January CET

[osmposm]

I don't think 1991 had a sub-zero 31 day period, I think it's got to be Feb '86 for that, and before that early Dec 81- mid Jan 82. Sub-1ºC you are probably right with 1991.

Coldest 31 day periods of each winter (I think!):

1991 : 22 Jan - 21 Feb : +0.3 (rounded from 0.33)

1987 : 3 Jan - 2 Feb : +0.4 (rounded from 0.37)

1986 : 1 Feb - 3 Mar : -1.0 (rounded from 0.99)

1981-2 : 16 Dec - 15 Jan : -0.3

1978-9 : 30 Dec - 29 Jan : -0.5 (rounded from 0.54)

(Sorry - started doing this hours ago, and got waylaid...now see that in the meanwhile Snowmdn has done some of it already!)

Edited January 11, 2010 by osmposm

[kold weather]

Current CET is about -1.4c to the 10th. GFS suggests a mean temperature of 0.6c for the period 11th-15th giving a CET of -0.7c to the 15th.

For January to be the coldest on record, the second half would need to avergage -5.5c (9.7c below normal) (to give a final CET of -3.1c)

For January to be the warmest on record, the second half would need to average 15.7c (11.5c above normal) (To give a final CET 7.5c)

If the second half averaged;

0.0c= Final CET -0.4c

1.0c= 0.2c 15%

2.0c= 0.7c 25%

3.0c= 1.2c 30%

4.0c= 1.7c 35%

5.0c= 2.2c 45%

6.0c= 2.7c 60%

7.0c= 3.2c 40%

8.0c= 3.7c 10%

9.0= 4.2c 5%

As a rough guide, I've put in brackets in my view, the precentage of what's likely from here on in taking into account the recent big warming trend, previous corrects and the models.

For what it's worth 2.7c would be a good benchmark.

6.0C...really!

I think you could probably half that for the second half. I'm fully expecting pressure to build quite strongly near the UK, and to once again see cold SE/E winds, probably not 'that' cold relative but we shall see...best chance of getting 6C and above would come from the high being just a little too far east dragging up fairly mild southerly airflows.

Should see a slow warm-up of the CET, followed by a quicker one during the weekend however I'm expecting a fairly cold flow to come back in by the middle of the week, as I said nothing too extreme but on the below average side I'd guess.

I'd say between 1-2C is the most likely outcome, with 2-3C being the next likely one after that...anything above 3C is IMO out of the question given the trend thats developing on the models again.

[AderynCoch]

The first ten days of the month have beaten January 1941 by some distance, even with the inevitable revised figures come February. Very impressive indeed.

Mid-December to mid-January shouldn't beat 1981-2, but it should run it close:

16th December 1981 - 15th January 1982 = -0.3C

16th December 2009 - 10th January 2010 = -0.1C

Again, very impressive.

[damianslaw]

Interesting statistics with regard to the 31 day colder spells in 1986, 1991, I hope people don't believe we have endured the coldest sustained period of temperatures since 81/82 as the media keep saying, no we have not, 1986 and 1991 have beaten it. We've had the coldest sustained spell of weather relative to the time of year since 81/82 but not the coldest.

[Higher Ground]

Interesting statistics with regard to the 31 day colder spells in 1986, 1991, I hope people don't believe we have endured the coldest sustained period of temperatures since 81/82 as the media keep saying, no we have not, 1986 and 1991 have beaten it. We've had the coldest sustained spell of weather relative to the time of year since 81/82 but not the coldest.

I wouldn't be so sure whether 1986, and certainly 1991, will end up having beaten it in Scotland, or even in the north of England. Remember you're talking specifically about the CET. As for the temperature for the whole of the UK, it remains to be seen how this stacks up in terms of 31 day spells.

Edited January 11, 2010 by Higher Ground

[AderynCoch]

We've had the coldest sustained spell of weather relative to the time of year since 81/82 but not the coldest.

Very true, but that "relative to the time of year" bit is important.

Apart from 1981/2, I can think of only 1962/3 having a sub-zero mid-December to mid-January period in the last 100 years. This winter is tantalisingly close to joining an exclusive club.

[osmposm]

I wouldn't be so sure whether 1986, and certainly 1991, will end up having beaten it in Scotland, or even in the north of England. Remember you're talking specifically about the CET. As for the temperature for the whole of the UK, it remains to be seen how this stacks up in terms of 31 day spells.

Of course - but being a thread about the CET that's what we tend to talk about!

[Roger J Smith]

What's really remarkable is that there are stations in Ireland running sub-zero so far in January.

Meanwhile, in Florida, most stations have recorded anomalies of -8 C deg so far this month!

You can click here and see some of these astounding anomalies, and actually the 11th was colder than the first ten days, one station (Inverness) reported a low of 18 F which was seven lower than the old all-time record, dating back to 1948.

http://www.nws.noaa.gov/view/prodsByState.php?state=FL&prodtype=climate

I think the sun is perhaps in need of repair, the heat is broken all around the Atlantic.

Edited January 12, 2010 by Roger J Smith

[Higher Ground]

Of course - but being a thread about the CET that's what we tend to talk about!

But I was taking issue with someone assuming the CET represented the whole country's temperatures. Since Dec, the CET has been under-representative of the wider cold. For example, in both Scotland and Northern Ireland (as well as incidentally Ireland I understand) Dec 2009 was the coldest Dec since 1981 http://www.metoffice.gov.uk/climate/uk/2009/december.html unlike with the CET.

[Optimus Prime]

For Scotland mean minima was the 2nd lowest on record at -2.7c dating back to 1916. 1981 was the coldest at -3.8c. Overall with a mean of 0.3c it was the 3rd coldest after 1950 (-0.1c) and 1981 (-0.7c)

For England it was nothing spectacular. Marginally colder than 2001 and 2008.

[Weather-history]

For Scotland mean minima was the 2nd lowest on record at -2.7c dating back to 1916. 1981 was the coldest at -3.8c. Overall with a mean of 0.3c it was the 3rd coldest after 1950 (-0.1c) and 1981 (-0.7c)

There is something else that is not as obvious about December 2009 for Scotland, based on those figures it was the coldest month since February 1986

[Snowly does it]

Hadley at -1.2 (-1.24) to the 11th, yesterday a balmy 1.0 above freezing!

Last night was a little colder than the preceeding night at -0.5.

105.7 degrees required to get above 3 in 20 days - average of 5.3 per day (rounded up)

74.7 to get above 2 - average of 3.8 per day (rounded up)

[Weather-history]

The coldest first half to winter since 1981-82?

[BLAST FROM THE PAST]

For me last winter proved it, but this winter certainly has...we can and will and have had severe cold affect the UK for a 30+ day period. Farewell to the theory that we can't :unsure:

Its that darn jetstream you know...shifting south.

BFTP

[kold weather]

Yep I think this is probaby the first 30 day period in a long time where we have seen real severe cold being sustained, the 30 day average is pretty impressive!

Dec-Jan 2009 proved we could get 20 day spells akin to the strength of cold in the past, but this has surpassed that cold spell in every single area...

Anyway the very cold stuff now drawing to an end, should still remain pretty cold. After Friday we do pick up a somewhat milder flow with CET temps probably between 4-6C however this may not last all that long before we see temps drop a touch between 3-4C...after that and quite frankly anything could happen, from the return of very mild southerlies to a full blown 91 style easterly.

I suspect it'll be somewhat touch and go as to whether we get sub 2C...the coldest solution will still mean sub 0C is possible BUT IMO the most likely solution is a cool cloudy SE flow, with both brief spells of milder southerlies and colder easterlies but neither really winning out, as I said a second half CET between 3-4C IMO is the most likely call but could quite easily be a few degrees with side.

What can be said is the last 10 days have been very cold, bordering excepitonally cold, esp with regards to the length and the time of year.

[Roger J Smith]

Surely we deserve just one bog-standard inversion high to complete the march to sub-2.0 for the month. Can we just have a high from any direction, nobody's too choosy at this point, sit over the UK for three days around the 22nd to the 24th, radiate like crazy then get the heck out of the way for the inevitable full moon whatever storm? Thank you -- a man in another time zone.

[Snowly does it]

Manley now at -1.9 to the 12th - with Hadley likely to update to -1.0 or thereabouts today, there is a large discrepancy - so a downward correction cannot be ruled out at month end again!

[kold weather]

I think thats very likely SM, I wouldn't be all that surprised to see the CET be dropped by 0.2/0.3C at the end of the month depending how far apart the gap ends up of course...

Anyway we are now leaving the worst of the cold and we will see some moderation, esp at the weekend where we should get above 0C at last, however the models are somewhat suggestive of a high pressure building close to the UK and maybe even an easterly flow which will quite possibly result in another cold spell.

I still suspect we will see the second half come in below average and if that occurs then a CET below 2C is quite possible, though the first 3 days of the second half of the period probably will come in above average.

[reef]

Hadley is -1.1C to the 12th. Yesterday was only 0.5C.

Today will almost certainly be positive as the minima is down as just -0.1C.

An average of 4.0C is now required to reach 2.0C by the end of the month provisonally. Realistically with any downward adjustment we'd need close to 4.5C for the last 19 days, so already we need temperatures at average or above to exceed 2.0C. This grows even more when you see the projected temperatures over the next few days.

[kold weather]

Yep and unless we see a decently mild final week then below 2C does look increasingly possible, esp given the possible return of an easterly flow, however long that lasts is up in the air of course...sub 1C is still more then possible with a decent length easterly shot...

For now the next target is 1.5C...thats a severe winter month and needs 3.15C from now on to reach that target.

Anyway yep Reef we will come in slightly positive BUT many places in the CET zone are down around freezing even now and maxes are generally between 0-1C, so temps today should come out probably between 0-0.5C more then likely.

[Optimus Prime]

Manley now at -1.9 to the 12th - with Hadley likely to update to -1.0 or thereabouts today, there is a large discrepancy - so a downward correction cannot be ruled out at month end again!

They always and publicly admit they revise their data to tie in with historical to modern changes to keep things as accurate as possible. It's not that it can't be ruled out, it's certain there'll be a downward correction.

When you compare Manley to Hadley, Hadley (who constantly fiddle about with stations) are more Urban while Manley are situated in the countryside.

Manley;

Mean Max 1.2c (-5.4c)

Mean Min -5.0c (-6.8c)

Manley has the minima down for the 7th at -13.0c. Hadley had it at -7.4c....

[Roger J Smith]

On the current model runs, I could see this CET edging up to 0.5 by the 17th, then holding steady or maybe falling back a touch to the 22nd, then it's hang on Sloopy as it's very likely to warm up for 3-5 days around the end of the month. By then, sitting at 1.0 on the 25th, it would take an average of 6.17 to reach 2.0, not unthinkable, but about the high end of damage that could be done to a cold month near the end. More likely to be near 5 in that spell from my research index, so at 5 after the 1.0 benchmark, it gives you (whirr) 55/31 which is 1.8, then adjust that downward to 1.5 because 1.8 is my guess and we can't have that (it's in the e-mails).

[damianslaw]

Does anyone have statistics of months since Feb 91 that have recorded a CET below 3 degrees. I think the only 2 months being Dec 95 and Dec 96, not sure about Jan 97 and Feb 96 though.

I don't think any of these months were lower than 2 degrees though, very good chance that Jan 10 will turn out to be the coldest month since Feb 91, whether it can beat it remains to be seen..

[Snowly does it]

Does anyone have statistics of months since Feb 91 that have recorded a CET below 3 degrees. I think the only 2 months being Dec 95 and Dec 96, not sure about Jan 97 and Feb 96 though.

I don't think any of these months were lower than 2 degrees though, very good chance that Jan 10 will turn out to be the coldest month since Feb 91, whether it can beat it remains to be seen..

Dec 95 2.3

Feb 96 2.5

Dec 96 2.9

Jan 97 2.5

Those are the only 4 since Feb 91

[damianslaw]

Dec 95 2.3

Feb 96 2.5

Dec 96 2.9

Jan 97 2.5

Those are the only 4 since Feb 91

Thanks for these, I didn't realise that Feb 96 and Jan 97 were colder than Dec 96.