October is one of those months that can see both ends of the spectrum; from calm ‘mists and mellow fruitfulness’ and, rarely, frost, to wet and wild systems whistling in off the Atlantic, best known being the 1987 Great Storm and, more recently, the St Jude storm.
I’ve put together a few top 10s of stats for Wanstead, St James’s Park and Heathrow for the month of October.
Some national UK October values according to TORRO
In terms of climatology October maxima, considering the 1981-2010 average, shows a through the month, though around there is often a spike. This would reflect the October singularities; early October storms, between 5th and 12th, peaking on the 9th, occur in 67 per cent of years. St Luke’s summer, between 16th and 20th, peaking on 19th, also has a 67 per cent probability. If you look at the graph there is a spike just after the 19th.
Mid-autumn storms occur between 24th and 29th October, with a 100% probability.
The average rainfall graphic shows that downpour amounts are variable through the month. A tendency for dry weather around the 17th and 18th before the wettest days on the 20th and 21st.
Wild weather in the run up to the autumnal equinox was frequently a staple of the Septembers of my childhood but it has been absent in recent years.
Since 2013 I have been recording the ‘wind run’ data on my AWS, a stat generated by the amount of times the anemometer spins.
The results show there has been nearly two-and-a-half times more wind than the 5-year average.
Stormy weather over the equinox is one of the less frequent recurring singularities. The meteorologist Philip Eden a few years ago noted that ‘Mid-September storms’ during the period of 17th to 24th September had a frequency of 60 per cent.
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.
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!
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.
It is 180 years ago this month that Patrick Murphy shot to fame after successfully predicting one of the coldest Januaries on record.
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.
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.
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.
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.
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.
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.”
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.
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.
24hr rainfall totals
Depression across the UK
One of the most notable inclement spells of weather in June happened during the D-Day landings in 1944.
0100 June 5 1944
12 June 6 2017
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.
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.
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.
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:
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.
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.
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.
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 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.
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.
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.