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Optimus Prime

December CET

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December is a strange month in that it has shown a significant cooling since 1989 and is the only month to do so.

Last December had a mean temperature of 3.1c which is 2.0c below normal and the coldest since 1996 (in some areas since 1995) For Scotland and Northern Ireland it was the coldest since 1981.

Warmest December on record; 1934 and 1974 at 8.1c

Coldest December on record 1890 at -0.8c

Cold first week then briefly milder but turning colder with the last 2 weeks of the month cold

1st week -0.6c

2nd week +5.5c

3rd week 0.4c

4th week 2.9c

Overall 2.0c and coldest since 1981.

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December's trend of the last two decades goes against the other months of the year in that during the 1990s and 2000s it averaged out very close to the long term average overall, of the whole of the 1900s at least, in stark comparison to the other months in the year, in particular most notably the other winter months of January and February which both saw their warmest decades in the entire CET series in the 1990s and 2000s.

December saw a generally very cold run in the 1960s, then it flipped around the turn of that decade and was mostly mild to very mild throughout the 1970s and 1980s, then has seen a general easing back towards average over the last 20 years. Since 1988, only two Decembers have been significantly mild with a CET over 6*C, (1994, 2006), and even then these were still nowhere near the record of 8.1*C, and not in the top 20 warmest ever either.

Last December was a cold one at 3.1*C, and 2008 was also quite chilly as well.

On the other side of the coin, January and February have shown a pattern a bit like December in delayed fashion. Jan and Feb saw a generally very cold run for about a decade from 1977-87, then flipped around 1988 and then both these months have been very mild throughout the 1990s and 2000s, with only rare exceptions.

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very cold start, brief milder interlude, then cold biting back as height rise again to the north :)

CET - 2.8

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My forcast is the same as my forcast in the Winter CET .

I made it a week ago - and I still can see no real reason for changing it now.

So its 1.9C for me after a very cold start.

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I expect a cold December, keeping in line with the trend of recent Decembers. Overall CET 2.9C for me please.

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Morning Folks

Well it looks like the cold is due to arrive a little quicker than I thought back in October, so for me the December CET depends on how a mild interlude would last...

I think I'll go for a CET of 2.6C

Cheers

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I think given what looks likely to occur with the Stratosphere its only a matter of time before the Atlantic kicks in which means we are going to have to make the most out of possibly a very cold first week. I'll go with 4.5C for now, believing that the PV will remerge stronger in the back half of the month and develop a much more zonal pattern towards the end of the month...but I'll err on the slightly below average side for now just in case it takes longer to develop then I expect.

Once this cold pattern breaksdown eventually its going to be tough to get anywhere near as much cold down again if the Stratosphere cools as much as progged...

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I think given what looks likely to occur with the Stratosphere its only a matter of time before the Atlantic kicks in which means we are going to have to make the most out of possibly a very cold first week. I'll go with 4.5C for now, believing that the PV will remerge stronger in the back half of the month and develop a much more zonal pattern towards the end of the month...but I'll err on the slightly below average side for now just in case it takes longer to develop then I expect.

Once this cold pattern breaksdown eventually its going to be tough to get anywhere near as much cold down again if the Stratosphere cools as much as progged...

You don't think that even with the PV, pressure could remain relatively high over Scandinavia next month? :cold:

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I must be crazy so may raise this prediction on the 29th, however i will go for 2.1C, 3C below average.

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You don't think that even with the PV, pressure could remain relatively high over Scandinavia next month? :cold:

Its certainly an option though even then I think all that does is delay what possibly will happen, for example I think something like that occured in the last 15 days or so of Jan 1996 but eventually the Atlantic got in during Feb. I don't think it'll take that long this time for that to occur but certainly its an option and if it does occur then a December CET of 3-4 would be a good punt IMO...but for now I'm just not confident enough to go as low as that. I may well need adjust rght at the end of the month so lets see...

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3.8c for me please, keeping in line with my winter forecast.

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Revising my guestimate down: 2.0C for me please. I think (hope!) the block will hold.

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Slightly below average- 4.4C.

A mild second half to the month with little chance of a white Xmas? I shall make my punt next week.

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Provisionally I'm going to say 2.2 - The coldest since 1981.

I think we start quite cold, possibly snowy. But the first week or ten day should generally see a somewhat milder spell with thaw and spells of heavy rain - Cold air never far away though and by mid month to Christmas back it comes from the east - Possibly quite severe in this phase due that unusually cold pool sitting over Scandinavia and northern Europe. Over Christmas high pressure probably becomes focused to the west/north-west, so northerly winds to end the year - Probably less in the way of snow, but severe frosts becoming the main problem. New Year could be snowy as low pressure starts to try and move in from the Atlantic.

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