The latest offering from the GFS model predicts a rather cold northwesterly airstream on Christmas Day, a bright looking day with wintry shower especially across northwestern areas. This brief cold snap may well be the last in a series of cold north or northwesterly incursions that you can trace back to the end of October (fig 1).
As so often happens between Christmas and New Year, the weather drastically changes in mood, and this year doesn’t fail to disappoint in this regard, as it turns progressively milder on Boxing Day, and by the start of 2018 its super mild across the British Isles and the bulk of Europe, if this chart for January 1st is to be believed (fig 2).
The GFS solution does contradict the latest extended outlook from the Met Office though, which suggests that in the final days of December “Temperatures will be near to or below average and snow is likely, at times”, they go on to imply that things might turn more settled and anticyclonic as we go into January 2018 (fig 3). As always, it will be interesting to see what transpires in a couple of weeks time.
If I’ve got my programming right, the latest 12 month precipitation accumulations at the end of November for the UK, are still on the low side for Central, Southwestern and Southeastern parts of England (fig 1). The daily precipitation data is from the UKP gridded set which I download from the Met Office. The lowest anomalies at the moment are across the Southeast with 85.9% of the 1981-2010 long-term average (fig 2). After a wet spell in mid-summer accumulations were creeping back close to average, but it looks like a dryish October and November has put them back into a deficit.
The index of reservoir totals for England and Wales looks close to normal (fig 3), despite a number of reservoirs in the south being on the low side.
The Climate Prediction Center issued a La Niña Advisory on the 14th of December 2017. It said that a La Niña event is likely (exceeding ~80%) through the Northern Hemisphere during the winter of 2017-18, with a transition to ENSO-neutral most likely during the mid-to-late spring.
I personally find the whole ENSO alert system a little confusing, because if you look at the latest evidence, the SST conditions are still ENSO neutral, and it will require four further months of SST anomalies of -0.5°C or less before a La Niña event can be declared – which means February 2018 at the earliest. This page on the climate.gov website does clarify things.
Saying when an El Niño or its cold counterpart a La Niña event has commenced is rather a complicated business. In my ENSO application I stick by the American rules, which are 5 consecutive months with a SST anomaly of +/- 0.5°C in the Niño 3.4 region. Things are further complicated because these monthly SST are in fact a composite of a centred three-month rolling average. Not only that, even if these conditions are met, if there is insufficient evidence that a strong Walker circulation isn’t present, then an El Niño or a La Niña event is still not in progress (fig 2).
That’s why my application is showing a La Niña event happening during the last five months of 2016 (fig 1), although the values indicate that a short-lived La Niña was in progress, the Walker circulation was probably weak. As the Wikipedia article points out most countries around the rim of the Pacific ocean have a different way of declaring an event is in progress:
“Currently, each country has a different threshold for what constitutes an El Niño event, which is tailored to their specific interests. For example, the Australian Bureau of Meteorology looks at the trade winds, SOI, weather models and sea surface temperatures in the Nino 3 and 3.4 regions, before declaring an El Niño. The United States Climate Prediction Center (CPC) and the International Research Institute for Climate and Society (IRI) looks at the sea surface temperatures in the Nino 3.4 region, the tropical Pacific atmosphere and forecasts that NOAA’s Oceanic Niño Index will equal or exceed +0.5 °C for several seasons in a row. However, the Japan Meteorological Agency declares that an El Niño event has started when the average 5 month sea surface temperature deviation for the NINO.3 region, is over 0.5 °C (0.90 °F) warmer for 6 consecutive months or longer. The Peruvian government declares that a coastal El Nino is under way, if the sea surface temperatures in the Nino 1 and 2 regions, equal or exceed +0.4 °C for at least 3 months”
You might be thinking it’s been quite a snowy end to 2017 wherever you live in the country, but spare a thought for those of us down here in the southwest who so far have yet to see a snowflake. In Cornwall none of the SYNOP stations have reported an air frost so far this Autumn, and even here in mid-Devon although we have had four air frosts, and only one of these was for a temperature lower than -0.2°C.
I’d like to do a similar thing with snow that I do with frost, by checking for the occurrences of snow in the present weather from the hourly SYNOP files. Not only would that mean opening thousands of hourly SYNOP files, but many of the AWS reports either don’t report a present weather, or if they do they’re not that reliable when it comes to the reporting of freezing precipitation. The same thing applies to the reporting of thunderstorms, I have yet to see an AWS report a thunderstorm, even though I know the more sophisticated Vaisala systems are capable of sensing them.
I have a few ‘meteorological’ heroes in my life, and it may come as a surprise to many that Peter Ewins or Julian Hunt don’t feature in the list. At the top of it must come Gordon Manley (1902-1980), whose name I first came across when reading his 1952 book ‘Climate and the British scene’ as a teenager. He is best known for his work on reconstructing the past climate of Central England with his CET series, which was adopted and sanitized by the Met Office, which I noticed that he joined in 1925, but had the good sense to resign the very next year!
Along side Manley at the top of my list of meteorological heroes is Hubert Lamb (1913-1987). It was Lamb who catalogued the circulation patterns across the British Isles from 1861 and came up with the idea of ‘Lamb’ weather types, which as far as I know extended the earlier work on weather types done by Van Bebber and Gold. That work has been carried forward by the CRU at the UEA, although they switched to an objective rather than Lamb’s original subjective way of classifying each days weather type. In 1964 he was asked to write a new edition of a book called the ‘English Climate’, another very readable book that I first came across when I joined the Met Office. Lamb did work on and off for many years with the Met Office, in fact from before the war until 1971. The second world war was a problem for him because as a Quaker he couldn’t directly get involved in it. The answer was that he work in the Republic of Ireland for the duration of the war with Met Éireann. He finally saw the light late in his career, and had the good sense to leave the Met Office for academia and launch the CRU at the UEA.
Looking at both of my heroes, I can see the connection between the two is that they were both instrumental in creating important climate data series with the CET and LWT. For some reason that appealed to me, and as soon as I had invested in a BBC micro in 1982, it was the first thing that I felt impelled to write a program for – the rest as they say is history!
The connection between these two esteemed gents and myself, apart from our innate love of the climate and weather of the British Isles and resigning from the Met Office, is a fondness for its hills and mountains.
So when I came across an interview with Hubert Lamb recently on the WMO website I just had to include some of the more interesting questions that he was asked. It was in a publication called the Bulletin Interviews and here are a few of the questions that he was asked that I found interesting. As far as I can see the interview took place before 1981.
Hands up how many of us have a love of weather that started when we experienced a snowy winter as a child?
I never realised that Richardson was also a Quaker, he too would also feature in my list of meteorological heroes.
This story of Lamb’s reminds me of the thick smoke haze that we would get in the Vale of York when I started my observing career at RAF Leeming in 1970. I can still remember reporting 800 metres in smoke behind a light northeasterly sea breeze that was blowing down from Middlesbrough. Thankfully things are a little cleaner these days.
It’s a shame that the Met Office don’t share Lamb’s passion for past climate data, they’ve recently left the digitising of the DWR records to the Weather Rescue volunteers. What would Lamb have thought? No wonder he left.
I like the bit where he says about climate warning – “…there is also the dangerous tendency to think that Man is responsible for all occurrences. That should be viewed with considerable scepticism“.
Unfortunately the ‘Bulletin interviews’ doesn’t feature an interview with Gordon Manley which is a shame.
Temperatures fell to -13.0°C overnight at Shawbury (fig 1). Not a real surprise, because it’s a well-known fact that Shawbury plus a clear night and light winds, plus a snow cover equals a very low temperature. It still holds the record for being the coldest place in England, when almost 36 years ago now, the temperature fell to -25.2°C on the 13th of December 1981, when there was a similar depth of snow on the ground. As far as I can see this table of top ten coldest places in the UK from the Met Office blog is still correct (fig 2).
Having said all that last night was not a perfect radiation night at Shawbury as you can see from the observations (fig 3).
The wind never really dropped out, although this didn’t prevent them going into fog at 23 UTC, when the temperature suddenly dropped from -3.0°C to -9.2°C. Fog or freezing fog, as it may well have been, will slow or even halt the fall in temperature depending on its thickness, and if these observations are correct the minimum may have occurred around 05 UTC, because the next hour it rapidly warmed from -12.4°C to -6.9°C, before falling again (fig 3).
Looking back almost 36 years, here’s the 00 UTC chart for the 13th of December 1981 (fig 4). As you can see the minimum at Shawbury that night probably occurred close to midnight. It’s interesting to speculate that if the ridge of high pressure had just hung on for another 6 hours instead of collapsing like it did, the minimum temperature at dawn may have matched the -27.2°C extreme minima recorded in Scotland.
Just a week ago the Met Office were saying in their extended outlook that the weather looked blocked into the New Year, just a week later they’ve changed their mind – well these are the days of climate change – it looks likely that the current regime of blocking and occasional northerly outbreaks of the last few weeks, will give way to a spell of more zonal, milder and windier weather before Christmas, although they do say that the New Year could see things turning quieter and more settled (fig 1).
The bullet list below is a quick look at the LWT for 12 UTC each day from the latest GFS model run, and things do seem to be turning milder and progressively more cyclonic well before Christmas.
12 Dec – W
13 Dec – W
14 Dec – CW
15 Dec – NW (last of the cold northerly outbreaks)