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Roger J Smith

December 2016 C.E.T. forecasts -- start of 2016-17 competition year

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Below is the December CET from 1659-2015 in blue, the 30 year average in red and the linear trend in black.

UvDmKcd.png

The CET this month is likely to finish somewhere between 5.5 and 6.1C after corrections. The average December following Novembers within that range is 3.8C.

The linear trend for the whole record is +0.38C per century. Following this trend gives a December CET of 4.8C.
The linear trend since 1850 is +0.65C per century. Following this trend gives a December CET of 5.0C.
The linear trend since 1950 is +1.16C per century. Following this trend gives a December CET of 5.1C.
The linear trend over the last 50 years is +0.49C per century. Following this trend gives a December CET of 5.0C.
The linear trend over the last 30 years is -0.29C per century. Following this trend gives a December CET of 4.9C.

The recent trend of cool Decembers has now been mostly nullified by last year. The trend from the last 30 years has switched from -4.4C/century last year to -0.3C/century this year. However, we probably won't have a shot at a new record high for the 30 year average as the mid 80s had some mild Decembers which are now leaving the 30 year period.
The standard deviation for December over the last 10 years has been the largest on record at 2.9C (previous highest was 1839-1848 at +2.54). This means the Decembers recently, as many might have guessed, have been the most variable across the entire CET record.

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This is a horrible forecast to make. High pressure likely to sit over us for a while (cold, becoming very cold). Will it sink ever so slightly and let in the gulf stream? Or will it join in with a potential split in the PV and allow NElys in? Or will it be undercut from the SW?

The latter idea seems a bit remote right now, so I think I'll side with the sinking high idea and a return to something milder mid-month. So 5.2C please. Hope I'm wrong though!

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Guess my edit upstream could be missed -

So I now want to go in at 3.3C.

Charts are looking even colder to me!

MIA

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The start to December at least is looking colder than normal, perhaps significantly so thanks to cold pooling at the surface.. key question how long will the high persevere, its a tall order to expect highs to stick in situ in December for perhaps more than 2 weeks, though unusually so we have had quite a few Decembers with such spells, Dec 1992 and 2002, more recently Dec 2006 and 2007 brought a 2 week high pressure spell. In all cases the high sunk, followed by very mild conditions. However, we do appear to be in a different state this year, with the very weak PV. With this in mind, I'm expecting it to hang around in some guise close to our shores preety much through the month, perhaps drawing in a temporary milder incursion, but then quickly putting a stop to that.

I'll go for a cold 2.9 degrees. Chance we may pull in some significant colder uppers last week of the month which could peg it back down a few tenths of a degree.

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On 25 November 2016 at 14:41, DR(S)NO said:

4 c please .......I think after the first week or so we will see Winter start up..... Quite convinced we will see some decent Winter weather this December ..... And my money is firmly where my mouth is with a small wager on a White Xmas

image.gif

After noting some of the longer range comments over on the model thread im now even more convinced we are likely to experience a great festive period.

im also reducing my guess to 2.5c please ....Brrrr

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start of dec is going to be cold but i don't think its going to last though this is the uk after all. so im going for 4.5c thanks.

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I'm going for a cold 3.1C please.

Edited by John88B
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