No ice day for London

There was much talk yesterday about a lot of the south of the England recording an ‘ice day’. screen-shot-2017-01-27-at-12-31-17

In the London area most places missed out because the temperature rose briefly above freezing around dusk and also just before the 0900 observation today.

So although it felt brass monkeys out there it doesn’t count.

Ice days are when the temperature fails to rise above -0.1C over a 24 hour period, usually from 0900 to 0900. The confusion over yesterday’s ice day was caused by the fact that some stations release a 06-18 maximum reading – both Kenley and Shoebury stayed below zero in this time period.

Ice days in the Wanstead area are probably even rarer than decent snowfalls. Since 1959 there have been 81 ice days.
The last time the temperature failed to rise above 0.0C was January 20th 2013. The last time the temperature failed to rise above -0.1C (a true ice day) was January 6th 2010.

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Over a dozen stations stayed below freezing for 24hrs to 09z on January 27th

Stephen Davenport’s synoptic analysis of the event is included below:

“[The cold conditions were] all thanks to this nicely (or not nicely, depending on your view) blocked situation. On Tuesday 24th a 500 hPa ridge started build northeastwards to the north of  a small upper low situated over France. By 12z on Wednesday 25th it had cut off to leave a classic-looking Rex block over western Europe:

Surface winds from the Continent started to bring colder air across as the temperature anomaly analysis for 12z Wed 25th shows, while milder southerlies continued across Ireland and Scotland, and brushed western Wales and SW England:

By 12z Thursday 26th the block was becoming more omega-like…

… and cold air continued to percolate north-westwards from the Continent farther across the British Isles:

There’s a certain beauty in the sinusoidal flow around a Rex block, I always think.”

 

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December 2016: driest for over 80 years

December 2016 was the driest 12th month in over 80 years and the 5th driest in a record going back to 1797.

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Christmas day was the second warmest on record in London

The total fall of 8.3mm is just 16 per cent of what normally falls in December, marginally more than December 1933. The mean temperature of 6.1C was 0.5C above average, though 4C colder than the record December last year.

There were 51hrs of sunshine, that’s 125 per cent of average.

The wettest day was on the 10th when 5.2mm of rain fell. The warmest day occurred on the 9th with 14.2C recorded. The lowest temperature occurred on the 28th when the spirit fell to -4C.

The sunniest days were on the 4th and 29th when seven hours of sunshine were recorded.

Air frosts: 8, Ground frosts: 14

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Fog, frost and black ice all featured during December

Though January has started on the chilly side in the short term the weather will turn mild. Beyond that there is a suggestion that the weather could turn on the colder side of average with some models suggesting a cold snap with snow around mid-month.

My usual method of prediction to the end of the month has been scotched by the very dry December. The only years that were similar were both far colder than last month – the usual pattern of a dry month being cold or very cold was broken.

With the unprecedented warmth at the North Pole, last year’s odd behaviour of the QBO and a weak polar vortex we are in unprecedented territory in terms of what could happen later in January. My hunch, though, suggests the month will end up average to rather cold with little precipitation. Any cold spell with probably be the short-lived variety with a couple of inches of snow that lasts three days.

So, to sum up, we’re looking at a mean of 4.4C, rainfall: 55mm, sunshine: 39hrs.

In view of the above my forecast last month was very poor: predicted mean 4.4C (result 6.1C). Rainfall: 55mm (result 8mm). Sunshine: 39hrs (result 51hrs)

I have also published a winter forecast covering the London area that you can find here.

Here follows the full weather diary for December…Full stats for the month here:http://1drv.ms/1rSfT7Y

1st: Sunny start though the frost lifted readily into low cloud and mist to leave a chilly afternoon.
2nd: Cloudy, quiet and cool weather all day.
3rd: Cloudy and quiet all day. Feeling cold.
4th: Sunny , frosty start. Quickly warming up to leave sunny, cloudless afternoon.
5th: Sunny start, then patchy cloud – this thickening before becoming foggy overnight.
6th: Misty start after fog overnight. Cloudy most of the day though there was a brief clearance around midday.
7th: Cloudy most of the day though there was occasional brightness.
8th: Dull day though with a little limited brightness early afternoon.
9th: Cloudy but wth more brightness than yesterday. Very mild. Cloud thickened with light rain around 11am. This gradually grew heavier as the day progressed and was moderate overnight.
10th: Bright start and feeling mild, then cloudier and damp.
11th: Cloudy and dull all day.
12th: Dull all day with light rain early and late. Clearer spells overnight but overcast again by dawn.
13th: Dull with bits and pieces of drizzle up to 11.20am.
14th: Bright start with lots of cirrus and altocumulus – this gradually cleared to leave a warm and pleasant afternoon.
15th: Dull and cloudy with limited brightness.
16th: Dull and cloudy start.
17th: Foggy and dull all day.
18th: Misty start with fog above 90m on cycle ride. Then dull and grey all day. Mild.
19th: Dull and cloudy all day – some spots of drizzle.
2oth: Sunny start but clouded over late morning. Cloudy thereafter with some drizzle overnight.
21st: Cloudy start then sunny. Cloud returned and turned dull and dreary in the afternoon with odd drizzle.
22nd: Bright, misty start
23rd: Cloudy start with breeze beginning to build as a result of Storm Barbera.
24th: Cloudy and dull all day. Very mild. Temp increasing overnight with approach of warm front .
25th: Cloudy, breezy start. Remained dull all day though brightness was seen over the Thames and North Downs, disrupting the SW’ly flow.
26th: Sunny, hazy start and turning colder.
27th: Sunny, frosty start, the air pressure record of 2012 has been broken.
28th: Foggy start, the fog persisting to late morning before sun broke through leaving a chilly afternoon. Frost returned quickly after dark, a clear night.
29th: Sunny and very cold and frosty start. Frost returning after dark with fog forming in the early hours.
30th: Foggy and dull all day, the fog thickening up at nightfall. Approaching cloud lifted the fog and temperature.
31st: Dull and overcast to start – this sticking around all day.

30 years on: the January 1987 cold spell

I remember the January 1987 spell like it was yesterday. I’d arranged to stay with my aunt and uncle in a rural part of south Essex. The forecast by Ian McCaskill on the Friday night was for a cold weekend with possible snow flurries near the coast. ‘That’ll do’, I thought.

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The upper air on 13th January 1987 was extremely cold. I don’t think it has been as cold since

I caught a mid-morning train from Romford on the Saturday morning. As I disembarked at Rayleigh I was shocked by how cold it seemed to have turned. The wait at the bus stop was made worse as my uncle was delayed in picking me up; a black leather jacket I was wearing at the time was totally inadequate.

No matter, though, as I was soon warmed up on reaching my aunt’s house, helped further by hearty home cooking. Saturday was spent driving round rural Essex: my uncle knew a few farmers and was a keen rambler. We walked a circuit around Hanningfield reservoir.

I think we watched Back to the Future that night. By the time I went to bed I remember there was a dusting of snow on the ground. For some reason I kept waking up, each time looking outside to see the build-up of snow.

snipThere was around four inches by morning and, after breakfast, I went with my uncle for a drive around the same rural spots as Saturday. The reservoir was beginning to ice over and I remember my uncle reading a Fahrenheit thermometer and saying that it was “seven degrees of frost”.

When I left Rayleigh that evening the snow was falling thick and fast and the train seemed to be travelling slower than usual. When it failed to move from Shenfield station after 10 minutes I knew something was up; the guard announced that the wheels had frozen to the tracks. Everyone disembarked and caught another. After leaving Shenfield I noticed that the snow cover gradually decreased, with just an icing-sugar like covering in Romford.

My dismay at having left a winter wonderland in Rayleigh disappeared on waking up on the Monday morning and seeing a good few inches had fallen.

BBC Breakfast presenters gravely told us how bad things were. The Isle of Sheppey was cut off and train services were severely affected – I didn’t go to school once that week because the toilets were frozen. For once the conditions, reflected in this footage from Thames News, matched the hype.

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Courtesy of the Met Office

Many people, including members of the Climatological Oberservers Link, also have vivid memories of the freeze.

East London: Ben Bacarisse was living in Mile End in 1987. He said:  “I was living on the 15th floor of a tower block at the time. The prolonged cold caused the main water riser into the block to freeze so no one in nearly 400 flats (there were a pair of blocks) had running
water.  It turned out to be possible to tap into the larger street main
with a stand-pipe. screen-shot-2017-01-08-at-13-35-00

Presumably the constant use kept it running though
I’d have thought it would have to be removed at night.  I don’t recall
how long that lasted but it was more than a couple of days.”

Home Counties: George Booth, who was living in Epping, Essex, at the time, explained how the weather affected him: “On the Monday (12/1/87) I accompanied a group of young scholars to the Science Museum. Despite the cold and snow they were happy to walk to the station (and they behaved themselves). It was a strange sight to see
Exhibition Road covered in that thick brownish frozen dust which occurs
when temperatures are presumably too low for treatment to be effective.
Not so good news for the school roof, however. It eventually had to be
replaced after a water tank/pipe burst after a thaw.”

warblertsGeorge, who ran a weather station in Epping, added: “On 12/1/87 the maximum temperature in Epping was -8.0c and the minimum was -10.0C. The ‘snow depth gradient’ was very steep NW-SE with SE Essex/E London and N Kent receiving much greater falls than places like Epping. However, it was the severe frost that caused many
problems, particularly in older buildings.”

Dave Cornwell, a retired scientist, from Laindon, Essex, said: “I was working as an operational scientist at a sewage treatment plant in Rainham , Essex. (London Borough of Havering, (just east of London). I remember it well because for the first time anyone could remember the sewage was freezing on entering the works through the screening bars, bearing in mind that sewage is flowing underground and starting off quite warm, usually in winter arriving at about 10-12C.

gavs“It was a major engineering problem because the heat was being conducted away by the metal bars and ice building up and blocking the flow. This could potentially have caused backing up of millions of gallons of raw sewage. A smart engineer made some improvised electrical heaters to fit on the bars and we hired massive tarpaulins to put on the north side to try and cut down the wind chill. It worked a bit till the weather turned. I remember taking the temperature at 9.30 am and seem to recall it was  -9.0C.”

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The record cold spell also saw Steve ‘Silk’ Hurley’s Jack Your Body enter the charts at Number 2, a track that more or less launched the UK dance music scene

John Hall, from Cranleigh, Surrey, said: “We had a little snow on the Monday, I think it was, but it didn’t amount to much. We had to wait for overnight Tuesday/Wednesday for serious snow, but then it certainly made up for lost time. On
Wednesday morning, the gritters  must have done a remarkable job on the
roads, as traffic was moving – if slowly – on the B road that runs
through Cranleigh, and I was able to make the 8-mile journey to
Guildford Station.

“But at the station, a railwayman was standing by the entrance
telling everyone: ‘There are no trains. We don’t know when there will be
any trains. We advise you to go home.’ I managed to get a bus back to
Cranleigh, by which time the snow had just about stopped.

“I didn’t measure the depth of the snow, but my subjective impression that Wednesday morning was that it was almost a foot (30 cm) deep.  The wind wasn’t strong enough to cause too much drifting that day, but the following day it became pretty strong, and there was considerable drifting of the powdery snow, with some susceptible local roads becoming blocked. In this southern lowland region I can’t remember another such instance of this ‘delayed drifting’.”
Tudor Hughes, had the added altitude (165m) of Warlingham, Surrey, that made the cold spell even more memorable. “It was just about the most outstanding weather event for me. The 12th was a sunny day with a light NE’ly and a few inches of lying snow and the temperature just wouldn’t rise.
“After a min of -12°C it got up to -9.2°C (12-hr max) which I think is a COL record though obviously not a UK one.  The 24-hr max was -8.9°C, agreeing with the reading from Coulsdon (Ian Currie).
“In the evening some smoky-looking stratus appeared and snow fell from cloud so thin that the moon was visible.  It snowed intermittently for a further 2 days until the level depth was 39 cm.  At the top of the North Downs (Tatsfield) the depth was about 3 times that.”
Tudor added: “The temperature was below -5°C for about 40 hours and below 0°C for eleven days.  I whacked up the heating and opened the loft door.  A burst pipe and frozen tank is the last thing you want.
“The extraordinary thing about January 12th was the lapse rate.  This was no cold inversion – the higher you were the colder it was.  I reckon the maximum at the top of the Downs (877 ft) was -10°C.  There was some relatively warmer air above 700 mb but even so the 1000-500 mb thickness was 498 dam.  Not quite the purple line but well inside the brown one.”
Unlike some cold spells the severe weather was not restricted to the SE corner of England.

The South West: Len Wood, from Wembury, southwest Devon, said: “Even here on the coast this was the coldest spell I experienced since moving here in 1983. We had four successive ice days and my record min of -10.1C was recorded which still stands.

“With quite a biting easterly wind it was hard to keep our bungalow warm.
Cold was coming up through the floors so I blocked the air bricks and we covered the floors with anything we had handy, old carpet, blankets…

“I remember another effect of the extreme cold was to make all the leaves turn black on the privet hedge down the length of our garden. They subsequently fell off. The hedge did recover the next summer though.”

There is a study of the heavy coastal snowfall of January 11-13 by W.S.Pike here.

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Some more charts from Smartie on the Google Group Weather and Climate…

2m temperature and snow depth at 12 UTC 12 January 1987 from a downscaled simulation of 10-13 Jan 1987. The ERA Interim reanalysis was used as initial and boundary conditions. Contours of physical snow depth start at 2.5 cm every 2.5cm.

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The main convergence zones appear quite well resolved at DX ~12km

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This is the first downscaling grid. It has the latest ‘scale-aware’ convection scheme from WRF (Multi-scale Kain-Fritsch). The deep and shallow components should both be active (haven’t confirmed this).

Hourly output from this is used to initialise nested 6 and 2km grids. On the 6km grid the deep convection should be almost off and shallow convection still active.chart-4

On the 2km grid there is no Cu scheme ie. it’s ‘convection permitting’ in the jargon.

The plots can be compared with the letter by Lumb (Weather, 1988,, V43, 31).

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