This thread is for all comments, discussion and analysis of temperatures in the UK during January, with particular emphasis on the Central England Temperature (CET), for the simple reason that it is the longest running temperature series in the world with over 360 years of data. But you can comment on any interesting temperature statistics or data from across the UK, including your own back yard.
This month the big question is will we see an impact in the UK from the Sudden Stratospheric Warming? If we do it may not arrive until mid month. So it could be a month of two halves temperature wise. That said it looks like high pressure may dominate the early part of the month which could also bring cold conditions to some. The closing days of December are seeing high pressure but a cloudy high with winds from the SW or W so relatively mild. Predicting temperatures in the winter under high pressure can be very challenging as the position of the high and the amount of cloud that gets trapped in it is critical. Don't rely on 850hPa temperatures to predict surface conditions as inversions are common under high pressure at this time of year.
To make things a little more fun we also run a competition in this thread throughout the year. This is by no means the only focus of the thread and you don't need to participate in the competition to post here. But it is a bit of fun which many of us enjoy.
The competition is run on a monthly basis and you can participate in just one or two or all of the months. For those who do take part throughout the year there is an annual competition which runs alongside the monthly competition. Full details below.
For those taking part in the competition all CET predictions for January should be sent directly to me via the forum private message system. Do not post them directly into the thread. You can also send me predictions for the average CET for 2019 as a whole if you wish.
The deadline for predictions this month is 2359 on Wednesday evening (2 January).
To keep things simple there will be no late submission penalty system as such going forward (I haven't actually applied any penalties for the past couple of years). The hard deadline for submissions will be the second of the month every month but you can make your prediction at any time before that. You can adjust your prediction once only each month prior to the deadline. Entries after 2359 on the 2nd of the month will only be accepted at my discretion if I consider there is a reasonable excuse.
Here is a reminder of how the CET competitions work for the benefit of everyone but also anyone who would like to join in for the first time. All are welcome to participate.
How do the competitions work?
Each month a new thread is opened a few days in advance of the start of a new month. Your challenge is to predict the mean Central England Temperature (CET) for the following month. The CET is the longest running temperature series and goes back to the mid 1600's. Each month I post some statistics about the CET for that month in recent years as well as a summary of some of the latest model output and long range forecasts to provide some context to assist you in making your prediction.
Predictions can be made either to one or two decimals (the actual data is published to two decimals). The closest person or persons to the final figure at the end of the month are declared the winner for that month. There are no prizes. This competition is just a bit of fun and the chance to amaze your fellow posters with your skill and foresight in predicting the weather (or you can just make a random guess!).
We use the Hadley data for the purposes of this competition which is maintained by the Met Office. Provisional figures are published daily with a final adjusted number usually issued on the first day of the following month.
In addition to the monthly competition there is an annual competition which runs throughout the year. The annual competition keeps a running total of the cumulative prediction errors from each month for each person. Absolute differences are used so it makes no difference if you overpredict or underpredict the CET in any given month. At the end of the year the person with the lowest cumulative prediction error after totalling each of the 12 months is declared the winner for the year. This is always a hard fought contest and requires a consistency of good predictions in order to win.
Summary of important points
- Predictions can be made up to 23:59 on the 2nd day of the month to which the prediction relates. No entries will generally be accepted after this time unless I am late in opening up the thread.
- All predictions should be made by private message to me.
- Once you have sent your prediction you are only permitted to change it once prior to the deadline. Any subsequent amendments will be ignored.
- You may make a prediction to either one or two decimals. You can predict the same figure as someone else.
- Where two members have the same cumulative prediction error for the year at the end of any month, the order of ranking in the competition table will be determined by which person has had the closest prediction to the actual CET in any month. If there is a still a tie I then look to the second closest prediction for each person and so on until the tie is broken. If the tie cannot be broken (very unlikely by December but can happen in the first couple of months of the year) then each person impacted is awarded the same position in the table.
If a person participating in the annual CET competition does not make a prediction in any one month (including January) their prediction error for that month will be calculated as follows:
- the upper quartile (75th percentile) of the prediction errors of all the people in the annual competition who did make a prediction for that month will be calculated at the end of the month;
The result of the above calculation will be used as the CET prediction error for any person who misses a prediction in a particular month subject to one further point:
- If, for any person, their average monthly prediction error for all the previous months in the year to date is higher than the 75th percentile of errors (for those that did make a prediction) in the month the person in question made no prediction, then the average prediction error will be substituted instead of the 75th percentile figure. This override is only likely to apply to those people towards the foot of the table who have very made very large errors in previous months.
One final important point. If you want to be included in the year long competition you may not miss more than two predictions during a calendar year. If a third prediction is missed that person will be eliminated from the annual competition (otherwise it would mean 25% or more of the annual error being calculated on non-existent predictions which would reduce the credibility of the competition too much). However, that person can continue to make predictions for the purpose of the monthly competition.
Now on to some data for January:
Historic CET summary for January
1971-2000 4.2C (30 years)
1981-2010 4.4C (30 years)
1999-2018 4.7C (last 20 years)
We have not had a cold January since 2013 and that was only 0.7C below the 1971-2000 mean. There have been three years above 5C recently - 2014, 2016 and 2018. Last very cold January was 2010 with 1.4C.
Here is a chart of the January CET for all years since 1961:
Direct link to larger version of the chart CHART
IMAGE. Members enable at bottom of page
Current model output (at 12z 29 Dec)
GFS (12z) - most ENS members suggesting generally above average 850 conditions for the first week of Jan apart from a dip on the 2nd. After that a bit of a spaghetti mess.
GEM (12z) - similar to GFS
Multi Op - fairly good agreement from all the models
The ECM ENS T2m temperatures for De Bilt look very consistent and mild for the first 2 weeks of Jan
Met Office contingency planners outlook
A higher than average probability of colder conditions
If we look at years with Nov CET close to 8C and Dec CET close to 7C we have the following matches:
2006 and 1953. Not surprising as very few Decembers close to 7C. Early 2007 was very mild while early 1954 was very cold. So no pattern there.
Widening the net to all years since 1950 with generally warm Novembers and Decembers we can add the following years to the mix:
1983, 1986, 1994, 1997, 2003, 2011, 2015
Apart from early 1987 (cold) and 1984 (cool) all of these years had a mild or very mild Jan / Feb following them.
So based purely on Nov / Dec temps the past would indicate that we could be in for a mild rest of the winter. But of course it is not as simple as that. Looking at broader conditions and I have said elsewhere, 1953 is currently an excellent match for 2018. That year saw conditions turn very cold in early 1954.
First look at January temperature tracker
IMAGE. Members enable at bottom of page
IMAGE. Members enable at bottom of page
Edited by moderator
02 March 2019 11:11:05
| Reason: Not specified