Category Archives: UK climatology

Where’s east London’s rain coming from?

April 2019 was yet another dry month. Just under 12mm was recorded, that’s 28 per cent of average.

There has been rain around but the prevailing wind has not been conducive for great amounts to fall here. Last weekend, over a period of 5 days, just 0.9mm fall. Yet Capel Curig in Snowdonia, 200 miles northwest as the crow flies, recorded 130mm thanks to a NW’ly regime.

A look at rainfall in Wanstead back to July 2013 shows that of the 3,550mm recorded just 17 per cent has fallen when the wind was NW’ly.

Because of the topography of the area most of our rain falls when the wind is blowing between SE’ly and SW’ly, a total of 43 per cent.

A westerly is usually reliable for rainfall, however because this area is in the lee of high ground areas such as Hampstead westerlies have delivered just under 8 per cent of that 6-year total.

rain rose

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Is it warm, cold or just normal?

Saying how warm or cold a day feels is subjective; one person’s hot day in spring is another’s ‘on the warm side’. Similarly when someone says the temperature on any given day is ‘normal for the time of year’ others will be exclaiming how cold they’re feeling.

The ‘heatwave’ in February was a case in point. Though many places recorded their warmest February maxima on record many were saying it was just a nice, warmer than normal spell of weather.

Some years ago the Met Office issued guidance on how warm or cold a day was relative to the anomaly. Earlier this month the table was posted on Twitter and I have plotted a graph for the spring period.

Today’s (March 22nd) maximum of 11.1C is therefore described as ‘normal’.

temp feel

cold hot warm

 

Data reveal windiest March for 4 years

March 2019 has been a windy month so far. With 11 days to go it is already the windiest March for 4 years and the windiest month for over a year.

The windiest month recorded since 2013 was December 2015.

Looking at the data in general there seems to be a pattern of a windy month that is followed by a decline of between 10 and 13 months.

monthly wind run

 

Spring or still winter? Plants reveal all.

With the record warm spell last month and high sunshine totals you would think that the growing season is well under way. Spring bulbs have been out for weeks, trees are blossoming and many shrubs are on the verge of flushing.

But a look at the local temperature records over the last six years shows that things aren’t as advanced as previous seasons.

Considering the period from December 1st – in recent years a date when it is common to see bulb shoots beginning to emerge – to March 10th reveals the following table in terms of growing degree days.

growing degree days

The warm days of last month were cancelled out by cold, frosty nights, leading to little net warmth. And the last ‘growing degree-day’ was on March 2nd. Nevertheless growth is further on than last year that saw record cold in March. 

The season is a long way behind 2015-16, however, which saw a record-breaking mild December.

Looking at the list below, and the at best average outlook, we’ve still got a way to go before we’ll see most trees in full leaf…

plant development
This list courtesy of Wikipedia

 

 

Winter 2018/19: average with extremes

The winter of 2018/19 will probably be remembered most for the remarkable warmth in the last week of February. And for its lack of snowfall.

The mean temperature finished 6.1C, that’s 0.7C above average, the mildest for 3 years.

Rainfall was below average: 127mm fell, that’s 87 per cent of average and the driest for two years.

Sunshine was well above average: 211.6 hrs is 126 per cent over average, the sunniest for seven years.

The warmest day of the winter occurred on December 30th with 14.2C recorded. The warmest night was on January 28th when the temperature fell to just 10.8C.
The wettest day of the winter occurred on January 2nd when 15.3mm was recorded.

Snow first fell on 5 days between January 22 and February 1st: five days of snow falling and two days of snow lying over the three months is below average.

There were 29 air frosts during the three months, seven above the 1981-2010 average.

A full weather diary is available for the months of DecemberJanuary and February. To view full stats for each month follow this link:http://1drv.ms/1kiTuzv

TMax winter

Summary for period 01/12/2018 to 28/02/2019

Temperature (°C):
Mean (min+max)   6.1
Mean Minimum     2.6
Mean Maximum     9.7
Minimum          -6.5 on 30/01/2019
Maximum          18.7 on 26/02/2019
Highest Minimum  11.5 on 06/12/2018
Lowest Maximum   1.3 on 23/01/2019
Air frosts       29
Rainfall (mm):
Total for period 127.0
Wettest day      11.4 on 20/12/2018
High rain rate   28.1 day 26/01/2019
Rain days        31
Dry days         59
Wind (mph):
Highest Gust     31.1 on 09/02/2019
Average Speed    2.8
Wind Run         6152.3 miles
Gale days        0
Pressure (mb):
Maximum          1043.8 on 02/01/2019
Minimum          980.4 on 01/12/2018
Days with snow falling         5
Days with snow lying at 0900   2
Total hours of sunshine        0.0

Ben Nevis: a serious mountain

Strong winds, hail, sleet and snow were experienced in abundance when I climbed the UK’s highest mountain at the weekend. ben start

To give us a chance of making it to the 1,345m summit and back we left Fort William in darkness. Heavy rain that had greeted our arrival the previous day had abated but the spooky balminess of this early January remained; a local thermometer was reading 11C at 7am!

A gorgeous purple hue tinged the early morning dawn as we began our ascent though it was not long before the rain returned.

 

Proceeding upwards, after about an hour, we passed another climber who was walking down, having abandoned his attempt because of ‘atrocious conditions’. “I’m more of an ice and snow climber,” he explained, telling us how wonderful conditions had been in Zakopane, Poland, just a few days previous.

Unperturbed we pushed on soon making it to the tarn – the Lochan Meall an t’Suiche. We had ideas to climb the Ben via the Carn Mor Dearg arête but a wrong turn and conscious that time was not on our side we turned back and continued on the pony track / tourist route. Just over two hours in we passed the ford, just below which the route begins zig-zagging its way up to the summit.ben tarn

By now the rain started to get heavier. At around 900m it turned to hail. It was at this point that we passed another climber: “It’s snowing on the summit but you don’t need crampons,” he exclaimed before hurrying on down. We passed a further dozen or so walkers on our way to the summit; all of them looked like they couldn’t wait to get off the mountain. The rain was now a wintry mix of hail, sleet, snow and frozen rain – painful to walk into in the strengthening wind.

ben paul bothyAs the peak started to level out around 1,150m snow was now beginning to settle on the rime that had built up on the cairns; we’d got what we’d come for! It was here, however, that I realised my waterproof trousers weren’t so waterproof. First dampness then rivulets of water began flowing into my boots.

The peak was now well fogged in and for the first time I felt a bit uneasy, conscious of the fact that the wind was also still gathering strength. Regardless, my climbing pal continued to press on just ahead of me. Poor visibility concealed the summit which was still another 100m or so higher. Although he’d previously climbed the Ben (in perfect summer conditions) he’d forgotten exactly where the trig point was and was careful to observe the cornices to the side, so lethal to inexperienced walkers who fall through them every season.

We made a beeline for the bothy close to the trig point; my climbing partner, who was also trying to deal with waterlogged boots, was keen to change socks. At that point a gust of wind caught the bothy door – it smashed open leading to the rime that had built up on the hut to fall to the ground. I was starting to feel well out of my comfort zone and I persuaded him against the sock change, saying we needed to turn around and get down as quickly as possible. Despite both having crampons in our rucksacks I decided against spending more precious time trying to wrestle them on to our boots. Although the ground was coated in rime I knew that the warm front that was coming in was already lifting the temperature – and we’d cope without them.

ben paul trig

The route down was easier if unpleasant. Once we’d descended far enough out of the cloud and wind I knew we’d be OK and it was just a case of taking it steady over the uneven cobbles.

Night was fast drawing in by the time we arrived back at the Ben Nevis Visitor Centre. As we called a cab for the short drive back to Fort William all I could think about was a hot bath back at the hotel and a welcome pint by the fireside.

All around Fort William it is frequently mentioned that conditions at the top are totally different and that the Ben should not be under-estimated. As someone with nearly four decades of experience of being in and around mountains I should know better than most. But Ben Nevis is not just any mountain and deserves complete respect.

The meteorology of the climb

aonach
The temperature trace shows that the warm front arrived after 11am
aonach wind
The WSW wind was gusting F6/F7 giving a windchill of -5C and lower

* Despite the awful conditions I did manage to get a few photos, including the observatory where Victorian scientists lived for 20 years, gathering meteorological observations until 1904. Experiencing just a taste of the conditions that they would have had to endure makes their achievement all the more remarkable.
The observations have recently been fully collated and are providing valuable insight into the study of how mountain conditions have changed since that time.

** The following article was printed in the Lochaber News, 9th January, 2013

Stupidity can get you killed

The leader of Lochaber Mountain Rescue Team has issued a strongly-worded warning in the wake of a walker’s “act of sheer stupidity” in trying to tackle Ben Nevis in winter in trainers.

John Stevenson (58), who heads up Britain’s busiest mountain rescue unit, said a man rescued on Monday afternoon was fortunate to be alive after attempting the country’s highest peak without proper equipment for the conditions and time of year.

The 31-year-old walker was airlifted to hospital in Fort William after he fell while descending the 4,409ft, snow-covered Ben. He sustained a leg injury while walking on the main mountain track and managed to alert the police to his situation at about 4pm.

A full search and rescue operation was launched involving police, 18 mountain rescuers and a Royal Navy helicopter from HMS Gannet, Prestwick.

The injured man was located and airlifted from the Red Burn area, above Lochan Meall an t-Suidhe, and was treated at Belford Hospital for his injury and the effects of the cold.

Mr Stevenson said the incident could have turned to tragedy.

He said: “He’s an extremely lucky young man to have survived.”

“His equipment was just rubbish – he had nothing. He was wearing trainers and didn’t have a torch.”

“He did everything we tell people not to do. When we found him he’d lost one trainer, the backside was out of his trousers and he was wet and cold.”

“There’s no doubt in my mind that he would not have survived the night if he hadn’t phoned in on his mobile, and we were lucky enough to find him.”

“He didn’t actually set off on his ascent until 11am, having come straight off the train at Fort William. That’s just a ridiculous time to be starting out when darkness falls at about 4pm. It’s crazy and not on at all.”

“He made it to the summit okay but slipped on the way back down and managed to call the police on his mobile phone.”

Mr Stevenson added: “Initially he was on the so-called tourist path but he lost his way and veered off the path.”

“He slipped and hurt his leg but kept on walking – but realised he was lost and phoned the police.”

“He was talking to the police as he walked and then the phone just went dead. All the officer could hear was running water.”

“We had been alerted by this time and were on standby, so when the line cut out we all feared the worst.”

“I knew the only place on the top half where you can hear water running like that is the Red Burn, so we sent two members of the team up with the helicopter, as well as members on foot. Luckily the first two found the casualty pretty quickly. He had fallen but was okay. He’d lost his phone.”

Mr Stevenson said he found it increasingly frustrating that, despite annual messages from rescue teams, climbing organisations and the police, walkers were still heading to the mountains ill-equipped for the conditions.

“People need to be prepared,” he urged. “They need to heed the advice about having proper equipment and clothing.”

“The thing is, so many people get away with it every year, but unfortunately many don’t and end up injured – or worse.”

“The man on Monday was very lucky indeed and we could see he was extremely relieved to be off that mountain.”

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November 2018: average and rather sunny

November was most notable for the amount of sunshine. Some 79 hours were recorded, that’s 135 per cent of average, the sunniest November for two years.

The mean temperature finished 8.4C, 0.4C above average, the mildest November for three years.

Some 72.5mm of rainfall was recorded, 122 per cent of the 1981-2010 average, the wettest November for two years.

To view full stats follow this link:http://1drv.ms/1kiTuzv

november 2018

London winter forecast 2018-19

Long range modelled forecasts have been all over the place of late and, looking at the underlying signals, it is easy to see why.

When I’ve produced these forecast in the past, in terms of QBO and ENSO data, there’s usually a lot of analogues to compare with. This year, however, seems to be an exception.

Considering QBO first I looked back over data to 1950 and found nothing similar for October. However, looking over the whole series the cyclical nature of this circulation may give some clue.

bestfit

Some 20 months were revealed, ranging from June 1959 to June 2015.  Using NOAA’s  Niño 3.4 region I narrowed this list down to the few that had an ENSO value of around +1 with a rising trend. With NOAA’s forecast of a Modoki El Nino (one that occurs in the central Pacific) this narrowed the list to just 1 period: June 2015. Considering maxima anomalies this would give the following winter.

winter 2018-19 max anomaly.PNG

The above would suggest there being a general cool down through December with a cold spell starting just before Christmas into the new year? And another cold spell end of January into the first week of February?

winter 2018-19 precip anomaly

The above precipitation anomaly chart would suggest a wetter than average December,  January and February, though February by much less so.

It’s been a very busy autumn so I’m keeping this short.

The below figures, particularly January and February, may be different in the event of an SSW occurring. In all then.

The mean:
December: +0.8C
January: -1.2C
February: -1.7C
Overall: -0.3C (broadly average)

Precipitation:
December: 158%
January: 155%
February: 120%
Overall: 134%

 

How cold will November end?

Twitter and other forums have been at fever pitch with excitement for a ‘nailed-on’ cold spell. 

But with many getting carried away over tales of a repeat of March’s ‘Beast from the East’ it is important to remember that snow in November is extremely rare in the south-east; despite predictions of the incoming upper air being very cold the ground is still very warm and will take time to cool.

However, as seen in November 1993, a week of hard frosts were enough to chill the ground enough for a decent week-long cold spell. Similarly, although the snow didn’t arrive in London until December, November 2010 was also cold enough.

The weather of late has been in an ‘average mood’ with the mean temperature in September and October both finishing at 0.2C below. The mean for the this month is currently (on the 15th) running 1.8C above average, therefore for the mean to finish the same as September / October would require a big cool down, as hinted by the models.

Will we see another an average, 1993 or a 2010 end to the month. My hunch is it will be something between the three.

Below is a graph that shows this November so far with average, 1993 and 2010 ends.
2018: 0.4
1993: -0.8
2010: -1.4

East London’s highs and lows of the last 60 years

The chart below shows every maximum and minimum temperature recorded in this area since January 1st 1959, some 21,860 days!

The extremes range from -12.7C recorded on January 31st 1972 to 37.5C on August 10th 2003.

After peaking in 2003, summer maxima seems to be in decline. Winter minima, by comparison, has been increasing since 2012

maxmin