PLEASE SEND YOUR DECEMBER 2016 AND WINTER 2016/17 CET PREDICTIONS TO ME VIA PM PLEASE
I AM GOING TO RUN A WINTER CET COMPETITION SO IF YOU WANT TO PARTICIPATE PLEASE SEND ME YOUR PREDICTION AT THE SAME TIME AS YOUR DECEMBER PREDICTION
So we reach the end of another year and we move into another winter. Lots of speculation about whether the first half of this winter will be a cold one. We will soon find out. I rather suspect it will be on the chilly side.
As ever predictions for the final two months of the year are to be made by private message to me please rather than posted in this thread. This ensures we get genuine predictions not tactical predictions as the annual competition reaches its climax.
Predictions for December and for winter 2016/17 can be made until 23:59 on 2 December.
Historic summary for December
1971-2000 5.1C
1981-2010 4.6C
1996-2015 4.9C
Last December was of course the warmest on record by a country mile with an astonishing CET of 9.7C. No chance of seeing anything remotely similar this year. December 2010 was one of the coldest on record with -0.7C. 2011 and 2013 were both mild at 6.0C and 6.4C. Worth noting that December is the only month of the year where the 1971-2000 mean is higher than the 1981-2010 mean. The warm December last year does mean the rolling 20 year average for December is back to near 5C now.
Chart of December CET with rolling 10 year mean since 1961
Latest model output
After a cool start the 850's start to trend up quite significantly. But this can be deceptive at this time of year. High pressure will be in charge for potentially all of the first 10 days of the month and so at the surface temperatures are likely to remain cool - the MT2 links show this well. Maybe something a bit milder into the second week as low pressure moves towards the north west of the UK.
http://old.wetterzentrale.de/pics/MT8_London_ens.png
http://old.wetterzentrale.de/pics/MT2_London_ens.png
http://old.wetterzentrale.de/pics/MT2_Manchester_ens.png
http://old.wetterzentrale.de/pics/MT8_Manchester_ens.png
12z ECM looks cool to average at best. Control run is very cold and an outlier for a period before trending very mild. Huge scatter on the ENS by day 6 though so pointless in my view looking beyond T120 at the moment on these charts.
https://meteoijsselmuiden.nl/knmipluim
Met Office contingency planners
Significantly higher than normal risk of impacts from colder conditions. Rare to see this level of confidence in a contingency planners forecast. The chart for December is quite telling. Of course it is only a probabilistic assessment so does not mean we can't see an average or mild December. But the odds on this are relatively lower than normal.
http://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/public-sector/forecast-temp-djf-v1.pdf
November CET outlook based on current model runs
Will try and post this up on Tuesday evening
Analogue Arctic Oscillation (AO)
It looks like we will have seen at least 50 days in October and November this year with a AO index reading that is negative. I had a look back through the archives to see when was the last time at least 50 days were negative in Oct and Nov. I had to go back to 1968. That year saw a cold December with a CET of 3.0C. Not a great analogue though as we were entering a weak El Nino and close to a solar maximum.
Prior to that you have to go back to 1960. This year also saw a cool December but not quite as cold at 3.9C. This is a much better analogue. We were heading towards a solar minimum and we were in an ENSO neutral state. That winter saw a cool December and also a coolish January with a CET of just 3.5C up to the 27th. Beyond this February and March were very mild.
So 1960/61 looks like an interesting potential comparison. No exceptional cold but a chilly first 2 months of winter followed by a very mild last month of winter and first month of spring.
Pattern matching
Looking at combinations of average Octobers with cool Novembers with similar CETs to this year, 2010 is an obvious match. 1998 is close as well as is 1988. 1976, 1972, 1967, 1962, 1961 are also all close. 5 of those years all had cold Decembers whereas 2 were mild and one average. The last cold year was 1976.
Interestingly 1976 also had a winter pattern very similar to what I describe above for 1960 with a cold first 2 months followed by very mild February and March. 1976 was a solar minimum and had a weak El Nino so not a great match for this year.
But overall I think there are strong grounds to suggest that December really ought to be a cold month this year. Particularly when you also consider the weakness of the polar vortex, the record low sea ice, the strong hurricane season, bitter cold already established in Siberia (-50C in places at the moment so a good cold pool) and the record mild temperatures in the Arctic. All must favour the chances of increased blocking. Whether this blocking sets up correctly to allow cold to filter through to the UK is of course another matter. But the possibility is there and much greater chance than in most years. The synoptic set up this year is clearly hugely different to what it was in December last year.
Edited by moderator
30 January 2017 11:20:39
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Reason: Not specified