this winter – pretty much on the nose average for this region. Combining warm winters with similarly average rainfall gives the following list.

with similar rain

Though some years have disappeared there are still some decent summers, and notably sunny too. The year 1975 stands out as does the sunniest summer on record, 1911! Both were also very dry summers.

Altough the teleconnection with El Nino is tentative in our part of the world the winter seemed to follow the pattern of most positive ENSO episodes, so it is worth having a look to see where the data goes. The latest forecast by NOAA suggests:

A transition to ENSO-neutral is likely during late Northern Hemisphere spring or early summer 2016, with a possible transition to La Niña conditions during the fall.*

If the forecast goes to plan the second ‘rainfall list’ would narrow further:

Screen Shot 2016-03-08 at 02.44.05

Viewed by graph reveals that ENSO values of all the years decreased over the course of the year. Series 1 is 1998, series 2 is 1983 etc.

Screen Shot 2016-03-08 at 02.48.01

In conclusion, the results would suggest that there is a 66% chance of a decent summer with below average rainfall and above average sunshine. In terms of details June 1st is still a very long off in meteorological terms – so whether it includes any heatwaves that would put it my premier league of hot spells is anyone’s guess at this range.

If it’s anything like 1959, 1975, 1983 or 1998, however, I think most folk will be happy.

*The above contradicts some forecasts which suggest a continuation of the general pattern that persisted during the winter: warm SSTs in the Atlantic / warm water south of the Grand Banks were largely responsible for the cyclonic westerly type of weather that caused the mild weather. In summer this would cause changeable weather rather than long spells of settled weather.

 

Fading faith in St Swithin

Legend has it that the weather on Wednesday will be the same for the next 40 days.

St Swithin’s day, if thou dost rain,
For forty days it will remain;
St Swithin’s day, if thou be fair,
For forty days ’twill rain na mair.

St Swithin’s Day is probably among the most well known of weather folklore – but, taken at face value, it is probably the most unreliable.

Grasslands around Wanstead Park have gradually turned brown because of the lack of rainfall since March
Grasslands around Wanstead Park have gradually turned brown because of the lack of rainfall since March

Since 1848 Wanstead and the surrounding region has enjoyed 93 dry St Swithin’s Days (56%). From these the longest dry spell that followed was just 18 days, in 2000. On average, if St Swithin’s is dry, the weather stays fair for 3 days, with rain arriving on the 18th. Many dry St Swithin’s Days (17%) are followed by rain the next day – these results skew the median for rain after a dry St Swithin’s to just 2 days!

Another interesting observation is that the 40-day period that followed a dry St Swithin’s is on average 13% WETTER than if it rained on July 15th.

So what does this mean for the rest of July and the summer? Looking back at other years that have seen a mostly dry and warm pattern in the run up to St Swithin’s Day we should see a continuation of frequently dry, warm and sunny conditions, interspersed with rainy days and, perhaps, thundery breakdowns. A typical British summer!

Putting superstition and singularities aside current weather models back this up.

St Swithun's reputation as a weather saint is said to have arisen from the translation of his body from a lowly grave to its golden shrine within Winchester cathedral, having been delayed by incessant rain for 40 days
St Swithin’s reputation as a weather saint is said to have arisen from the translation of his body from a lowly grave to its golden shrine within Winchester cathedral, having been delayed by incessant rain for 40 days

St Swithin was born around 800AD and died on July 2, 862, at Winchester, Hampshire. According to historians he was fond of building churches in places where there were none. St Swithin, who was bishop of Winchester, was buried in the churchyard of the Old Minster at Winchester, where passers by might tread on his grave and where the rain from the eaves might fall on it.

His reputation as a weather saint is said to have arisen from the translation of his body from this lowly grave to its golden shrine within the cathedral, having been delayed by incessant rain for 40 days.

The basis of the St Swithin’s saying follows the fact that by July 15th summer weather patterns are already well established and tend to persist through the coming weeks.

In meterological terms the position of the frontal zone around the end of June to early July, indicated by the position of the jet stream, determines the general weather patterns (hot, cold, dry, wet) for the rest of the summer. Like a little stream in its bed, the frontal zone tends to ‘dig in’ shortly after the summer solstice.

As the path of our weather systems is controlled by the jet stream, a more southerly location of the frontal zone – as happened last year – is likely to bring unsettled, wet and cool weather. On the other hand, a frontal zone shifted further to the north – as is happening this year – will help the Azores high to build over western Europe, thus bringing dry and pleasant weather to the UK.

Other western European countries also have similar St Swithin’s day sayings – that follow the principle rule. In France they say ‘Quand il pleut a la Saint Gervais Il pleut quarante jours apres’ – If it rains on St. Gervais’ day (July 19th), it will rain for fourty days afterward.
In Germany the Siebenschlaefer or seven sleepers day (July 7th, after the Gregorian calendar) refers to the weather patterns of the following seven weeks.

Spring signs for a dry summer?

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.

Weatherlore: Colin Finch’s 38F rule

Signals for winter have always been well reported by the media. Back in the 1980s weather anoraks across Britain would wait with bated breath to read Bill Foggitt‘s latest prognostications for the coming winter. Though Foggitt had some success his observations, among other weather ‘gurus’, often amounted to weatherlore that has only a slightly greater than evens chance of being right.

One popular myth is that very large blackberries mean a harsh winter. The fact that this has more to do with plentiful rainfall plumping up the fruit at harvest time is ignored.

Colin Finch’s 38F minus rule is altogether different and provides a very good guide to the kind of weather we can expect in January and February. For the rule to work the maximum temperature must be 38F (3.3C) or less for four consecutive days before Christmas Day.

finchColin, an amateur meteorologist who passed away in 1991, spent much time researching his rule in the 1970s. He found that most of the coldest winters since the end of the second world war gave a hint of things to come in the weeks leading up to Christmas: the Decembers of 1946, 1955, 1962, 1968, 1969, 1978 were all followed by cold late winters. In 1984 and 1985 the cold spell arrived at Christmas. Other years to loosely follow the rule, 1986, and 1990.

A few weeks ago I was reminded about Colin’s findings and decided to have another look, using daily record data for this area stretching back to 1806.

The results were surprising. If there is a run of cold days (3.3C or less) around mid-month the chance of an average to colder than average January and February is 94% and 74% respectively. The chance of an average to colder than average March is 96%. Also notable is that the chance of a severe spell in January (4C colder than normal) is 30%.

So much for the figures. What are the chances of a run of cold days between now and Christmas Day?

Sunset Southwark Bridge
Sunset Southwark Bridge

Up until this week the weather has been fairly quiet with little rain and cold, often frosty nights. But westerlies are now roaring back in from the Atlantic and could be a hint of what is likely to prevail later in the winter. However, the ‘crunch’ time for the 38F minus rule comes soon after the middle of the month. If a spell of Arctic weather develops at that time, even if it lasts only a few days, then the chances of a major cold spell after Christmas are much higher.

As I write this blog the models suggest that a run of cold days may just be possible. It is also notable that the likelihood of a sudden stratospheric warming event, argued by many to be a precursor for conditions that would favour the development of a cold spell, is increasing with a peak set for mid January.

We’ll see but Colin Finch’s findings all those years ago are fascinating and are still relevant today.

My method in using the rule can be found here.

Statistics on the rule can be found here.

* The following obituary appeared in an edition of Weather magazine, a publication of the Royal Meteorological Society, in 1991.

“Colin Finch – The news of the sudden death of Colin Finch on Friday, 23 August 1991 at the tragically early age of 55 will be received with sadness by Members of the society and readers of Weather.

There is no doubt that Colin was one of the most enthusiastic amateur meteorologists that the Society has ever had and, without seeking publicity for himself, he was responsible for making many other amateur enthusiasts aware of the Society and encouraging them to join.

Colin’s interest in the weather began when he was a small boy and received a considerable boost during the snowy and very cold winter of 1946/47 when he was 10 years old. In 1949, at the age of 13, he began to take regular temperature and rainfall readings and gradually added more sophisticated equipment. His record of daily weather data was unbroken until July 1991 when he became too ill to continue.

When he left school in 1953 he joined the Meteorological Office as a Scientific Assistant at Kingsway and was trained under the keen eye of Dick Ogden. Later, after a spell at Heathrow Airport, he left the Office frustrated by his inability to develop a career because he didn’t have sufficiently good educational qualifications. Instead, he turned to a successful business career but his enthusiasm for weather observing and forecasting increased.

Each day he plotted and analysed synoptic charts compiled from short-wave Morse code transmissions which he took down by hand. In the 1960s and 1970s it was quite normal for him to spend Saturdays plotting a chart for the whole of the Northern Hemisphere from Morse broadcasts. Later he had facsimile and satellite-receiving equipment installed at home.

By the late 1960s he was liaising with local authorities and the police in Surrey, warning them of the likelihood of severe weather events. In 1970 he joined the then newly introduced BBC Radio London and every Friday morning he would discuss current weather events and give climatological background data about the week ahead. For these broadcasts he would get up in the early hours to plot a synoptic chart before he went to the studio.

After the broadcasts he would go to the City for a normal day’s work. He kept up this punishing schedule for several years. When the Society introduced the highly successful one-day Saturday discussion meetings in September 1972 Colin was one of the first amateur meteorologists to give a presentation and he was a regular contributor to these occasions. He was an imposing figure, 6ft 4in tall, and was easy to seek out at meetings.”

A dry or wet St Swithun’s?

St Swithun's reputation as a weather saint is said to have arisen from the translation of his body from a lowly grave to its golden shrine within Winchester cathedral, having been delayed by incessant rain for 40 days
St Swithun’s reputation as a weather saint is said to have arisen from the translation of his body from a lowly grave to its golden shrine within Winchester cathedral, having been delayed by incessant rain for 40 days

Legend has it that the weather on Tuesday will be the same for the next 40 days.

St Swithun’s day, if thou dost rain,
For forty days it will remain;
St Swithun’s day, if thou be fair,
For forty days ’twill rain na mair.

St Swithun’s Day is probably among the most well known of weather folklore – but, taken at face value, it is probably the most unreliable.

Since 1961 Wanstead has enjoyed 30 dry St Swithun’s Days (57%). From these the longest dry spell that followed was just 18 days, in 2000. On average, if St Swithun’s is dry, the weather stays fair for five days, with rain arriving on the 20th.

Another interesting observation is that the 40-day period that followed a dry St Swithun’s is on average 13% WETTER than if it rained on July 15th.

So what does this mean for the rest of July and the summer? Looking back at other years that have seen a mostly dry and warm pattern in the run up to St Swithun’s Day we should see a continuation of the mostly dry, warm and sunny conditions, perhaps with frequent thundery breakdowns, the first arriving on Thursday into Friday.

Putting superstition and singularities aside current weather models back this up.

Featured Image -- 1745St Swithun was born around 800AD and died on July 2, 862, at Winchester, Hampshire. According to historians he was fond of building churches in places where there were none. St Swithun, who was bishop of Winchester, was buried in the churchyard of the Old Minster at Winchester, where passers by might tread on his grave and where the rain from the eaves might fall on it.

His reputation as a weather saint is said to have arisen from the translation of his body from this lowly grave to its golden shrine within the cathedral, having been delayed by incessant rain for 40 days.

The basis of the St Swithun’s saying follows the fact that by July 15th summer weather patterns are already well established and tend to persist through the coming weeks.

In meterological terms the position of the frontal zone around the end of June to early July, indicated by the position of the jet stream, determines the general weather patterns (hot, cold, dry, wet) for the rest of the summer. Like a little stream in its bed, the frontal zone tends to ‘dig in’ shortly after the summer solstice.

As the path of our weather systems is controlled by the jet stream, a more southerly location of the frontal zone – as happened last year – is likely to bring unsettled, wet and cool weather. On the other hand, a frontal zone shifted further to the north – as is happening this year – will help the Azores high to build over western Europe, thus bringing dry and pleasant weather to the UK.

Other western European countries also have similar St Swithun’s day sayings – that follow the principle rule. In France they say ‘Quand il pleut a la Saint Gervais Il pleut quarante jours apres’ – If it rains on St. Gervais’ day (July 19th), it will rain for fourty days afterward.
In Germany the Siebenschlaefer or seven sleepers day (July 7th, after the Gregorian calendar) refers to the weather patterns of the following seven weeks.