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

London droughts back to 1871

As we enter the second week of July most local readers of this blog will not be surprised that we have been in drought conditions for over a month.

Top 30 individual droughts 1871-2018There are many descriptions of drought but the one I am using here, for sheer simplicity of comparison back to 1871, is the definition used up until the 1990s; that is 15 consecutive days with less than 0.25mm (0.01 inches) rain on any one day.

Meteorological droughts occur in most years though obviously ones that occur in summer are far more noticeable than those in winter. Since 1871 there have been 35 calendar years where no drought has taken place.

The longest drought, probably not surprising for those who remember it, occurred during the long hot summer of 1976. The fact that summer came on top of a very dry winter, rainfall that season was about a third of what was recorded here last winter, meant that water supplies were in a much worse state, with hosepipe bans common.

Other drought years to feature include 1959, which saw the 3rd sunniest summer on record, 1929 and 1995, a summer which saw one of the hottest heatwaves on record.

For the stats I’ve used local rainfall figures back to 1959 and then stats used at Kew to 1871.

individual droughts
This graphic shows droughts were most common between 2000 and 1921. Apart from this year the length of droughts seems to be declining

Looking at the results more closely I’ve divided them into their meteorological seasons.

spring drought

summer drought

autumn drought

winter drought

 

 

 

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London’s July extremes since 1959

With the ultra dry and warm month of June many feel the rest of summer will remain hot and dry. Recent weather patterns have seen much high pressure to our north keeping us dry and mostly sunny but protected from any humid Spanish plumes.

A look at local east London stats shows that half of the last 10 July months have been warmer than average while only two have been much drier than average.

I’ve put together a few top 10s of stats for Wanstead, St James’s Park and Heathrow for the month of July.

july1959WAN

july heathrow

sjp july

Some national UK July values according to TORRO

 

Hottest: 19th 2006: 36.5C at Wisley, Surrey.
Coldest: 15th 1977: -2.5C at Lagganlia, Highland.
Wettest: 18th 1955: 279.4.8mm at Martinstown Dorset.

july av mxIn terms of climatology July maxima, considering the 1981-2010 average, shows a fairly steady increase through the month, though around the 17th there is often a dip before a warm end. This would reflect the July heatwave singularity which occurs every year at 80 per cent probability.

The average rainfall graphic shows that downpour amounts are fairly random from year to year. The driest days are the 1st and the 25th. july av rn

 

June 2018: driest on record since 1797

This June will probably be most remembered for the lack of rainfall throughout the month. I recorded just 0.7mm of rain over the 30 days – the driest June in a local record going back to 1797, 0.4mm less than the previous driest June in 1925.

fire
A fire on Wanstead Flats on Friday 29th was quickly extinguished thanks to the fire brigade

As I write this the area is now experiencing its 24th day of ‘meteorological drought’ conditions with little prospect of anything heavy anytime soon. The month was in stark contrast to May which saw may downpours associated with thunderstorms.

It was a warm month. The mean temperature finished 18.1C, exactly 2C above average, though slightly down on last June and the 7th= warmest since 1797.

Some 231.4hrs of sunshine were recorded, 130 per cent of average, making it the sunniest May for 8 years, and the 30th sunniest since 1881.

The warmest day occurred on the 25th with 30C.

The wettest day occurred on the 9th with 0.4mm falling.

Summary for June 2018

Temperature (°C):
Mean (1 minute)  17.7
Mean (min+max)   18.0
Mean Minimum     12.3
Mean Maximum     23.8
Minimum          6.4 day 12
Maximum          30.0 day 25
Highest Minimum  17.8 day 18
Lowest Maximum   17.9 day 04
Air frosts       0
Rainfall (mm):
Total for month  0.7
Wettest day      0.4 day 09
High rain rate   4.0 day 09
Rain days        1
Dry days         29
Wind (mph):
Highest Gust     18.3 day 14
Average Speed    3.1
Wind Run         2199.7 miles
Gale days        0
Pressure (mb):
Maximum          1029.9 day 21
Minimum          1008.2 day 14
Days with snow falling         0
Days with snow lying at 0900   0
Total hours of sunshine        231.4
Elsewhere in the UK it has been a very dry month across England.
0-25
Two CET stations, Rothamsted and Pershore recorded 2.2mm and 10mm respectively.
Other stations:
Northolt 0.8mm
St Bees Head: 25.2mm
Scilly: 7.6mm
Shoebury: 0mm

 

Wild swimming in Wanstead Park?

Lewisham’s Beckenham Place Park will next year be home to a new wild swimming lake, thanks to a plan to make London the world’s first National Park City.lewisham pool

The scheme put me in mind of the Shoulder of Mutton lake in Wanstead Park which, decades ago, used to host swimming galas and other events. Long-time residents of Aldersbrook will remember the jetty and diving board that stood at the edge of the lake before falling into disrepair that led to their removal.

With millions set to be spent shoring up the dams of the park’s lake system it is surely feasible that the City of London Corporation can reopen Shoulder of Mutton to swimming while the work is undertaken.

While being cheaper than a lido it would provide an excellent resource and give local residents the chance to enjoy once more swimming in natural surroundings, just like in the Serpentine and Hampstead Ponds.

beach
The Shoulder of Mutton pond has a natural beach and once hosted swimming galas and diving competitions

 

Landing at Skiathos island

I took this short video during approach and landing at Alexandros Papadiamantis airport, Skiathos, in August 2016.

As you can see the weather was sunny, around 32C with light winds. Because of the short runway if the weather is less than perfect airliners sometimes get diverted to the mainland, necessitating a ferry crossing – though, in four years of visiting, I’ve only had one unscheduled stop on departure – if the plane is full the aircraft can only be partly filled with fuel.

The spectacle of jets landing has also become a must do for tourists who stand at the end of the runway waiting to get blasted during close encounters with landing aircraft.

It’s a beautiful island in the Sporades and was where, along with Skopelos, provided the backdrop to the film Mamma Mia! Because it is very green I’ve found it doesn’t get overly hot like other parts of Greece.

Indeed, in all the years we’ve visited there has always been one stormy day before the weather clears again.

 

London’s June extremes since 1959

With the recent warms months of April and May you’d be forgiven for thinking that we’re in for a hot summer. Indeed the recent pattern of weather, would it repeat over the next month, could see many maxima records tumbling.

A look at local east London stats shows that six of the last 10 Junes have been warmer than average while half have been much drier than average.

I’ve put together a few top 10s of stats for Wanstead, St James’s Park and Heathrow for the month of June.

Probably most notable from the below values is that recent Junes have been devoid of extreme cool temperatures and rainfall.

Snow has been known to fall in June, in 1975.

Rain is usually most frequent in the last week of the month.

june extremes wans

heathrow june

june sjp

The 10 driest Junes were:

 

Some UK May values according to TORRO

Hottest: 29th 1957: 35.6C at Camden Square, London. Also Southampton 28th 1976
Coldest: 9th 1955: -5.6C at Dalwhinnie, Highland. Also June 1st and 3rd 1962: Santon Downham, Norfolk
Wettest: 28th 1917: 242.8mm at Bruton, Somerset

Screen Shot 2018-06-06 at 12.11.18In terms of climatology June maxima, considering the 1981-2010 average, shows a gradual increase through the month, though around the 19th to the 21st there is often a dip before a warm end. This would reflect the June Monsoon which occurs every year at 77 per cent probability.

The average rainfall graphic reflects this, showing a four-day wetter spell after the 20th.

Screen Shot 2018-06-06 at 12.29.10

 

 

 

 

May 2018: warmth and thunderstorms

This May will probably be most remembered for the number of thunderstorms affecting the area. I recorded an unprecedented (in my memory) four consecutive days of thunderstorms.

convection
Convective clouds build over Wanstead Flats

It was also warm with a couple of days making the top 10 of hottest days since 1959. The mean temperature finished 15.1C, 2C warmer than average, the warmest May for seven years and the 8th= warmest since 1797.

Rainfall at 65.5mm was 128 per cent of average and slightly drier than last year.

Some 244hrs of sunshine were recorded, 134 per cent of average, making it the sunniest May for 7 years, and the 11th sunniest since 1881.

Spring finished with a mean temp of 11C, 0.8C above average, 1C cooler than last year. Rainfall at 181.9mm, was 135 per cent of average, making it the wettest spring for 10 years. Sunshine of only 411.2 hours made it the dullest spring since 2006.

The warmest day occurred on the 7th with 28.1C.

The wettest day occurred on the 29th with 29.8mm falling during a prolonged thunderstorm.

Air frosts: 0, Ground frosts: 0

This summer in east London is looking average with little to write home about weatherwise.

Summary for May 2018

Temperature (°C):
Mean (1 minute)  14.7
Mean (min+max)   15.1
Mean Minimum     9.0
Mean Maximum     21.1
Minimum          1.8 day 02
Maximum          28.1 day 07
Highest Minimum  15.7 day 31
Lowest Maximum   14.1 day 02
Air frosts       0
Rainfall (mm):
Total for month  65.5
Wettest day      29.8 day 29
High rain rate   60.4 day 28
Rain days        9
Dry days         22
Wind (mph):
Highest Gust     20.6 day 02
Average Speed    2.4
Wind Run         1808.0 miles
Gale days        0
Pressure (mb):
Maximum          1027.4 day 16
Minimum          1001.5 day 02
Days with snow falling         0
Days with snow lying at 0900   0

 

 

 

 

Four 3000m Alpine peaks in four days

Climbing further into the cloud the silence was suddenly broken by what sounded like thunder. I soon realised that this distinctive noise echoing around the surrounding peaks was an avalanche that wasn’t that far away.

daubenhorn summit
The summit of the Daubenhorn, like many peaks, is marked by a cross

My guide, Davide, seemed unconcerned and as we closed in on the summit of the Daubenhorn, 1,500m above Leukerbad, the cloud started to thin. Two French tourers above us had roped up and were nearing the top as we stepped out of our skis and carefully continued on to the peak.

Just as I was edging close to a huge cornice Davide advised me that it would be a good idea to stop as should it have given way there would be little between me and a 1,500m plunge down a cliff through the mist into Leukerbad. Heights don’t usually phase me but there was something about peering down into that foggy abyss that felt even more un-nerving.

My four-day tour of Valais and Bernese Oberland started just over 24 hours previously at the Gemmi pass, 2,350m up. My first tracks were an icy traverse to the bottom of a wide snowfield; lack of experience on super light touring skis was evident as I wobbled all over the place on the bullet-hard early morning ice.

daubenhorn cornice

Crossing the high valley floor the early morning chill soon disappeared as the sun edged higher. My poor, laboured technique, together with my body being used to life at sea level, made the ascent a real slog.

As the angle of the path grew steeper I soon discovered another alpine touring tool to make life easier: ski crampons.
We advanced higher and I was mystified by Davide’s lack of thirst as I polished off the recommended 1.5L of water for a day’s tour before we made it to the foot of the Wildstrubel glacer; I was not in a good way.

wildstrubel summitI soon forgot my predicament as I rounded a ridge and got my first glimpse of a glacier. About two thirds the way up the 3,200m Wildstrubel, however, mild altitude sickness started to kick in – the final 100m were a real effort. Advancing over the crest it was blowing a hoolie – Davide managed to capture the customary shot with Mont Blanc standing proud in the distance. The queasiness I felt below the summit was replaced by sheer elation of climbing a peak over 3,000m for the first time.

As we began our descent I was all over the place, my usual neat and tidy skiing style severely hampered by sheer exhaustion and pain in my feet.

lameur
Lammeurenhutte

It was a combination of downhill and skinning before we reached the Lammeurenhutte at 2,500m, the elation of this establishment appearing mirage-like over the brow of a hill was enough to spur me on to the finish.

The bright skies and good vis of earlier had now been replaced by thickening cloud and light snow. No matter. I collapsed onto a bench outside and watched as other tourers arrive and nonchalantly take off their skis and disappear inside. I’m left looking at my destroyed feet, the sorest they’ve ever been with a large blister on the inside of both heels.

Davide reappeared with some hut slippers, basically moulded ‘Crocs’, which are provided for tourers who refrain from carrying the extra weight of footwear.

bedAfter taking all the equipment inside we were showed to our ‘rooms’. Davide, as a guide, was allowed to stay free in the guides’ room while I’m shown to a bunkroom made up of beds with three mattresses side by side on two levels.

I fled to the dining room which was the only common area in the building. Davide was already seated with two large beers. We chatted about the day and possibilities for the Monday. There were a couple of hours to kill before dinner, like many huts a single sitting, which I spent coming to terms with my altitude discomfort.

An early night followed after a wholesome meal of lentil loaf and vegetables. There’s not much to do after dinner except read and, because everyone is exhausted from touring, the dining room empties well before the 10pm lights out. Despite my exhaustion it was a fairly restless sleep, no doubt caused by the altitude.

After a hearty breakfast we were back in our skis and descended 400m to the valley floor, over icy terrain, some of which passed some incredibly steep sections.

sfavalanche
Southern aspects were being stripped of snow by the strong sun

In milky, warm sunshine we began our ascent of the 2,950m Daubenhorn. The sun was taking its toll on south-facing slopes across the valley, whole sections of the pack started to rip away from the surface. After the bright start the weather started to close to close in again. And I had my first experience of being close to an avalanche.

Though the customary summit photo was shrouded in cloud the weather changed again for our descent – my ski legs finally seemed to be coming back but before I knew it we were back on the valley floor for the hour or so walk back to the top of the cable car that we last saw 24hrs previously.

Two German guys I met in the hut the previous night were waiting – they told me they’d abandoned efforts to climb Wildstrubel because of poor weather and seem impressed when I told them we’d bagged that and the Daubenhorn in reasonable weather.

Screen Shot 2018-06-02 at 23.22.56
The sheer rock face looking up to Gemmi pass

On disembarking the cable car it was evident that summer was fast approaching in the low valley – cascades of water could be seen running off the horseshoe of sheer cliffs, triggering mesmerising avalanches. I stared in wonder but the locals seemed to just take it in their stride: “Summer is coming!” said one.

Driving back from Leukerbad we began to discuss what the options would be for my final two days. One was to get the 4.30pm cable car from Saas Fee for another night in a hut. Another was to take the Jungfrau railway up to the summit to spend a night there. But both these options looked less attractive than a return to Chalet Isabel and a hot shower!

We settled on a very early start for Tuesday for a tour of the mountains above the Simplon Pass. I enjoyed a couple of hours of late afternoon sunshine on the terrace before dinner which, as the previous night, was a delicious three-course affair. Being alone I felt compelled to utter the usual: “Is there anything I can do?” despite the fact I’d paid for half board; I’ve never been one to lord it over others.

We discussed local politics, flora and fauna as well as the Davide’s wife Jennifer’s ties to the area and how they stretch back generations.

As with previous nights I retired to bed early as we had to be up at 4.30am for the 50 minute journey to Simplon. I told them not to bother with the cooked eggs and to go for the lightest of breakfasts as my stomach really can’t take the numerous hairpin bends at that time of the day.

We started off in pitch dark – I did my best to keep the conversation flowing at this ungodly hour. I noticed Davide listened intently to a news bulletin at the top of the hour – the announcer saying that extreme heat was expected: never good for avalanches.

After twisting our way upwards toward the pass we emerged from the tunnel and were suddenly confronted by a deer that seemed to jump out of nowhere from the side of the road. Davide managed to slam on the brakes; to swerve would have sent us careering into the path of the huge artic.

hospiz
The Simplon Hospiz

We were both now wide awake and within minutes were pulling into the car park of the hugely imposing Simplon Hospiz. Built in 1801 under decree by Napoleon this establishment, run by priests, has provided shelter and refreshment for tired souls who are halfway across the Alps for over 200 years.

We weren’t there for the hospitality, however, and Davide was quickly ushering me toward the side of the building where the path starts toward the Breithorn which, literally, translates as ‘wide mountain’. Desperate for the loo, however, I fled toward the hospiz for a toilet stop. I go inside and despite seeing corridors of rooms there is not a soul around. The deathly silence is quite unnerving and I am reminded of that scene in the horror film The Shining.

hubs
Davide skins toward the Hübschhorn

After leaving as quickly as possible we were soon back in bindings and skinning toward the Hübschhorn, a majestic ice-encrusted peak in front of the Breithorn. It was barely light and the first rays of sunshine were just beginning to strike peaks across the valley above Leuker. It was incredibly quiet, about half a dozen tourers had beaten us to it and were making speedy progress. Across the valley I could see one of the ski areas of the Bernese Oberland.

A couple of miles in the terrain began to steepen markedly; my progress became erratic and Davide called a halt to enable us to attach our ski crampons. As I fished about in my rucksack Davide rebuked: “This stuff should be on the top so it is easy to grab!” Second nature to seasoned tourers, I beat myself up about making such an elementary mistake. I never ‘gave it back’ to Davide as it is the safety of a client that is paramount: “If you go over here it is all the way down to the bottom.” I peered down the slope that was littered with huge chunks of snow from earlier avalanches. We pressed on and a sense of relief was evident once we cleared the avalanche zone. I was once more able to relax and take in the surroundings. As we reached a rocky outcrop a ptarmigan-like bird appeared but scarpered too quickly for a photo.

ridge
Two tourers appear on the ridge

We pushed on. By now I could feel my heels starting to rub again. Every time I saw a likely stopping place it was to no avail. We stopped briefly for a drink and snack but there is no time on these hikes to really kick back. Davide let it be known that he was worried about the time we were taking and that we might not reach the summit; I think the earlier news bulletin about possible record hot weather was playing on his mind.

We left hastily, I said I was willing to walk faster, not giving too much away that my heels were feeling sore again. With about 300m still to go Davide could see I was dropping back off the pace again. He offered to take some of the weight out of my pack – the water alone probably weighed a kilo or so.

dog
Just before the summit I became aware of a dog that was running uphill even faster than his master

For a brief moment I felt like somebody was lifting me up the mountain – though it was only a kilo the altitude has an exponential effect. Within 30 minutes, however, I was struggling again, and Davide, without argument, took my entire backpack. I’d usually protest but such was the pain in my heels I didn’t argue. To add insult to injury soon after I noticed a spaniel-type dog running upward in front of me, his master clad in lycra and pushing toward the summit using extra long sticks.

If anything seeing this guy virtually running toward the summit helped take my mind off my blistered heels.

We made it to the col de Briethorn, about 100m below the summit. “There is not much more to see at the top,” said Davide, as I stared at Italy in the distance in the valley below.

After a few pictures we adjusted our skis for the downhill leg. For the first time since my arrival I felt like I was getting my ski legs though such is the light weight of touring skis that it feels impossible to ‘feel’ as good as you can on normal downhill skis, the added weight making you more stable.

col
Col di Breithorn with Italy in the distance

In virtually no time we were back to the avalanche zone. The smooth terrain with still powdery pockets of snow becoming full of lumps and bumps, the remains of previous falls from above thawed then frozen in time.

We were soon back at the steep section which by now was in full sun. “In 45-50 minutes this will avalanche!” said Davide, confidently. We saw another tourer making his way upward: “You just cannot tell some people” Davide said, annoyed.

We inched our way across the slope, gingerly making our way upward. Though it was only just gone 11am the heat of the sun was powerful and I could feel beads of sweat running down inside of my merino wool top, it was also partly nerves.

Once we cleared the slope we settled on a rocky outcrop and ate our lunch. An Italian skier was there chatting to Davide about his climb.

h2
After lunch it was a couple of hundred metres further down back to the hospiz

From here it was just another couple of hundred metres down to the hospiz which loomed in the valley below. Big, sweeping turns were the order of the day, the crusty snow of this morning now very soft and forgiving. At the end of big ski runs you normally have a bit of time to relax but such was the state of the snow I found that I needed to concentrate to make sure I didn’t do the customary splayed herringbone faceplant.

Back in the car park we discovered it was summer, a few people milling around in shorts and T-shirts. A French couple in a campervan saw us and began walking toward us armed with touring maps. Davide, ever the mine of information, was happy to oblige with advice on where to go.

simp car
The car park for the Simplon Pass cafe had huge 18ft drifts that had been previously ploughed

“Shall we go for a beer?” With that we were soon driving to the pass cafe, the kind of place that gets full up with bikers in summer. On this day there were just a couple of tables of people enjoying beers and the customary bratwurst and frites. I marvelled at the wall of snow piled up by the side of the road – it was that time in the year when you can see the depth of each snowfall.

What seemed a deserted mountain pass at dawn was now the busy trunk road; roadtrain trucks from all over Europe crossed back and forth. Davide said it was one of the most intensely maintained roads in the world – being above 2,000m snowploughs are utilised almost 24 hours a day during winter storms.

This was probably my favourite day out of the four. The area has unlimited possibilities and everything feels so close to nature, and so far away from it all. As we finished our beers I asked Davide what he thought of the UK’s current political predicament: “Brexit? What is Brexit?” was his bewildered reply.

matt
Zermatt with the iconic Matterhorn in the distance

Though I’d visited Zermatt a couple of times before they were both flying visits and was keen to return with someone who knew the area inside out. And though my final peak, another mountain call the Breithorn, was by far the highest at 4,164m we were able to get a lift all the way up to the Klein Matterhorn at 3,883m.

Though the lift took a huge amount of leg work out of reaching a peak of the same height there was still much left to do technically to get to the summit. And though the weather was perfect with just a bit of a cross breeze it was still an unforgiving environment; you had to keep your wits at all times, especially when you began to cross part of the glacier that is sheet ice, the result of countless freeze-thaw cycles.

looking up
The huge glacier field on the way to the Breithorn summit

And though the final ascent was under 400m the added altitude made a huge difference on speed of progress, a question of small movements and keeping to a rhythm.

Being more accessible there were far more people around than previous days, most taking advantage of the incredible weather.

We were able to spend longer on the summit this time, being much earlier in the day avalanches are much less of a risk. The view from the crest of the ridge was breathtaking, you could see for miles down into the green valleys below.

summit breit
The summit of the Breithorn with the Matterhorn in the distance

Our descent was rapid, catching the snow at just the right time. We were more than ready for lunch. After four of the hardest days skiing of my life I took my time over lunch on a sunny terrace but it wasn’t long before we were back in our skis. It felt strange to be skiing a piste for the first time after being in the mountains for nearly a week.

I was keen to get a good look around the area and, with empty, end-of-season, pistes we were able to cover a lot, taking in the glacier slopes on the Klein Matterhorn side before moving over to the even quieter Stockhorn/Gornergrat which has a very charming old railway that’s full of tourists.

An experience that I will never forget.

 

 

 

Summer 2018 forecast: average

The thundery end to spring has probably built everyone’s hopes up that we’re about to experience a summer with plenty of fireworks in the atmosphere. But the current pattern that brought four consecutive days of thunder (the whole year average is 3.5!) – a continental influence on our weather – could just as easily flip to a mobile south-westerly.

Screen Shot 2018-05-28 at 10.34.52
Thunderstorms will probably continue to be a feature of the summer

The mean temperature for summer 2018 is looking average overall with average precipitation.

Like the most recent winter forecast I’ve looked in depth at ENSO, QBO and local meteorological data.

ENSO

The El Niño–Southern Oscillation (ENSO) is a periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean. Current neutral conditions are forecast to continue through to September so any impact is likely to be very small. I had a look at similar years were ENSO was 0.2 in May and came up with the following.

Temperature
Average: 40%
Rather cool: 40%
Cool: 20%

Rainfall
Average to slightly dry: 60%
Average to slightly wet: 40%

Sunshine
Average to slightly sunnier than average: 60%
Average to slightly dull: 40%

QBO

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 only two similar years: 1963 and 2010.

Temperature
Average: 50%
Cool: 50%

Rainfall
Average to slightly dry: 50%
Average to slightly wet: 50%

Sunshine
Average to slightly sunnier than average: 50%
Singularities / patterns

sunset

Spring was consistently on the wet side this year with all months at least 127 per cent wetter than average, the total of 182mm made it the wettest for 10 years.

 

The mean temperature for the spring season, despite the very cold start, ended 0.8C warmer than average, just under a degree colder than last spring which was the second warmest on record.

If you take into account all years back to 1797 that were within +/- 10 per cent of these figures, some 10 ‘best fit’ years emerge.
The list of 10 summers, ranging from 1801 through to 2007, predominantly saw summers that were just on the cooler side of average – no real corkers stand out except for 2001 which saw a hot spell at the end of July that made it into my list of best heatwaves.

As an average this summer could be expressed as: Mean: 17.1C (just below average) Rainfall: 150mm (about average). Sunshine 535 hours (just below average)

Or, expressed in probabilities, I concluded the following:

Temperature
Average to slightly below: 50%
Average to slightly above: 20%
Rather cool: 20%
Cool: 10%

Rainfall
Average: 50%
Wet: 30%
Dry: 20%

Sunshine
Average: 10%
Average to slightly sunny: 30%
Average to slightly dull: 40%

 

From the above you could deduce that the next three months will be slightly below average for temperature, with average rainfall. And slightly duller than average.

To try to give some idea of what month will have the best weather I’ve broken down the summer into June, July and August probabilities.

Looking at June, after the weekend, the outlook is looking unsettled and gradually turning cooler after the first week. July looks average as does August which, apart from two years, has been a very disappointing summer month.

Perhaps the best weather this summer will be at the end of June and the second week of July – just as most schools break up?

 

* Taking into account the fact that temperatures in London are up to 0.66C warmer than they were 100 years ago I have added 0.66C to mean temperatures before 1915.

** Obviously, in the event of a series of direct hits from thunderstorms, my rainfall estimate could be hopelessly short – a symptom of abundant solar energy at this time of year which creates a ‘noisy’ atmosphere compared with winter.

*** The 1981-2010 average mean for summer in this region is 17.6C, with 144.9mm of rain and 564 hours of sunshine

Thunderstorm: May 29th 2018

Posts about thunderstorms are usually few and far between – the average number of thunderstorms in this part of the UK in a summer month (July) is just 3.5.

So experiencing four in four days must be very rare; the record for thunderstorms in a month is 12 in June 1982 though I’ve no idea how many of these were on consecutive days.

While the storms over the weekend were all about lightning this one was all about rain and loud thunder. Tuesday, May 29th, started cloudy and dull with some light rain. I was expecting some rain but it lingered and became heavier at 11.30am before turning torrential at 1pm, going against forecasts from BBC and Met Office – the trough was a lot further north than modelled. I pointed this out to the UKMO to be told that a yellow warning was in place for the whole SE region.

29th rain
The bulk of the rain fell between 1pm and 2pm
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A marked drop in pressure coincided with a bright flash of lightning that was almost instantly followed by thunder that was as loud as cannon fire

Some 26.5mm fell in just over two hours bringing lots of surface water and flash floods around Leyton and Walthamstow. At 1pm, while driving in this area, a bright flash was quickly followed by cannon-like thunder. A further fall in the early hours brought the 09-09 total rainfall to 29.8mm, the 5th greatest May fall since 1959.

With the storm the previous evening the 48hr rainfall total was 40mm!

In the neighbouring borough of Barking and Dagenham it was reported that lightning struck a chimney which caused a fire in a terraced house in Rush Green at 2pm.

Local media pick up the story here, here and here.

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The position of the storm around the time of the loudest thunder
South acess
South Access Road in Walthamstow suffered flash flooding as drains failed to cope with the volume of rainfall
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The trough on this FAX chart suggested the heaviest rain would be slightly further south than it was

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The Met Office forecast for Tuesday shows how useless auto generated apps can be, the 10-20% risk of rain between 1300-1400 contradicts the yellow warning
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Posted by Simon Cardy: “The large mature Cumulonimbus clouds over SE England (outlined purple on the map) are producing frequent lightning, very loud thunder and heavy rain. (credit: EUMETSAT).”