I’ve been doing these written winter forecasts for five years now but this year I’ve never seen such a spread of probabilities as to how winter may pan out. So, if by the end of reading this you are none the wiser, you’re not alone!
The mean temperature for winter 2017/18 is looking average overall with average precipitation. While that doesn’t sound exciting for anyone looking for colder weather and snow I think the figures mask frequent 3 or 4 day-long cold snaps from the Arctic interspersed with milder interludes from Atlantic incursions; typical characteristics of a pattern driven by the troposphere. For anything longer term we have to hope for a warming of the stratosphere, a sudden stratospheric warming over the Arctic, that downwells into the troposphere, reversing the general westerly circulation. We are overdue an ‘SSW’ event but, even if one were to happen, its effects wouldn’t be felt until much later in the winter.
The current cold snap follows the recent disruption of the polar vortex. The ‘displaced polar vortex’ regime seems to be becoming more common as the Arctic gets warmer and maintains more open water during winter. This leads to anomalous ridging over the Arctic, which results in a displaced or bifurcated vortex, which leads to somewhere in midlatitude getting persistent anomalous cold. There was very cold air around last year but the UK missed out; the heart of the cold plunging down far to our east with snow falling on beaches in Crete!
This week’s cold snap looks like it will be short lived though the ‘displaced vortex’ could be an early sign of yet another pattern transition in the troposphere. Looking at the latest model output it is uncertain how long the next polar vortex perturbation will be.
So, whether we see any cold, snow-worthy, air this winter is a lottery – though I think our chances are a lot better than they have been for the past 5 years.
Because October and November have been so dry I’ve had very little to work with in terms of stats to try to find if the current pattern is similar to previous autumns. Instead I’ve looked in depth at ENSO, QBO and local meteorological data.
The El Niño–Southern Oscillation (ENSO) is a periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean. It is forecast to be mildly negative (La Nina) over the coming winter. Many doubt whether it has an impact on our winter but there seems to be a connection with strong La Ninas and very mild winters. Because it is forecast to only be mildly negative it’s impact may be very small. I had a look at similar years were ENSO was -0.4 in September and came up with the following.
I also had a look the quasi-biennial oscillation (QBO), the quasiperiodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere. This produced the following table of probabilities.
Singularities / patterns
My traditional method of looking back for similar patterns of weather in the autumn produced this table.
So, considering all three tables together, would suggest, probably bizarrely given the cold start to this month, a rather mild December followed by an average January and February.
In terms of climatology November maxima, considering the 1981-2010 average, shows a steady fall until the 15th. And another steady fall to the 22nd before things level off. This would reflect the November singularities; St Martin’s Summer, between 15th and 21st, peaking on the 18th, occurs in 66 per cent of years. The Early December storms singularity can arrive this month, on the 24th, the air off the Atlantic raising the mean temperature.
The average rainfall graphic shows that downpour amounts are variable through the month. A tendency for dry weather around the 15th reflects the St Martin’s Summer singularity.
This graphic shows the average 9am air pressure in November since 2013.
This month marks the 30th anniversary of the Great Storm. Some 18 people were killed as winds gusting to nearly 100mph affected London and the South East. Around 15 million trees were lost with Sevenoaks in Kent losing six of its seven historic trees.
The rapid development of ‘Low M’ took forecasters by surprise, the favoured outcome was for the low to move up through Brittany, remaining in or to the south of the English Channel.
I was living in a fairly sheltered corner of the London borough of Havering in 1987. I remember heavy rain just before midnight, around three hours before the storm reached its height, was heavy enough to send water trickling into my room, thanks to an overflowing roof valley. I thought it strange that Michael Fish hadn’t mentioned its severity in his lunchtime forecast.
I was awoken around 3.30am by a loud crash. Looking out the window I saw two dustbins flying down the road. You could sense each gust building in strength – the next dislodged a roof tile, sending it crashing on to the family car. By this point my mum and sister had awoken, my sister swearing she could feel the whole house moving: Mum ordered us downstairs. By this point the power had gone off and we sat listening to a small battery-operated transistor radio. We listened to updates from BBC Radio London where, like most other people, nobody knew what the hell was going on. The storm continued and first light gradually revealed the damage in the garden – a couple of trees over and next-door’s shed on its side; nothing compared to the rest of the region. But the disruption meant I didn’t attend school that day.
The storm was obviously a weather nut’s dream, and following so close on the heels of the coldest January I can remember. John Hall, of Surrey, can remember the storm well: “I’m not normally a very heavy sleeper, but I somehow managed to sleep through the worst of it (in Cranleigh, then as now).
“It was still windy when I woke around 7 am, but presumably not nearly as much as it had been earlier. By some miracle we still had mains power, and it was only when I switched on the radio and there was no sign of Radio 4 that I realised that something was up. (I assume the transmitter must have been damaged.) I walked the half-mile to the centre of the village to get my morning paper and then to catch the bus to Guildford station for my journey to work.
“It was only then that I learnt from the newsagent that there were no papers and wouldn’t be any buses, as every road in and out of the village was blocked by fallen trees. So I went home, switched on the TV and learnt all about what had happened.”
Dave Cornwell, of Laindon, south Essex, said: “Quite exciting but scary for me at home in Laindon. I awoke probably around 3.00 am to the sound of a metal dustbin lid (remember those?) flying down the street.
“Things sounded pretty bad and my sixth sense told me this was no ordinary windy night. I got up and looked outside and there was stuff flying by and lots of strange noises. One was my plastic gutter blown down and banging against the side of the house. I can’t be certain of the timings but we awakened our two young daughters and took them downstairs as I was worried as they slept in a room with a flat roof dormer window and there was a tall brick chimney stack directly above it. I heard more crashing sounds which unfortunately turned out to be a couple of roof tiles landing on my car roof which was parked in the drive. Of course with no internet then I did what a lot of people did and tuned into the police FM radio network. This gave me a better realisation that it was serious as they were describing the carnage on the roads and all of the emergency calls they and the fire brigade were getting.
“At about 5.30am I ventured out into my driveway to see if there was any serious damage but the storm was still raging and I can honestly say I couldn’t stand up and was unable to keep my balance so went back indoors. I think the wind speed was probably over 100mph at this point being funneled down the side of the house which runs south-north.
“By 8.00 o’clock I was getting ready for work and although by then people were being advised to stay at home I worked in a fairly essential service so thought I would give it a try. I managed to get to East London but there was debris everywhere and I saw a car completely crushed by a one of many trees that were blocking some side roads.
“Another thing I noticed that evening was my south facing windows had a layer of salt on them which must have been blown in from the south coast 60 miles away. It was a sight I’ll never forget and to this day I don’t like strong winds (had a scary flight at Heathrow in a severe gale as well) and always get a nervous feeling if I hear the wind getting up. Probably the most dangerous weather I have experienced anywhere in my lifetime.”
Much has been written about the storm, a ‘once in 500 year event’, including this summary by the Met Office. There is also an excellent paper by Bob Prichard published in Weather. The synoptic charts below show how Low M develops from 1200 on the 15th to 1800 on the 16th.
Because of widespread power cuts many television viewers didn’t see this recording of ITV’s Good Morning Britain at the time of transmission. A round up of the immediate aftermath of the storm, including comments from Jack Scott, can be seen in this edition of Thames News.
The following Daily Weather Report was published by the London Weather Centre:
An intense, and almost certainly exceptional, depression crossed the coast of south Devon soon after midnight, moving quickly, and deepening rapidly, with a track across the Midlands and out towards the Humber Estuary, leaving the United Kingdom land area around 0700 hours.
Some very severe conditions due to storm force winds were generated around the southern and eastern flank of the low, with gusts from approximately 0200 hours well in excess of 70 knots, and reaching a peak in the period 0300 hours to 0700 hours, with gusts to 90 knots reported from Herstmonceux and St Catherine’s Point in the early hours, and similar value gusts from the Channel Islands. The very stormy conditions were accompanied by some heavy rain, this rain pushing into Scotland and parts of Northern Ireland after dawn.
Clearer weather, on westerly winds, swept across southern Britain, pushing the worst of the stormy winds away into the North Sea. During the afternoon the country settled down to a blustery westerly with some heavy and thundery showers developing in clusters, running especially into western and southern coastal regions and parts of southeast England.
Across Scotland and northern England the skies remained cloudy, with outbreaks of mostly light rain, but troughs enhanced the showers in the northwest later in the evening with heavy rain. It was a rather cold day in most places, although the temperatures were near normal in the southeast.
The storm remains the most severe I have experienced in this part of the UK. The Burns’ Day storm in 1990 brought severe gale force winds in the London area but the low pressure was centred much further north.
The first month of autumn continued in the same vein as the last month of summer .
The mean temperature finished 14.8C, 0.6C below average and very similar overall to September 2013.
Some 53.5mm of rainfall was recorded, 103% of the 1981-2010 average. Some 114 hours of sunshine were recorded, 81 per cent of average, so on the dull side.
Overall the month was typical for early autumn – though possibly felt more autumnal because it was around 3C cooler than September 2016 and much wetter and duller than that month.
As usual at this time of year there is already much speculation about how cold the coming winter may, or may not, be. Winter has arrived over Siberia and early season snow cover is predicted to increase over the next week. However, the factor of early snow over Siberia being a sign of a cold winter to come in NW Europe is is only one piece of the jigsaw and I have seen it proved wrong a few times.
Snow cover: 2/10/2017
Modelled snow cover: 9/10/2017
Summary for September 2017
Mean (1 minute) 14.4
Mean (min+max) 14.8
Mean Minimum 10.7
Mean Maximum 18.9
Minimum 5.3 day 21
Maximum 22.7 day 04
Highest Minimum 16.7 day 04
Lowest Maximum 15.2 day 19
Air frosts 0
Total for month 53.5
Wettest day 16.1 day 27
High rain rate 16.1 day 13
Rain days 19
Dry days 11
Highest Gust 28.9 day 12
Average Speed 2.3
Wind Run 1670.8 miles
Gale days 0
Maximum 1022.7 day 01
Minimum 989.1 day 12
The 8th and 9th of August 2017 has produced probably the most miserable weather of this summer.
A rainfall event that began just after 8am on the 9th deposited nearly 36mm of rain in the Wanstead area over 14 hours.
The 09-09 total of 33.7mm made it the fourth greatest daily August rainfall since 1960.
The heaviest rain fell in a fairly narrow band, as shown by the official 24hr totals on ogimet.com. The low pressure system also produced a lot of rain for the east coast in the previous 24hrs with Bridlington recording over 56mm.
The rain brings the summer total to 207.7mm, just 0.6mm short of the amount recorded in 1997. Though it has been wet it is still a long way short of the wettest summer on record: some 391mm were recorded here in 1903.
In terms of temperature it has been a chilly start to August; the mean temp currently stands 1.2C below the whole month average. Considering CET it has been the coldest start to the month for 30 years.
July 2017 was the wettest since 1960. Some 92.3mm of rain were recorded which is 212 per cent of the 1981-2010 average.
Although the opening third of the month saw a continuation of the June heatwave temperatures gradually returned to normal values to leave the mean for the month at 19.2C, that’s 0.7C above average.
With all the rain sunshine totals were down. Some 167 hours were recorded, that’s 87% of average.
Though the rainfall total was impressive it is well short of the record of 164.2mm set in 1834, and is only 35th in the list going back to 1797.
Summary for July 2017
Mean (1 minute) 18.9
Mean (min+max) 19.2
Mean Minimum 14.7
Mean Maximum 23.7
Minimum 9.4 day 12
Maximum 30.5 day 07
Highest Minimum 18.3 day 06
Lowest Maximum 19.0 day 24
Air frosts 0
Total for month 92.3
Wettest day 30.8 day 11
High rain rate 56.4 day 29
Rain days 10
Dry days 21
Highest Gust 17.4 day 27
Average Speed 2.9
Wind Run 2163.5 miles
Gale days 0
Maximum 1024.2 day 16
Minimum 996.8 day 31
Total hours of sunshine 167
In terms of the rest of the summer a look at the ECMWF control run out to 10 days suggests an unsettled start to August with the jetstream centred right over the top of the UK. Things may improve as the Azores high attempts to exert more influence – so perhaps more in the way of sunshine than of late. In terms of heatwaves it is impossible to tell at this range.
1st: Cloudy but with sunny spells developing, these growing longer in length by evening.
2nd: Sunny with just a few light cumulus.
3rd: Sunny start though with plenty of cloud around, this tending to thicken after lunch with odd spot of rain.
4th: Sunny and very warm early then tended to cloud over before sun returned in the late afternoon and evening. Some very unstable low to mid level cloud.
5th: Sunny with just a few cirro-cumulus. Feeling very warm with cloud bubbling up in the evening, however forecast storms failed to materialise.
6th: Sunny with cirrus and dotted cumulus. This tended to thicken late morning though sun stayed out and became hot and humid.
7th: Sunny with lots of high-level cirrus and cumulus most of the day.
8th: Bright but mostly cloudy start, the cloud tending to vary through the day. Sunny after 4pm. Warm overnight.
9th: Bright but mostly cloudy start, the cloud tending to break and vary through the day.
10th: A mostly sunny morning and lunchtime until 2pm when it clouded over.
11th: Cloudy with some bright breaks at first. Cloud thickening with rain by noon, this falling sporadically before getting going after 5pm and stopping by 3am.
12th: Cloudy, damp and close start.
13th: Sunny with variable cloud until noon when there were just bright spells.
14th: Cloudy but with a few breaks around mid morning. Turning cloudy again before sunny spells in the evening.
15th: Cloudy with some sporadic rain as warm front blew through and close. Very limited brightness.
16th: Cloudy with some bright spells. Feeling warm and humid.
17th:Sunny with just a few cirrus drifting around. Feeling hot, cloud thickened from the west in the late afternoon.
18th: Sunny with variable cirrus and cirro cumulus through the day. Feeling very warm. Storms began building with supercell to west of London and over Chilterns.
19th: Cloudy, dull start and very humid with heavy mist – the cloud tended to lift to give sunny spells in the afternoon.
20th: Drizzle after shower before obs time, then showers through to 1pm.
21st: Cloudy start but with sunny spells developing. Clouded over in evening with intermittent heavy rain at 11pm and through the early hours.
22nd: Cloudy but with sunny intervals developing around noon. Heavy showers developing with thunder at 2.30pm and 3.07pm.
23rd: Bright with variable cloud
24th: Cloudy with light, showery rain from northerly airstream that originated in the Med.
25th: Cloudy with light rain just after obs time.
26th: Cloudy with occasionally rain. Feeling warm and a late clearance. Breezy and chilly overnight.
27th: Cloudy but bright and sunny spells developing. A very heavy shower at 1pm.
28th: Bright start but clouding over.
29th: Sunny start with cloud increasing after noon to leave overcast before patchy rain moved in. This falling more heavily at 5pm before clearing to further showers. More rain overnight before a strong squall arrived at 2.45am and lasted an hour with further bursts of rain through the night – two claps of thunder and lightening during squall.
30th: Sunny with variable cloud through the day. Very warm in the sunshine
31st: Sunny with variable cloud throughout the day.
I’ve seen this phrase uttered more than once over the past couple of days thanks to high temperatures and humidity. But ask anyone to define a hot day and you’ll get a different answer every time.
Growing up in the 1970s / 80s redtop newspapers would use the phrase once the mercury was nudging 80F (26.7C). But to ‘scorch’ you need sunshine, preferably at least 10 hours of it. Considering statistics from the Heathrow airport climate station in west London there have been 463 scorchers since 1959, the most recent happening on July 5th with 29.5C recorded and 13.9 hours of sunshine. There have now been 9 scorchers this year, already matching the number that were recorded in 2014 and only 3 short of last year.
But even with last month’s heatwave this year has some way to go, however, to match the amount measured in 1976 and 1995: 31 days!
The mean temperature for the month finished at 18.9C, that’s 2.8C above average. It was the second warmest June in a local record going back to 1797. Though it was only 0.4C cooler than 1976 it was also much wetter than that very dry month.
Though it appeared a wet month, over two-thirds of the recorded rain fell in two episodes.
Sunshine for the month was 202.3hrs, 114% of average.
In terms of the rest of the summer you would be forgiven for thinking that we have already had more than our fair share of good weather. One way of looking at it is to count the number of days the mercury rises above 25C with 10 hrs of sunshine. Since May that has happened on 13 occasions – far higher than anything in the past four years.
It will be interesting to see if July and August, normally the months where we get most of our summery weather are as good as June.
1st: Sunny with scattered cumulus through the morning, the cloud thicker during the day.
2nd: Cloudy start though brightening up with long sunny spells. Cloud bubbled up and a heavy thunderstorm moved in at 3.15pm and lasted an hour. Sunny again by 6pm.
3rd: Bright start with decreasing cloud.
4th: Sunny start though cloud bubbling up late morning into early afternoon. Cloudy and breezy with a few spots of rain at dusk.
5th: Cloudy and very breezy start. Bright at times.
6th: Rain and very windy to start with gale force 9 in Channel. Rain lasted into the early afternoon before clearing to bright spells. Odd shower overnight but remained blustery with a few trees down. Flowering cherry fell at mum’s at 6.30pm.
7th: Sunny with long sunny spells. An area of rain after dark then overcast through the night.
8th: Cloudy and breezy, a shower at noon and some bright spells at 1pm.
9th: Sunny though breezy with lots of cloud. Spots of rain in the wind.
10th: Sunny and warm start with lots of sunshine. Very breezy.
11h: Sunny and feeling very humid but breezy. Alternating between very warm sunshine and cloud. Very brief few drops of rain at dusk then mostly cloudy night.
12th: Sunny periods throughout the day. Cloudier at times. Clear overnight with warm, sunny start.
13th: Sunny, clear start and feeling warm early.
14th: Sunny most of the day with odd cumulus. Very warm though turning a bit fresher overnight.
15th: Sunny morning though with more cloud than yesterday. A fresh breeze developing.
16th: Sunny with variable cloud. Warm.
17th: Sunny though lots of hazy cumulus.
18th: Sunny though much cloud amid the humidity. Felt airless with only limited breeze. Oppressive overnight.
19th: Sunny with cloud decreasing
20th: Bright start though cloud breaking at 11am to leave clear afternoon with just a couple of cumulus.
21st: Sunny and hot all day with patchy cirrus. Warmest June day since 1976 at Heathrow 33.9C. Warm overnight but more of a breeze. Sunny early.
22nd: Very brief rain shower at obs time then sunny intervals. Cooler but still humid. Very breezy overnight.
23rd: Long sunny spells with hazy cumulus. Although cooler still hot in the sunshine. Cooler overnight and breezy.
24th: Mostly cloudy though bright. A sharp shower in the evening.
25th: Bright though mostly cloudy. A couple of bursts of drizzle but then sunny spells late evening.
26th: Sunny with lots of cirrus, cirrocumlus and a fallstreak hole in the sky. Warm but low humidity.
27th Sunny start though sun becoming scarce. Patchy light rain at 10.30am and thunder then a heavy shower at 3.45pm. Rain in the evening that lasted into the early hours.
28th: Cloudy and very dull at times with very light drizzle. Humid.
29th: Cloudy though bright with some sunny intervals.
30th Sunny though with lots of cloud. Decreasing cloud in the afternoon and a pleasant evening.